A Triangulation Checklist Born From the Question; “Why NOT Use Close Relatives for Triangulation?”

One of my readers asked why we don’t use close relatives for triangulation.

This is a great question because not using close relatives for triangulation seems counter-intuitive.

I used to ask my kids and eventually my students and customers if they wanted the quick short answer or the longer educational answer.

The short answer is “because close relatives are too close to reliably form the third leg of the triangle.” Since you share so much DNA with close relatives, someone matching you who is identical by chance can also match them for exactly the same reason.

If you trust me and you’re good with that answer, wonderful. But I hope you’ll keep reading because there’s so much to consider, not to mention a few gotchas. I’ll share my methodology, techniques, and workarounds.

We’ll also discuss absolutely wonderful ways to utilize close relatives in the genetic genealogical process – just not for triangulation.

At the end of this article, I’ve provided a working triangulation checklist for you to use when evaluating your matches.

Let’s go!

The Step-by-Step Educational Answer😊

Some people see “evidence” they believe conflicts with the concept that you should not use close relatives for triangulation. I understand that, because I’ve gone down that rathole too, so I’m providing the “educational answer” that explains exactly WHY you should not use close relatives for triangulation – and what you should do.

Of course, we need to answer the question, “Who actually are close relatives?”

I’ll explain the best ways to best utilize close relatives in genetic genealogy, and why some matches are deceptive.

You’ll need to understand the underpinnings of DNA inheritance and also of how the different vendors handle DNA matching behind the scenes.

The purpose of autosomal DNA triangulation is to confirm that a segment is passed down from a particular ancestor to you and a specific set of your matches.

Triangulation, of course, implies 3, so at least three people must all match each other on a reasonably sized portion of the same DNA segment for triangulation to occur.

Matching just one person only provides you with one path to that common ancestor. It’s possible that you match that person due to a different ancestor that you aren’t aware of, or due to chance recombination of DNA.

It’s possible that your or your match inherited part of that DNA from your maternal side and part from your paternal side, meaning that you are matching that other person’s DNA by chance.

I wrote about identical by descent (IBD), which is an accurate genealogically meaningful match, and identical by chance (IBC) which is a false match, in the article Concepts – Identical by…Descent, State, Population and Chance.

I really want you to understand why close relatives really shouldn’t be used for triangulation, and HOW close relative matches should be used, so we’re going to discuss all of the factors that affect and influence this topic – both the obvious and little-understood.

  • Legitimate Matches
  • Inheritance and Triangulation
  • Parental Cross-Matching
  • Parental Phasing
  • Automatic Phasing at FamilyTreeDNA
  • Parental Phasing Caveats
  • Pedigree Collapse
  • Endogamy
  • How Many Identical-by-Chance Matches Will I Have?
  • DNA Doesn’t Skip Generations (Seriously, It Doesn’t)
  • Your Parents Have DNA That You Don’t (And How to Use It)
  • No DNA Match Doesn’t Mean You’re Not Related
  • Imputation
  • Ancestry Issues and Workarounds
  • Testing Close Relatives is VERY Useful – Just Not for Triangulation
  • Triangulated Matches
  • Building Triangulation Evidence – Ingredients and a Recipe
  • Aunts/Uncles
  • Siblings
  • How False Positives Work and How to Avoid Them
  • Distant Cousins Are Best for Triangulation & Here’s Why
  • Where Are We? A Triangulation Checklist for You!
  • The Bottom Line

Don’t worry, these sections are logical and concise. I considered making this into multiple articles, but I really want it in one place for you. I’ve created lots of graphics with examples to help out.

Let’s start by dispelling a myth.

DNA Doesn’t Skip Generations!

Recently, someone emailed to let me know that they had “stopped listening to me” in a presentation when I said that if a match did not also match one of your parents, it was a false match. That person informed me that they had worked on their tree for three years at Ancestry and they have “proof” of DNA skipping generations.

Nope, sorry. That really doesn’t happen, but there are circumstances when a person who doesn’t understand either how DNA works, or how the vendor they are using presents DNA results could misunderstand or misinterpret the results.

You can watch my presentation, RootsTech session, DNA Triangulation: What, Why and How, for free here. I’m thrilled that this session is now being used in courses at two different universities.

DNA really doesn’t skip generations. You CANNOT inherit DNA that your parents didn’t have.

Full stop.

Your children cannot inherit DNA from you that you don’t carry. If you don’t have that DNA, your children and their descendants can’t have it either, at least not from you. They of course do inherit DNA from their other parent.

I think historically, the “skipping generations” commentary was connected to traits. For example, Susie has dimples (or whatever) and so did her maternal grandmother, but her mother did not, so Susie’s dimples were said to have “skipped a generation.” Of course, we don’t know anything about Susie’s other grandparents, if Susie’s parents share ancestors, recessive/dominant genes or even how many genetic locations are involved with the inheritance of “dimples,” but I digress.

DNA skipping generations is a fallacy.

You cannot legitimately match someone that your parent does not, at least not through that parent’s side of the tree.

But here’s the caveat. You can’t match someone one of your parents doesn’t with the rare exception of:

  • Relatively recent pedigree collapse that occurs when you have the same ancestors on both sides of your tree, meaning your parents are related, AND
  • The process of recombination just happened to split and recombine a segment of DNA in segments too small for your match to match your parents individually, but large enough when recombined to match you.

We’ll talk about that more in a minute.

However, the person working with Ancestry trees can’t make this determination because Ancestry doesn’t provide segment information. Ancestry also handles DNA differently than other vendors, which we’ll also discuss shortly.

We’ll review all of this, but let’s start at the beginning and explain how to determine if our matches are legitimate, or not.

Legitimate Matches

Legitimate matches occur when the DNA of your ancestor is passed from that ancestor to their descendants, and eventually to you and a match in an unbroken pathway.

Unbroken means that every ancestor between you and that ancestor carried and then passed on the segment of the ancestor’s DNA that you carry today. The same is true for your match who carries the same segment of DNA from your common ancestor.

False positive matches occur when the DNA of a male and female combine randomly to look like a legitimate match to someone else.

Thankfully, there are ways to tell the difference.

Inheritance and Triangulation

Remember, you inherit two copies of each of your chromosomes 1-22, one copy from your mother and one from your father. You inherit half of the DNA that each parent carries, but it’s mixed together in you so the labs can’t readily tell which nucleotide, A, C, T, or G you received from which parent. I’m showing your maternal and paternal DNA in the graphic below, stacked neatly together in a column – but in reality, it could be AC in one position and CA in the next.

For matching all that matters is the nucleotide that matches your match is present in one of those two locations. In this case, A for your mother’s side and C for your father’s side. If you’re interested, you can read more about that in the article, Hit a Genealogy Home Run Using Your Double-Sided Two-Faced Chromosomes While Avoiding Imposters.

You can see in this example that you inherited all As from your Mom and all Cs from your Dad.

  • A legitimate maternal match would match you on all As on this particular example segment.
  • A legitimate paternal match would match you on all Cs on this particular segment.
  • A false positive match will match you on some random combination of As and Cs that make it look like they match you legitimately, but they don’t.
  • A false positive match will NOT match either your mother or your father.

To be very clear, technically a false positive match DOES match your DNA – but they don’t match your DNA because you share a common ancestor with your match. They match you because random recombination on their side causes you to match each other by chance.

In other words, if part of your DNA came from your Mom’s side and part from your Dad’s but it randomly fell in the correct positional order, you’d still match someone whose DNA was from only their mother or father’s side. That’s exactly the situation shown above and below.

Looking at our example again, it’s evident that your identical by chance (IBC) match’s A locations (1, 3, 5, 7 & 9) will match your Mom. C locations (2, 4, 6 8, & 10) will match your Dad, but the nonmatching segments interleaved in-between that match alternating parents will prevent your match from matching either of your parents. In other words, out of 10 contiguous locations in our example, your IBC match has 5 As alternated with 5 Cs, so they won’t match either of your parents who have 10 As or 10 Cs in a row.

This recombination effect can work in either direction. Either or both matching people’s DNA could be randomly mixed causing them to match each other, but not their parents.

Regardless of whose DNA is zigzagging back and forth between maternal and paternal, the match is not genealogical and does not confirm a common ancestor.

This is exactly why triangulation works and is crucial.

If you legitimately match a third person, shown below, on your maternal side, they will match you, your first legitimate maternal match, and your Mom because they carry all As. But they WON’T match the person who is matching you because they are identical by chance, shown in grey below.

The only person your identical by chance match matches in this group is you because they match you because of the chance recombination of parental DNA.

That third person WILL also match all other legitimate maternal matches on this segment.

In the graphic above, we see that while the grey identical by chance person matches you because of the random combination of As from your mother and Cs from your father, your legitimate maternal matches won’t match your identical by chance match.

This is the first step in identifying false matches.

Parental Cross-Matching

Removing the identical by chance match, and adding in the parents of your legitimate maternal match, we see that your maternal match, above, matches you because you both have all As inherited from one parent, not from a combination of both parents.

We know that because we can see the DNA of both parents of both matches in this example.

The ideal situation occurs when two people match and they have both had their parents tested. We need to see if each person matches the other person’s parents.

We can see that you do NOT match your match’s father and your match does NOT match your father.

You do match your match’s mother and your match does match your mother. I refer to this as Parental Cross-matching.

Your legitimate maternal matches will also match each other and your mother if she is available for testing.

All the people in yellow match each other, while the two parents in gray do not match any of your matches. An entire group of legitimate maternal matches on this segment, no matter how many, will all match each other.

If another person matches you and the other yellow people, you’ll still need to see if you match their parents, because if not, that means they are matching you on all As because their two parents DNA combined just happened, by chance, to contribute an A in all of those positions.

In this last example, your new match, in green, matches you, your legitimate match and both of your mothers, BUT, none of the four yellow people match either of the new match’s parents. You can see that the new green match inherited their As from the DNA of their mother and father both, randomly zigzagging back and forth.

The four yellow matches phase parentally as we just proved with cross matching to parents. The new match at first glance appears to be a legitimate match because they match all of the yellow people – but they aren’t because the yellow people don’t match the green person’s parents.

To tell the difference between legitimate matches and identical by chance matches, you need two things, in order.

  • Parental matching known as parental phasing along with parental cross-matching, if possible, AND
  • Legitimate identical by descent (IBD) triangulated matches

If you have the ability to perform parental matching, called phasing, that’s the easiest first step in eliminating identical by chance matches. However, few match pairs will have parents for everyone. You can use triangulation without parental phasing if parents aren’t available.

Let’s talk about both, including when and how close relatives can and cannot be used.

Parental Phasing

The technique of confirming your match to be legitimate by your match also matching one of your parents is called parental phasing.

If we have the parents of both people in a match pair available for matching, we can easily tell if the match does NOT match either parent. That’s Parental Cross Matching. If either match does NOT match one of the other person’s parents, the match is identical by chance, also known as a false positive.

See how easy that was!

If you, for example, is the only person in your match pair to have parents available, then you can parentally phase the match on your side if your match matches your parents. However, because your match’s parents are unavailable, your match to them cannon tbe verified as legitimate on their side. So you are not phased to their parents.

If you only have one of your parents available for matching, and your match does not match that parent, you CANNOT presume that because your match does NOT match that parent, the match is a legitimate match for the other, missing, parent.

There are four possible match conditions:

  • Maternal match
  • Paternal match
  • Matches neither parent which means the match is identical by chance meaning a false positive
  • Matches both parents in the case of pedigree collapse or endogamy

If two matching people do match one parent of both matches (parental cross-matching), then the match is legitimate. In other words, if we match, I need to match one of your parents and you need to match one of mine.

It’s important to compare your matches’ DNA to generationally older direct family members such as parents or grandparents, if that’s possible. If your grandparents are available, it’s possible to phase your matches back another generation.

Automatic Phasing at FamilyTreeDNA

FamilyTreeDNA automatically phases your matches to your parents if you test that parent, create or upload a GEDCOM file, and link your test and theirs to your tree in the proper places.

FamilyTreeDNA‘s Family Matching assigns or “buckets” your matches maternally and paternally. Matches are assigned as maternal or paternal matches if one or both parents have tested.

Additionally, FamilyTreeDNA uses triangulated matches from other linked relatives within your tree even if your parents have not tested. If you don’t have your parents, the more people you identify and link to your tree in the proper place, the more people will be assigned to maternal and paternal buckets. FamilyTreeDNA is the only vendor that does this. I wrote about this process in the article, Triangulation in Action at Family Tree DNA.

Parental Phasing Caveats

There are very rare instances where parental phasing may be technically accurate, but not genealogically relevant. By this, I mean that a parent may actually match one of your matches due to endogamy or a population level match, even if it’s considered a false positive because it’s not relevant in a genealogical timeframe.

Conversely, a parent may not match when the segment is actually legitimate, but it’s quite rare and only when pedigree collapse has occurred in a very specific set of circumstances where both parents share a common ancestor.

Let’s take a look at that.

Pedigree Collapse

It’s not terribly uncommon in the not-too-distant past to find first cousins marrying each other, especially in rather closely-knit religious communities. I encounter this in Brethren, Mennonite and Amish families often where the community was small and out-marrying was frowned upon and highly discouraged. These families and sometimes entire church congregations migrated cross-country together for generations.

When pedigree collapse is present, meaning the mother and father share a common ancestor not far in the past, it is possible to inherit half of one segment from Mom and the other half from Dad where those halves originated with the same ancestral couple.

For example, let’s say the matching segment between you and your match is 12 cM in length, shown below. You inherited the blue segment from your Dad and the neighboring peach segment from Mom – shown just below the segment numbers. You received 6 cM from both parents.

Another person’s DNA does match you, shown in the bottom row, but they are not shown on the DNA match list of either of your parents. That’s because the DNA segments of the parents just happened to recombine in 6 cM pieces, respectively, which is below the 7 cM matching threshold of the vendor in this example.

If the person matched you at 12 cM where you inherited 8 cM from one parent and 4 from the other, that person would show on one parent’s match list, but not the other. They would not be on the parent’s match list who contributed only 4 cM simply because the DNA divided and recombined in that manner. They would match you on a longer segment than they match your parent at 8 cM which you might notice as “odd.”

Let’s look at another example.

click to enlarge image

If the matching segment is 20 cM, the person will match you and both of your parents on different pieces of the same segment, given that both segments are above 7 cM. In this case, your match who matches you at 20 cM will match each of your parents at 10 cM.

You would be able to tell that the end location of Dad’s segment is the same as the start location of Mom’s segment.

This is NOT common and is NOT the “go to” answer when you think someone “should” match your parent and does not. It may be worth considering in known pedigree collapse situations.

You can see why someone observing this phenomenon could “presume” that DNA skipped a generation because the person matches you on segments where they don’t match your parent. But DNA didn’t skip anything at all. This circumstance was caused by a combination of pedigree collapse, random division of DNA, then random recombination in the same location where that same DNA segment was divided earlier. Clearly, this sequence of events is not something that happens often.

If you’ve uploaded your DNA to GEDmatch, you can select the “Are your parents related?” function which scans your DNA file for runs of homozygosity (ROH) where your DNA is exactly the same in both parental locations for a significant distance. This suggests that because you inherited the exact same sequence from both parents, that your parents share an ancestor.

If your parents didn’t inherit the same segment of DNA from both parents, or the segment is too short, then they won’t show as “being related,” even if they do share a common ancestor.

Now, let’s look at the opposite situation. Parental phasing and ROH sometimes do occur when common ancestors are far back in time and the match is not genealogically relevant.


I often see non-genealogical matching occur when dealing with endogamy. Endogamy occurs when an entire population has been isolated genetically for a long time. In this circumstance, a substantial part of the population shares common DNA segments because there were few original population founders. Much of the present-day population carries that same DNA. Many people within that population would match on that segment. Think about the Jewish community and indigenous Americans.

Consider our original example, but this time where much of the endogamous population carries all As in these positions because one of the original founders carried that nucleotide sequence. Many people would match lots of other people regardless of whether they are a close relative or share a distant ancestor.

People with endogamous lines do share relatives, but that matching DNA segment originated in ancestors much further back in time. When dealing with endogamy, I use parental phasing as a first step, if possible, then focus on larger matches, generally 20 cM or greater. Smaller matches either aren’t relevant or you often can’t tell if/how they are.

At FamilyTreeDNA, people with endogamy will find many people bucketed on the “Both” tab meaning they triangulate with people linked on both sides of the tester’s tree.

An example of a Jewish person’s bucketed matches based on triangulation with relatives linked in their tree is shown above.

Your siblings, their children, and your children will be related on both your mother’s and father’s sides, but other people typically won’t be unless you have experienced either pedigree collapse where you are related both maternally and paternally through the same ancestors or you descend from an endogamous population.

How Many Identical-by-Chance Matches Will I Have?

If you have both parents available to test, and you’re not dealing with either pedigree collapse or endogamy, you’ll likely find that about 15-20% of your matches don’t match your parents on the same segment and are identical by chance.

With endogamy, you’ll have MANY more matches on your endogamous lines and you’ll have some irrelevant matches, often referred to as “false positive” matches even though they technically aren’t, even using parental phasing.

Your Parents Have DNA That You Don’t

Sometimes people are confused when reviewing their matches and their parent’s match to the same person, especially when they match someone and their parent matches them on a different or an additional segment.

If you match someone on a specific segment and your parents do not, that’s a false positive FOR THAT SEGMENT. Every segment has its own individual history and should be evaluated individually. You can match someone on two segments, one from each parent. Or three segments, one from each parent and one that’s identical by chance. Don’t assume.

Often, your match will match both you and your parent on the same segment – which is a legitimate parentally phased match.

But what if your match matches your parent on a different segment where they don’t match you? That’s a false positive match for you.

Keep in mind that it is possible for one of your matches to match your parent on a separate or an additional segment that IS legitimate. You simply didn’t inherit that particular segment from your parent.

That’s NOT the same situation as someone matching you that does NOT match one of your parents on the same segment – which is an identical by chance or false match.

Your parent having a match that does not match you is the reverse situation.

I have several situations where I match someone on one segment, and they match my parent on the same segment. Additionally, that person matches my parent on another segment that I did NOT inherit from that parent. That’s perfectly normal.

Remember, you only inherit half of your parent’s DNA, so you literally did NOT inherit the other half of their DNA. Your mother, for example, should have twice as many matches as you on her side because roughly half of her matches won’t match you.

That’s exactly why testing your parents and close family members is so critical. Their matches are as valid and relevant to your genealogy as your own. The same is true for other relatives, such as aunts and uncles with whom you share ALL of the same ancestors.

You need to work with your family member’s matches that you don’t share.

No DNA Match Doesn’t Mean You’re Not Related

Some people think that not matching someone on a DNA test is equivalent to saying they aren’t related. Not sharing DNA doesn’t mean you’re not related.

People are often disappointed when they don’t match someone they think they should and interpret that to mean that the testing company is telling them they “aren’t related.” They are upset and take issue with this characterization. But that’s not what it means.

Let’s analyze this a bit further.

First, not sharing DNA with a second cousin once removed (2C1R) or more distant does NOT mean you’re NOT related to that person. It simply means you don’t share any measurable DNA ABOVE THE VENDOR THRESHOLD.

All known second cousins match, but about 10% of third cousins don’t match, and so forth on up the line with each generation further back in time having fewer cousins that match each other.

If you have tested close relatives, check to see if that cousin matches your relatives.

Second, it’s possible to match through the “other” or unexpected parent. I certainly didn’t think this would be the case in my family, because my father is from Appalachia and my mother’s family is primarily from the Netherlands, Germany, Canada, and New England. But I was wrong.

All it took was one German son that settled in Appalachia, and voila, a match through my mother that I surely thought should have been through my father’s side. I have my mother’s DNA and sure enough, my match that I thought should be on my father’s side matches Mom on the same segment where they match me, along with several triangulated matches. Further research confirmed why.

I’ve also encountered situations where I legitimately match someone on both my mother’s and father’s side, on different segments.

Third, imputation can be important for people who don’t match and think they should. Imputation can also cause matching segment length to be overreported.

Ok, so what’s imputation and why do I care?


Every DNA vendor today has to use some type of imputation.

Let me explain, in general, what imputation is and why vendors use it.

Over the years, DNA processing vendors who sell DNA chips to testing companies have changed their DNA chips pretty substantially. While genealogical autosomal tests test about 700,000 DNA locations, plus or minus, those locations have changed over time. Today, some of these chips only have 100,000 or so chip locations in common with chips either currently or previously utilized by other vendors.

The vendors who do NOT accept uploads, such as 23andMe or Ancestry, have to develop methods to make their newest customers on their DNA processing vendor’s latest chip compatible with their first customer who was tested on their oldest chip – and all iterations in-between.

Vendors who do accept transfers/uploads from other vendors have to equalize any number of vendors’ chips when their customers upload those files.

Imputation is the scientific way to achieve this cross-platform functionality and has been widely used in the industry since 2017.

Imputation, in essence, fills in the blanks between tested locations with the “most likely” DNA found in the human population based on what’s surrounding the blank location.

Think of the word C_T. There are a limited number of letters and words that are candidates for C_T. If you use the word in a sentence, your odds of accuracy increase dramatically. Think of a genetic string of nucleotides as a sentence.

Imputation can be incorrect and can cause both false positive and false negative matches.

For the most part, imputation does not affect close family matches as much as more distant matches. In other words, imputation is NOT going to cause close family members not to match.

Imputation may cause more distant family members not to match, or to have a false positive match when imputation is incorrect.

Imputation is actually MUCH less problematic than I initially expected.

The most likely effect of imputation is to cause a match to be just above or below the vendor threshold.

How can we minimize the effects of imputation?

  • Generally, the best result will be achieved if both people test at the same vendor where their DNA is processed on the same chip and less imputation is required.
  • Upload the results of both people to both MyHeritage and FamilyTreeDNA. If your match results are generally consistent at those vendors, imputation is not a factor.
  • GEDmatch does not use imputation but attempts to overcome files with low overlapping regions by allowing larger mismatch areas. I find their matches to be less accurate than at the various vendors.

Additionally, Ancestry has a few complicating factors.

Ancestry Issues

AncestryDNA is different in three ways.

  • Ancestry doesn’t provide segment information so it’s impossible to triangulate or identify the segment or chromosome where people match. There is no chromosome browser or triangulation tool.
  • Ancestry down-weights and removes some segments in areas where they feel that people are “too matchy.” You can read Ancestry’s white papers here and here.

These “personal pileup regions,” as they are known, can be important genealogically. In my case, these are my mother’s Acadian ancestors. Yes, this is an endogamous population and also suffers from pedigree collapse, but since this is only one of my mother’s great-grandparents, this match information is useful and should not be removed.

  • Ancestry doesn’t show matches in common if the shared segments are less than 20cM. Therefore, you may not see someone on a shared match list with a relative when they actually are a shared match.

If two people both match a third person on less than a 20 cM segment at Ancestry, the third person won’t appear on the other person’s shared match list. So, if I match John Doe on 19 cM of DNA, and I looked at the shared matches with my Dad, John Doe does NOT appear on the shared match list of me and my Dad – even though he is a match to both of us at 19 cM.

The only way to determine if John Doe is a shared match is to check my Dad’s and my match list individually, which means Dad and I will need to individually search for John Doe.

Caveat here – Ancestry’s search sometimes does not work correctly.

Might someone who doesn’t understand that the shared match list doesn’t show everyone who shares DNA with both people presume that the ancestral DNA of that ancestor “skipped a generation” because John Doe matches me with a known ancestor, and not Dad on our shared match list? I mean, wouldn’t you think that a shared match would be shown on a tab labeled “Shared Matches,” especially since there is no disclaimer?

Yes, people can be forgiven for believing that somehow DNA “skipped” a generation in this circumstance, especially if they are relatively inexperienced and they don’t understand Ancestry’s anomalies or know that they need to or how to search for matches individually.

Even if John Doe does match me and Dad both, we still need to confirm that it’s on the same segment AND it’s a legitimate match, not IBC. You can’t perform either of these functions at Ancestry, but you can elsewhere.

Ancestry WorkArounds

To obtain this functionality, people can upload their DNA files for free to both FamilyTreeDNA and MyHeritage, companies that do provide full shared DNA reporting (in common with) lists of ALL matches and do provide segment information with chromosome browsers. Furthermore, both provide triangulation in different ways.

Matching is free, but an inexpensive unlock is required at both vendors to access advanced tools such as Family Matching (bucketing) and triangulation at Family Tree DNA and phasing/triangulation at MyHeritage.

I wrote about Triangulation in Action at FamilyTreeDNA, here.

MyHeritage actually brackets triangulated segments for customers on their chromosome browser, including parents, so you get triangulation and parental phasing at the same time if you and your parent have both tested or uploaded your DNA file to MyHeritage. You can upload, for free, here.

In this example, my mother is matching to me in red on the entire length of chromosome 18, of course, and three other maternal cousins triangulate with me and mother inside the bracketed portion of chromosome 18. Please note that if any one of the people included in the chromosome browser comparison do not triangulate, no bracket is drawn around any others who do triangulate. It’s all or nothing. I remove people one by one to see if people triangulate – or build one by one with my mother included.

I wrote about Triangulation in Action at MyHeritage, here.

People can also upload to GEDmatch, a third-party site. While GEDmatch is less reliable for matching, you can adjust your search thresholds which you cannot do at other vendors. I don’t recommend routinely working below 7 cM. I occasionally use GEDmatch to see if a pedigree collapse segment has recombined below another vendor’s segment matching threshold.

Do NOT check the box to prevent hard breaks when selecting the One-to-One comparison. Checking that box allows GEDmatch to combine smaller matching segments into mega-segments for matching.

I wrote about Triangulation in Action at GEDmatch, here.

Transferring/Uploading Your DNA 

If you want to transfer your DNA to one of these vendors, you must download the DNA file from one vendor and upload it to another. That process does NOT remove your DNA file from the vendor where you tested, unless you select that option entirely separately.

I wrote full step-by-step transfer/upload instructions for each vendor, here.

Testing Close Relatives Is VERY Useful – Just Not for Triangulation

Of course, your best bet if you don’t have your parents available to test is to test as many of your grandparents, great-aunts/uncles, aunts, and uncles as possible. Test your siblings as well, because they will have inherited some of the same and some different segments of DNA from your parents – which means they carry different pieces of your ancestors’ DNA.

Just because close relatives don’t make good triangulation candidates doesn’t mean they aren’t valuable. Close relatives are golden because when they DO share a match with you, you know where to start looking for a common ancestor, even if your relative matches that person on a different segment than you do.

Close relatives are also important because they will share pieces of your common ancestor’s DNA that you don’t. Their matches can unlock the answers to your genealogy questions.

Ok, back to triangulation.

Triangulated Matches

A triangulated match is, of course, when three people all descended from a common ancestor and match each other on the same segment of DNA.

That means all three people’s DNA matches each other on that same segment, confirming that the match is not by chance, and that segment did descend from a common ancestor or ancestral couple.

But, is this always true? You’re going to hate this answer…

“It depends.”

You knew that was coming, didn’t you! 😊

It depends on the circumstances and relationships of the three people involved.

  • One of those three people can match the other two by chance, not by descent, especially if two of those people are close relatives to each other.
  • Identical by chance means that one of you didn’t inherit that DNA from one single parent. That zigzag phenomenon.
  • Furthermore, triangulated DNA is only valid as far back as the closest common ancestor of any two of the three people.

Let’s explore some examples.

Building Triangulation Evidence – Ingredients and a Recipe

The strongest case of triangulation is when:

  • You and at least two additional cousins match on the same segment AND
  • Descend through different children of the common ancestral couple

Let’s look at a valid triangulated match.

In this first example, the magenta segment of DNA is at least partially shared by four of the six cousins and triangulates to their common great-grandfather. Let’s say that these cousins then match with two other people descended from different children of their great-great-great-grandparents on this same segment. Then the entire triangulation group will have confirmed that segment’s origin and push the descent of that segment back another two generations.

These people all coalesce into one line with their common great-grandparents.

I’m only showing 3 generations in this triangulated match, but the concept is the same no matter how many generations you reach back in time. Although, over time, segments inherited from any specific ancestor become smaller and smaller until they are no longer passed to the next generation.

In this pedigree chart, we’re only tracking the magenta DNA which is passed generation to generation in descendants.

Eventually, of course, those segments become smaller and indistinguishable as they either aren’t passed on at all or drop below vendor matching thresholds.

This chart shows the average amount of DNA you would carry from each generational ancestor. You inherit half of each parent’s DNA, but back further than that, you don’t receive exactly half of any ancestor’s DNA in any generation. Larger segments are generally cut in two and passed on partially, but smaller segments are often either passed on whole or not at all.

On average, you’ll carry 7 cM of your eight-times-great-grandparents. In reality, you may carry more or you may not carry any – and you are unlikely to carry the same segment as any random other descendants but we know it happens and you’ll find them if enough (or the right) descendants test.

Putting this another way, if you divide all of your approximate 7000 cM of DNA into 7 cM segments of equal length – you’ll have 1000 7 cM segments. So will every other descendant of your eight-times-great-grandparent. You can see how small the chances are of you both inheriting that same exact 7 cM segment through ten inheritance/transmission events, each. Yet it does happen.

I have several triangulated matches with descendants of Charles Dodson and his wife, Anne through multiple of their 9 (or so) children, ten generations back in my tree. Those triangulated matches range from 7-38 cM. It’s possible that those three largest matches at 38 cM could be related through multiple ancestors because we all have holes in our trees – including Anne’s surname.

Click to enlarge image

It helps immensely that Charles Dodson had several children who were quite prolific as well.

Of course, the further back in time, the more “proof” is necessary to eliminate other unknown common ancestors. This is exactly why matching through different children is important for triangulation and ancestor confirmation.

The method we use to confirm the common ancestor is that all of the descendants who match the tester on the same segment all also match each other. This greatly reduces the chances that these people are matching by chance. The more people in the triangulation group, the stronger the evidence. Of course, parental phasing or cross-matching, where available is an added confirmation bonus.

In our magenta inheritance example, we saw that three of the males and one of the females from three different descendants of the great-grandparents all carry at least a portion of that magenta segment of great-grandpa’s DNA.

Now, let’s take a look at a different scenario.

Why can’t siblings or close relatives be used as two of the three people needed for triangulation?

Aunts and Uncles

We know that the best way to determine if a match is valid is by parental phasing – your match also matching to one of your parents.

If both parents aren’t available, looking for close family matches in common with your match is the next hint that genealogists seek.

Let’s say that you and your match both match your aunt or uncle in common or their children.

You and your aunts or uncles matching DNA only pushes your common ancestor back to your grandparents.

At that point, your match is in essence matching to a segment that belongs to your grandparents. Your matches’ DNA, or your grandparents’ DNA could have randomly recombined and you and your aunt/cousins could be matching that third person by chance.

Ok, then, what about siblings?


The most recent common ancestor (MRCA) of you and someone who also matches your sibling is your parents. Therefore, you and your sibling actually only count as one “person” in this scenario. In essence, it’s the DNA of your parent(s) that is matching that third person, so it’s not true triangulation. It’s the same situation as above with aunts/uncles, except the common ancestor is closer than your grandparents.

The DNA of your parents could have recombined in both siblings to look like a match to your match’s family. Or vice versa. Remember Parental Cross-Matching.

If you and a sibling inherited EXACTLY the same segment of your Mom’s and Dad’s DNA, and you match someone by chance – that person will match your sibling by chance as well.

In this example, you can see that both siblings 1 and 2 inherited the exact same segments of DNA at the same locations from both of their parents.

Of course, they also inherited segments at different locations that we’re not looking at that won’t match exactly between siblings, unless they are identical twins. But in this case, the inherited segments of both siblings will match someone whose DNA randomly combined with green or magenta dots in these positions to match a cross-section of both parents.

How False Positives Work and How to Avoid Them

We saw in our first example, displayed again above, what a valid triangulated match looks like. Now let’s expand this view and take a look more specifically at how false positive matches occur.

On the left-hand (blue) side of this graphic, we see four siblings that descend through their father from Great-grandpa who contributed that large magenta segment of DNA. That segment becomes reduced in descendants in subsequent generations.

In downstream generations, we can see gold, white and green segments being added to the DNA inherited by the four children from their ancestor’s spouses. Dad’s DNA is shown on the left side of each child, and Mom’s on the right.

  • Blue Children 1 and 2 inherited the same segments of DNA from Mom and Dad. Magenta from Dad and green from Mom.
  • Blue Child 3 inherited two magenta segments from Dad in positions 1 and 2 and one gold segment from Dad in position 3. They inherited all white segments from Mom.
  • Blue Child 4 inherited all gold segments from Dad and all white segments from Mom.

The family on the blue left-hand side is NOT related to the pink family shown at right. That’s important to remember.

I’ve intentionally constructed this graphic so that you can see several identical by chance (IBC) matches.

Child 5, the first pink sibling carries a white segment in position 1 from Dad and gold segments in positions 2 and 3 from Dad. From Mom, they inherited a green segment in position 1, magenta in position 2 and green in position 3.

IBC Match 1 – Looking at the blue siblings, we see that based on the DNA inherited from Pink Child 5’s parents, Pink Child 5 matches Blue Child 4 with white, gold and gold in positions 1-3, even though they weren’t inherited from the same parent in Blue Child 4. I circled this match in blue.

IBC Match 2 – Pink Child 5 also matches Blue Children 1 and 2 (red circles) because Pink Child 5 has green, magenta, and green in positions 1-3 and so do Blue Children 1 and 2. However, Blue Children 1 and 2 inherited the green and magenta segments from Mom and Dad respectively, not just from one parent.

Pink Child 5 matches Blue Children 1, 2 and 4, but not because they match by descent, but because their DNA zigzags back and forth between the blue children’s DNA contributed by both parents.

Therefore, while Pink Child 5 matches three of the Blue Children, they do not match either parent of the Blue Children.

IBC Match 3 – Pink Child 6 matches Blue Child 3 with white, magenta and gold in positions 1-3 based on the same colors of dots in those same positions found in Blue Child 3 – but inherited both paternally and maternally.

You can see that if we had the four parents available to test, that none of the Pink Children would match either the Blue Children’s mother or father and none of the Blue Children would match either of the Pink Children’s mother or father.

This is why we can’t use either siblings or close family relatives for triangulation.

Distant Cousins Are Best for Triangulation & Here’s Why

When triangulating with 3 people, the most recent common ancestor (MRCA) intersection of the closest two people is the place at which triangulation turns into only two lines being compared and ceases being triangulation. Triangle means 3.

If siblings are 2 of the 3 matching people, then their parents are essentially being compared to the third person.

If you, your aunt/uncle, and a third person match, your grandparents are the place in your tree where three lines converge into two.

The same holds true if you’re matching against a sibling pair on your match’s side, or a match and their aunt/uncle, etc.

The further back in your tree you can push that MRCA intersection, the more your triangulated match provides confirming evidence of a common ancestor and that the match is valid and not caused by random recombination.

That’s exactly what the descendants of Charles Dodson have been able to do through triangulation with multiple descendants from several of his children.

It’s also worth mentioning at this point that the reason autosomal DNA testing uses hundreds/thousands of base pairs in a comparison window and not 3 or 6 dots like in my example is that the probability of longer segments of DNA simply randomly matching by chance is reduced with length and SNP density which is the number of SNP locations tested within that cM range.

Hence a 7 cM/500 SNP minimum is the combined rule of thumb. At that level, roughly half of your matches will be valid and half will be identical by chance unless you’re dealing with endogamy. Then, raise your threshold accordingly.

Ok, So Where are We? A Triangulation Checklist for You!

I know this has been a relatively long educational article, but it’s important to really understand that testing close relatives is VERY important, but also why we can’t effectively use them for triangulation.

Here’s a handy-dandy summary matching/triangulation checklist for you to use as you work through your matches.

  • You inherit half of each of your parents’ DNA. There is no other place for you to obtain or inherit your DNA. There is no DNA fairy sprinkling you with DNA from another source:)
  • DNA does NOT skip generations, although in occasional rare circumstances, it may appear that this happened. In this situation, it’s incumbent upon you, the genealogist, to PROVE that an exception has occurred if you really believe it has. Those circumstances might be pedigree collapse or perhaps imputation. You’ll need to compare matches at vendors who provide a chromosome browser, triangulation, and full shared match list information. Never assume that you are the exception without hard and fast proof. We all know about assume, right?
  • Your siblings inherit half of your parents’ DNA too, but not the same exact half of your parent’s DNA that you other siblings did (unless they are identical twins.) You may inherit the exact same DNA from either or both of your parents on certain segments.
  • Your matches may match your parents on different or an additional segment that you did not inherit.
  • Every segment has an individual history. Evaluate every matching segment separately. One matching segment with someone could be maternal, one paternal, and one identical by chance.
  • You can confirm matches as valid if your match matches one of your parents, and you match one of your match’s parents. Parental Phasing is when your match matches your parent. Parental Cross-Matching is when you both match one of each other’s parents. To be complete, both people who match each other need to match one of the parents of the other person. This rule still holds even if you have a known common ancestor. I can’t even begin to tell you how many times I’ve been fooled.
  • 15-20% (or more with endogamy) of your matches will be identical by chance because either your DNA or your match’s DNA aligns in such a way that while they match you, they don’t match either of your parents.
  • Your siblings, aunts, and uncles will often inherit the same DNA as you – which means that identical by chance matches will also match them. That’s why we don’t use close family members for triangulation. We do utilize close family members to generate common match hints. (Remember the 20 cM shared match caveat at Ancestry)
  • While your siblings, aunts, and uncles are too close to use for triangulation, they are wonderful to identify ancestral matches. Some of their matches will match you as well, and some will not because your close family members inherited segments of your ancestor’s DNA that you did not. Everyone should test their oldest family members.
  • Triangulate your close family member’s matches separately from your own to shed more light on your ancestors.
  • Endogamy may interfere with parental phasing, meaning you may match because you and/or your match may have inherited some of the same DNA segment(s) from both sides of your tree and/or more DNA than might otherwise be expected.
  • Pedigree collapse needs to be considered when using parental phasing, especially when the same ancestor appears on both sides of your family tree. You may share more DNA with a match than expected.
  • Conversely, with pedigree collapse, your match may not match your parents, or vice versa, if a segment happens to have recombined in you in a way that drops the matching segments of your parents beneath the vendor’s match threshold.
  • While you will match all of your second cousins, you will only match approximately 90% of your third cousins and proportionally fewer as your relationship reaches further back in time.
  • Not being a DNA match with someone does NOT mean you’re NOT related to them, unless of course, you’re a second cousin (2C) or closer. It simply means you don’t carry any common ancestral segments above vendor thresholds.
  • At 2C or closer, if you’re not a DNA match, other alternative situations need to be considered – including the transfer/upload of the wrong person’s DNA file.
  • Imputation, a scientific process required of vendors may interfere with matching, especially in more distant relatives who have tested on different platforms.
  • Imputation artifacts will be less obvious when people are more closely related, meaning closer relatives can be expected to match on more and larger segments and imputation errors make less difference.
  • Imputation will not cause close relatives, meaning 2C or closer, to not match each other.
  • In addition to not supporting segment matching information, Ancestry down-weights some segments, removes some matching DNA, and does not show shared matches below 20cM, causing some people to misinterpret their lack of common matches in various ways.
  • To resolve questions about matching issues at Ancestry, testers can transfer/upload their DNA files to MyHeritage, FamilyTreeDNA, and GEDmatch and look for consistent matches on the same segment. Start and end locations may vary to some extent between vendors, but the segment size should be basically in the same location and roughly the same size.
  • GEDmatch does not use imputation but allows larger non-matching segments to combine as a single segment which sometimes causes extremely “generous” matches. GEDmatch matching is less reliable than FamilyTreeDNA or MyHeritage, but you can adjust the matching thresholds.
  • The best situation for matching is for both people to test at the same vendor who supports and provides segment data and a chromosome browser such as 23andMe, FamilyTreeDNA, or MyHeritage.
  • Siblings cannot be used for triangulation because the most recent common ancestor (MRCA) between you and your siblings is your parents. Therefore, the “three” people in the triangulation group is reduced to two lines immediately.
  • Uncles and aunts should not be used for triangulation because the most recent common ancestors between you and your aunts and uncles are your grandparents.
  • Conversely, you should not consider triangulating with siblings and close family members of your matches as proof of an ancestral relationship.
  • A triangulation group of 3 people is only confirmation as far back as when two of those people’s lines converge and reach a common ancestor.
  • Identical by chance (IBC) matching occurs when DNA from the maternal and paternal sides are mixed positionally in the child to resemble a maternal/paternal side match with someone else.
  • Identical by chance DNA admixture (when compared to a match) could have occurred in your parents or grandparent’s generation, or earlier, so the further back in time that people in a triangulation group reach, the more reliable the triangulation group is likely to be.
  • The larger the segments and/or the triangulation group, the stronger the evidence for a specific confirmed common ancestor.
  • Early families with a very large number of descendants may have many matching and triangulated members, even 9 or 10 generations later.
  • While exactly 50% of each ancestor’s DNA is not passed in each generation, on average, you will carry 7 cM of your ancestors 10 generations back in your tree. However, you may carry more, or none.
  • The percentage of matching descendants decreases with each generation beyond great-grandparents.
  • The ideal situation for triangulation is a significant number of people, greater than three, who match on the same reasonably sized segment (7 cM/500 SNP or larger) and descend from the same ancestor (or ancestral couple) through different children whose spouses in descendant generations are not also related.
  • This means that tree completion is an important factor in match/triangulation reliability.
  • Triangulating through different children of the ancestral couple makes it significantly less likely that a different unknown common ancestor is contributing that segment of DNA – like an unknown wife in a descendant generation.


The Bottom Line

Here’s the bottom line.

  1. Don’t use close relatives to triangulate.
  2. Use parents for Parental Phasing.
  3. Use Parental Cross-Matching when possible.
  4. Use close relatives to look for shared common matches that may lead to triangulation possibilities.
  5. Triangulate your close relatives’ DNA in addition to your own for bonus genealogical information. They will match people that you don’t.
  6. For the most reliable triangulation results, use the most distant relatives possible, descended through different children of the common ancestral couple.
  7. Keep this checklist of best practices, cautions, and caveats handy and check the list as necessary when evaluating the strength of any match or triangulation group. It serves as a good reminder for what to check if something seems “off” or unusual.

Feel free to share and pass this article (and checklist) on to your genealogy buddies and matches as you explain triangulation and collaborate on your genealogy.

Have fun!!!



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Y DNA: Step-by-Step Big Y Analysis

Many males take the Big Y-700 test offered by FamilyTreeDNA, so named because testers receive the most granular haplogroup SNP results in addition to 700+ included STR marker results. If you’re not familiar with those terms, you might enjoy the article, STRs vs SNPs, Multiple DNA Personalities.

The Big Y test gives testers the best of both, along with contributing to the building of the Y phylotree. You can read about the additions to the Y tree via the Big Y, plus how it helped my own Estes project, here.

Some men order this test of their own volition, some at the request of a family member, and some in response to project administrators who are studying a specific topic – like a particular surname.

The Big Y-700 test is the most complete Y DNA test offered, testing millions of locations on the Y chromosome to reveal mutations, some unique and never before discovered, many of which are useful to genealogists. The Big Y-700 includes the traditional Y DNA STR marker testing along with SNP results that define haplogroups. Translated, both types of test results are compared to other men for genealogy, which is the primary goal of DNA testing.

Being a female, I often recruit males in my family surname lines and sponsor testing. My McNiel line, historic haplogroup R-M222, has been particularly frustrating both genealogically as well as genetically after hitting a brick wall in the 1700s. My McNeill cousin agreed to take a Big Y test, and this analysis walks through the process of understanding what those results are revealing.

After my McNeill cousin’s Big Y results came back from the lab, I spent a significant amount of time turning over every leaf to extract as much information as possible, both from the Big Y-700 DNA test itself and as part of a broader set of intertwined genetic information and genealogical evidence.

I invite you along on this journey as I explain the questions we hoped to answer and then evaluate Big Y DNA results along with other information to shed light on those quandaries.

I will warn you, this article is long because it’s a step-by-step instruction manual for you to follow when interpreting your own Big Y results. I’d suggest you simply read this article the first time to get a feel for the landscape, before working through the process with your own results. There’s so much available that most people leave laying on the table because they don’t understand how to extract the full potential of these test results.

If you’d like to read more about the Big Y-700 test, the FamilyTreeDNA white paper is here, and I wrote about the Big Y-700 when it was introduced, here.

You can read an overview of Y DNA, here, and Y DNA: The Dictionary of DNA, here.

Ok, get yourself a cuppa joe, settle in, and let’s go!

George and Thomas McNiel – Who Were They?

George and Thomas McNiel appear together in Spotsylvania County, Virginia records. Y DNA results, in combination with early records, suggest that these two men were brothers.

I wrote about discovering that Thomas McNeil’s descendant had taken a Y DNA test and matched George’s descendants, here, and about my ancestor George McNiel, here.

McNiel family history in Wilkes County, NC, recorded in a letter written in 1898 by George McNiel’s grandson tells us that George McNiel, born about 1720, came from Scotland with his two brothers, John and Thomas. Elsewhere, it was reported that the McNiel brothers sailed from Glasgow, Scotland and that George had been educated at the University of Edinburgh for the Presbyterian ministry but had a change of religious conviction during the voyage. As a result, a theological tiff developed that split the brothers.

George, eventually, if not immediately, became a Baptist preacher. His origins remain uncertain.

The brothers reportedly arrived about 1750 in Maryland, although I have no confirmation. By 1754, Thomas McNeil appeared in the Spotsylvania County, VA records with a male being apprenticed to him as a tailor. In 1757, in Spotsylvania County, the first record of George McNeil showed James Pey being apprenticed to learn the occupation of tailor.

If George and Thomas were indeed tailors, that’s not generally a country occupation and would imply that they both apprenticed as such when they were growing up, wherever that was.

Thomas McNeil is recorded in one Spotsylvania deed as being from King and Queen County, VA. If this is the case, and George and Thomas McNiel lived in King and Queen, at least for a time, this would explain the lack of early records, as King and Queen is a thrice-burned county. If there was a third brother, John, I find no record of him.

My now-deceased cousin, George McNiel, initially tested for the McNiel Y DNA and also functioned for decades as the family historian. George, along with his wife, inventoried the many cemeteries of Wilkes County, NC.

George believed through oral history that the family descended from the McNiel’s of Barra.

McNiel Big Y Kisumul

George had this lovely framed print of Kisimul Castle, seat of the McNiel Clan on the Isle of Barra, proudly displayed on his wall.

That myth was dispelled with the initial DNA testing when our line did not match the Barra line, as can be seen in the MacNeil DNA project, much to George’s disappointment. As George himself said, the McNiel history is both mysterious and contradictory. Amen to that, George!

McNiel Big Y Niall 9 Hostages

However, in place of that history, we were instead awarded the Niall of the 9 Hostages badge, created many years ago based on a 12 marker STR result profile. Additionally, the McNiel DNA was assigned to haplogroup R-M222. Of course, today’s that’s a far upstream haplogroup, but 15+ years ago, we had only a fraction of the testing or knowledge that we do today.

The name McNeil, McNiel, or however you spell it, resembles Niall, so on the surface, this made at least some sense. George was encouraged by the new information, even though he still grieved the loss of Kisimul Castle.

Of course, this also caused us to wonder about the story stating our line had originated in Scotland because Niall of the 9 Hostages lived in Ireland.

Niall of the 9 Hostages

Niall of the 9 Hostages was reportedly a High King of Ireland sometime between the 6th and 10th centuries. However, actual historical records place him living someplace in the mid-late 300s to early 400s, with his death reported in different sources as occurring before 382 and alternatively about 411. The Annals of the Four Masters dates his reign to 379-405, and Foras Feasa ar Eirinn says from 368-395. Activities of his sons are reported between 379 and 405.

In other words, Niall lived in Ireland about 1500-1600 years ago, give or take.


Generally, migration was primarily from Scotland to Ireland, not the reverse, at least as far as we know in recorded history. Many Scottish families settled in the Ulster Plantation beginning in 1606 in what is now Northern Ireland. The Scots-Irish immigration to the states had begun by 1718. Many Protestant Scottish families immigrated from Ireland carrying the traditional “Mc” names and Presbyterian religion, clearly indicating their Scottish heritage. The Irish were traditionally Catholic. George could have been one of these immigrants.

We have unresolved conflicts between the following pieces of McNeil history:

  • Descended from McNeil’s of Barra – disproved through original Y DNA testing.
  • Immigrated from Glasgow, Scotland, and schooled in the Presbyterian religion in Edinburgh.
  • Descended from the Ui Neill dynasty, an Irish royal family dominating the northern half of Ireland from the 6th to 10th centuries.

Of course, it’s possible that our McNiel/McNeil line could have been descended from the Ui Neill dynasty AND also lived in Scotland before immigrating.

It’s also possible that they immigrated from Ireland, not Scotland.

And finally, it’s possible that the McNeil surname and M222 descent are not related and those two things are independent and happenstance.

A New Y DNA Tester

Since cousin George is, sadly, deceased, we needed a new male Y DNA tester to represent our McNiel line. Fortunately, one such cousin graciously agreed to take the Big Y-700 test so that we might, hopefully, answer numerous questions:

  • Does the McNiel line have a unique haplogroup, and if so, what does it tell us?
  • Does our McNiel line descend from Ireland or Scotland?
  • Where are our closest geographic clusters?
  • What can we tell by tracing our haplogroup back in time?
  • Do any other men match the McNiel haplogroup, and what do we know about their history?
  • Does the Y DNA align with any specific clans, clan history, or prehistory contributing to clans?

With DNA, you don’t know what you don’t know until you test.

Welcome – New Haplogroup

I was excited to see my McNeill cousin’s results arrive. He had graciously allowed me access, so I eagerly took a look.

He had been assigned to haplogroup R-BY18350.

McNiel Big Y branch

Initially, I saw that indeed, six men matched my McNeill cousin, assigned to the same haplogroup. Those surnames were:

  • Scott
  • McCollum
  • Glass
  • McMichael
  • Murphy
  • Campbell

Notice that I said, “were.” That’s right, because shortly after the results were returned, based on markers called private variants, Family Tree DNA assigned a new haplogroup to my McNeill cousin.

Drum roll please!!!

Haplogroup R-BY18332

McNiel Big Y BY18332

Additionally, my cousin’s Big Y test resulted in several branches being split, shown on the Block Tree below.

McNIel Big Y block tree

How cool is this!

This Block Tree graphic shows, visually, that our McNiel line is closest to McCollum and Campbell testers, and is a brother clade to those branches showing to the left and right of our new R-BY18332. It’s worth noting that BY25938 is an equivalent SNP to BY18332, at least today. In the future, perhaps another tester will test, allowing those two branches to be further subdivided.

Furthermore, after the new branches were added, Cousin McNeill has no more Private Variants, which are unnamed SNPs. There were all utilized in naming additional tree branches!

I wrote about the Big Y Block Tree here.

Niall (Or Whoever) Was Prolific

The first thing that became immediately obvious was how successful our progenitor was.

McNiel Big Y M222 project

click to enlarge

In the MacNeil DNA project, 38 men with various surname spellings descend from M222. There are more in the database who haven’t joined the MacNeil project.

Whoever originally carried SNP R-M222, someplace between 2400 and 5900 years ago, according to the block tree, either had many sons who had sons, or his descendants did. One thing is for sure, his line certainly is in no jeopardy of dying out today.

The Haplogroup R-M222 DNA Project, which studies this particular haplogroup, reads like a who’s who of Irish surnames.

Big Y Match Results

Big Y matches must have no more than 30 SNP differences total, including private variants and named SNPs combined. Named SNPs function as haplogroup names. In other words, Cousin McNeill’s terminal SNP, meaning the SNP furthest down on the tree, R-BY18332, is also his haplogroup name.

Private variants are mutations that have occurred in the line being tested, but not yet in other lines. Occurrences of private variants in multiple testers allow the Private Variant to be named and placed on the haplotree.

Of course, Family Tree DNA offers two types of Y DNA testing, STR testing which is the traditional 12, 25, 37, 67 and 111 marker testing panels, and the Big Y-700 test which provides testers with:

  • All 111 STR markers used for matching and comparison
  • Another 589+ STR markers only available through the Big Y test increasing the total STR markers tested from 111 to minimally 700
  • A scan of the Y chromosome, looking for new and known SNPs and STR mutations

Of course, these tests keep on giving, both with matching and in the case of the Big Y – continued haplogroup discovery and refinement in the future as more testers test. The Big Y is an investment as a test that keeps on giving, not just a one-time purchase.

I wrote about the Big Y-700 when it was introduced here and a bit later here.

Let’s see what the results tell us. We’ll start by taking a look at the matches, the first place that most testers begin.

Mcniel Big Y STR menu

Regular Y DNA STR matching shows the results for the STR results through 111 markers. The Big Y section, below, provides results for the Big Y SNPs, Big Y matches and additional STR results above 111 markers.

McNiel Big Y menu

Let’s take a look.

STR and SNP Testing

Of Cousin McNeil’s matches, 2 Big Y testers and several STR testers carry some variant of the Neal, Neel, McNiel, McNeil, O’Neil, etc. surnames by many spellings.

While STR matching is focused primarily on a genealogical timeframe, meaning current to roughly 500-800 years in the past, SNP testing reaches much further back in time.

  • STR matching reaches approximately 500-800 years.
  • Big Y matching reaches approximately 1500 years.
  • SNPs and haplogroups reach back infinitely, and can be tracked historically beyond the genealogical timeframe, shedding light on our ancestors’ migration paths, helping to answer the age-old question of “where did we come from.”

These STR and Big Y time estimates are based on a maximum number of mutations for testers to be considered matches paired with known genealogy.

Big Y results consider two men a match if they have 30 or fewer total SNP differences. Using NGS (next generation sequencing) scan technology, the targeted regions of the Y chromosome are scanned multiple times, although not all regions are equally useful.

Individually tested SNPs are still occasionally available in some cases, but individual SNP testing has generally been eclipsed by the greatly more efficient enriched technology utilized with Big Y testing.

Think of SNP testing as walking up to a specific location and taking a look, while NGS scan technology is a drone flying over the entire region 30-50 times looking multiple times to be sure they see the more distant target accurately.

Multiple scans acquiring the same read in the same location, shown below in the Big Y browser tool by the pink mutations at the red arrow, confirm that NGS sequencing is quite reliable.

McNiel Big Y browser

These two types of tests, STR panels 12-111 and the SNP-based Big Y, are meant to be utilized in combination with each other.

STR markers tend to mutate faster and are less reliable, experiencing frustrating back mutations. SNPs very rarely experience this level of instability. Some regions of the Y chromosome are messier or more complicated than others, causing problems with interpreting reads reliably.

For purposes of clarity, the string of pink A reads above is “not messy,” and “A” is very clearly a mutation because all ~39 scanned reads report the same value of “A,” and according to the legend, all of those scans are high quality. Multiple combined reads of A and G, for example, in the same location, would be tough to call accurately and would be considered unreliable.

You can see examples of a few scattered pink misreads, above.

The two different kinds of tests produce results for overlapping timeframes – with STR mutations generally sifting through closer relationships and SNPs reaching back further in time.

Many more men have taken the Y DNA STR tests over the last 20 years. The Big Y tests have only been available for the past handful of years.

STR testing produces the following matches for my McNiel cousin:

STR Level STR Matches STR Matches Who Took the Big Y % STR Who Took Big Y STR Matches Who Also Match on the Big Y
12 5988 796 13 52
25 6660 725 11 57
37 878 94 11 12
67 1225 252 21 23
111 4 2 50 1

Typically, one would expect that all STR matches that took the Big Y would match on the Big Y, since STR results suggest relationships closer in time, but that’s not the case.

  • Many STR testers who have taken the Big Y seem to be just slightly too distant to be considered a Big Y match using SNPs, which flies in the face of conventional wisdom.
  • However, this could easily be a function of the fact that STRs mutate both backward and forwards and may have simply “happened” to have mutated to a common value – which suggests a closer relationship than actually exists.
  • It could also be that the SNP matching threshold needs to be raised since the enhanced and enriched Big Y-700 technology now finds more mutations than the older Big Y-500. I would like to see SNP matching expanded to 40 from 30 because it seems that clan connections may be being missed. Thirty may have been a great threshold before the more sensitive Big Y-700 test revealed more mutations, which means that people hit that 30 threshold before they did with previous tests.
  • Between the combination of STRs and SNPs mutating at the same time, some Big Y matches are pushed just out of range.

In a nutshell, the correlation I expected to find in terms of matching between STR and Big Y testing is not what I found. Let’s take a look at what we discovered.

It’s worth noting that the analysis is easier if you are working together with at least your closest matches or have access via projects to at least some of their results. You can see common STR values to 111 in projects, such as surname projects. Project administrators can view more if project members have allowed access.

Unexpected Discoveries and Gotchas

While I did expect STR matches to also match on the Big Y, I don’t expect the Big Y matches to necessarily match on the STR tests. After all, the Big Y is testing for more deep-rooted history.

Only one of the McNiel Big Y matches also matches at all levels of STR testing. That’s not surprising since Big Y matching reaches further back in time than STR testing, and indeed, not all STR testers have taken a Big Y test.

Of my McNeill cousin’s closest Big Y matches, we find the following relative to STR matching.

Surname Ancestral Location Big Y Variant/SNP Difference STR Match Level
Scott 1565 in Buccleuch, Selkirkshire, Scotland 20 12, 25, 37, 67
McCollum Not listed 21 67 only
Glass 1618 in Banbridge, County Down, Ireland 23 12, 25, 67
McMichael 1720 County Antrim, Ireland 28 67 only
Murphy Not listed 29 12, 25, 37, 67
Campbell Scotland 30 12, 25, 37, 67, 111

It’s ironic that the man who matches on all STR levels has the most variants, 30 – so many that with 1 more, he would not have been considered a Big Y match at all.

Only the Campbell man matches on all STR panels. Unfortunately, this Campbell male does not match the Clan Campbell line, so that momentary clan connection theory is immediately put to rest.

Block Tree Matches – What They Do, and Don’t, Mean

Note that a Carnes male, the other person who matches my McNeill cousin at 111 STR markers and has taken a Big Y test does not match at the Big Y level. His haplogroup BY69003 is located several branches up the tree, with our common ancestor, R-S588, having lived about 2000 years ago. Interestingly, we do match other R-S588 men.

This is an example where the total number of SNP mutations is greater than 30 for these 2 men (McNeill and Carnes), but not for my McNeill cousin compared with other men on the same S588 branch.

McNiel Big Y BY69003

By searching for Carnes on the block tree, I can view my cousin’s match to Mr. Carnes, even though they don’t match on the Big Y. STR matches who have taken the Big Y test, even if they don’t match at the Big Y level, are shown on the Block Tree on their branch.

By clicking on the haplogroup name, R-BY69003, above, I can then see three categories of information about the matches at that haplogroup level, below.

McNiel Big Y STR differences

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By selecting “Matches,” I can see results under the column, “Big Y.” This does NOT mean that the tester matches either Mr. Carnes or Mr. Riker on the Big Y, but is telling me that there are 14 differences out of 615 STR markers above 111 markers for Mr. Carnes, and 8 of 389 for Mr. Riker.

In other words, this Big Y column is providing STR information, not indicating a Big Y match. You can’t tell one way or another if someone shown on the Block Tree is shown there because they are a Big Y match or because they are an STR match that shares the same haplogroup.

As a cautionary note, your STR matches that have taken the Big Y ARE shown on the block tree, which is a good thing. Just don’t assume that means they are Big Y matches.

The 30 SNP threshold precludes some matches.

My research indicates that the people who match on STRs and carry the same haplogroup, but don’t match at the Big Y level, are every bit as relevant as those who do match on the Big Y.

McNIel Big Y block tree menu

If you’re not vigilant when viewing the block tree, you’ll make the assumption that you match all of the people showing on the Block Tree on the Big Y test since Block Tree appears under the Big Y tools. You have to check Big Y matches specifically to see if you match people shown on the Block Tree. You don’t necessarily match all of them on the Big Y test, and vice versa, of course.

You match Block Tree inhabitants either:

  • On the Big Y, but not the STR panels
  • On the Big Y AND at least one level of STRs between 12 and 111, inclusive
  • On STRs to someone who has taken the Big Y test, but whom you do not match on the Big Y test

Big Y-500 or Big Y-700?

McNiel Big Y STR differences

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Looking at the number of STR markers on the matches page of the Block Tree for BY69003, above, or on the STR Matches page is the only way to determine whether or not your match took the Big Y-700 or the Big Y-500 test.

If you add 111 to the Big Y SNP number of 615 for Mr. Carnes, the total equals 726, which is more than 700, so you know he took the Big Y-700.

If you add 111 to 389 for Mr. Riker, you get 500, which is less than 700, so you know that he took the Big Y-500 and not the Big Y-700.

There are still a very small number of men in the database who did not upgrade to 111 when they ordered their original Big Y test, but generally, this calculation methodology will work. Today, all Big Y tests are upgraded to 111 markers if they have not already tested at that level.

Why does Big Y-500 vs Big Y-700 matter? The enriched chemistry behind the testing technology improved significantly with the Big Y-700 test, enhancing Y-DNA results. I was an avowed skeptic until I saw the results myself after upgrading men in the Estes DNA project. In other words, if Big Y-500 testers upgrade, they will probably have more SNPs in common.

You may want to contact your closest Big Y-500 matches and ask if they will consider upgrading to the Big Y-700 test. For example, if we had close McNiel or similar surname matches, I would do exactly that.

Matching Both the Big Y and STRs – No Single Source

There is no single place or option to view whether or not you match someone BOTH on the Big Y AND STR markers. You can see both match categories individually, of course, but not together.

You can determine if your STR matches took the Big Y, below, and their haplogroup, which is quite useful, but you can’t tell if you match them at the Big Y level on this page.

McNiel Big Y STR match Big Y

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Selecting “Display Only Matches With Big Y” means displaying matches to men who took the Big Y test, not necessarily men you match on the Big Y. Mr. Conley, in the example above, does not match my McNeill cousin on the Big Y but does match him at 12 and 25 STR markers.

I hope FTDNA will add three display options:

  • Select only men that match on the Big Y in the STR panel
  • Add an option for Big Y on the advanced matches page
  • Indicate men who also match on STRs on the Big Y match page

It was cumbersome and frustrating to have to view all of the matches multiple times to compile various pieces of information in a separate spreadsheet.

No Big Y Match Download

There is also no option to download your Big Y matches. With a few matches, this doesn’t matter, but with 119 matches, or more, it does. As more people test, everyone will have more matches. That’s what we all want!

What you can do, however, is to download your STR matches from your match page at levels 12-111 individually, then combine them into one spreadsheet. (It would be nice to be able to download them all at once.)

McNiel Big Y csv

You can then add your Big Y matches manually to the STR spreadsheet, or you can simply create a separate Big Y spreadsheet. That’s what I chose to do after downloading my cousin’s 14,737 rows of STR matches. I told you that R-M222 was prolific! I wasn’t kidding.

This high number of STR matches also perfectly illustrates why the Big Y SNP results were so critical in establishing the backbone relationship structure. Using the two tools together is indispensable.

An additional benefit to downloading STR results is that you can sort the STR spreadsheet columns in surname order. This facilitates easily spotting all spelling variations of McNiel, including words like Niel, Neal and such that might be relevant but that you might not notice otherwise.

Creating a Big Y Spreadsheet

My McNiel cousin has 119 Big Y-700 matches.

I built a spreadsheet with the following columns facilitating sorting in a number of ways, with definitions as follows:

McNiel Big Y spreadsheet

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  • First Name
  • Last Name – You will want to search matches on your personal page at Family Tree DNA by this surname later, so be sure if there is a hyphenated name to enter it completely.
  • Haplogroup – You’ll want to sort by this field.
  • Convergent – A field you’ll complete when doing your analysis. Convergence is the common haplogroup in the tree shared by you and your match. In the case of the green matches above, which are color-coded on my spreadsheet to indicate the closest matches with my McNiel cousin, the convergent haplogroup is BY18350.
  • Common Tree Gen – This column is the generations on the Block Tree shown to this common haplogroup. In the example above, it’s between 9 and 14 SNP generations. I’ll show you where to gather this information.
  • Geographic Location – Can be garnered from 4 sources. No color in that cell indicates that this information came from the Earliest Known Ancestor (EKA) field in the STR matches. Blue indicates that I opened the tree and pulled the location information from that source. Orange means that someone else by the same surname whom the tester also Y DNA matches shows this location. I am very cautious when assigning orange, and it’s risky because it may not be accurate. A fourth source is to use Ancestry, MyHeritage, or another genealogical resource to identify a location if an individual provides genealogical information but no location in the EKA field. Utilizing genealogy databases is only possible if enough information is provided to make a unique identification. John Smith 1700-1750 won’t do it, but Seamus McDougal (1750-1810) married to Nelly Anderson might just work.
  • STR Match – Tells me if the Big Y match also matches on STR markers, and if so, which ones. Only the first 111 markers are used for matching. No STR match generally means the match is further back in time, but there are no hard and fast rules.
  • Big Y Match – My original goal was to combine this information with the STR match spreadsheet. If you don’t wish to combine the two, then you don’t need this column.
  • Tree – An easy way for me to keep track of which matches do and do not have a tree. Please upload or create a tree.

You can also add a spreadsheet column for comments or contact information.

McNiel Big Y profile

You will also want to click your match’s name to display their profile card, paying particular attention to the “About Me” information where people sometimes enter genealogical information. Also, scan the Ancestral Surnames where the match may enter a location for a specific surname.

Private Variants

I added additional spreadsheet columns, not shown above, for Private Variant analysis. That level of analysis is beyond what most people are interested in doing, so I’m only briefly discussing this aspect. You may want to read along, so you at least understand what you are looking at.

Clicking on Private Variants in your Big Y Results shows your variants, or mutations, that are unnamed as SNPs. When they are named, they become SNPs and are placed on the haplotree.

The reference or “normal” state for the DNA allele at that location is shown as the “Reference,” and “Genotype” is the result of the tester. Reference results are not shown for each tester, because the majority are the same. Only mutations are shown.

McNiel Big Y private variants

There are 5 Private Variants, total, for my cousin. I’ve obscured the actual variant numbers and instead typed in 111111 and 222222 for the first two as examples.

McNiel Big Y nonmatching variants

In our example, there are 6 Big Y matches, with matches one and five having the non-matching variants shown above.

Non-matching variants mean that the match, Mr. Scott, in example 1, does NOT match the tester (my cousin) on those variants.

  • If the tester (you) has no mutation, you won’t have a Private Variant shown on your Private Variant page.
  • If the tester does have a Private Variant shown, and that variant shows ON their matches list of non-matching variants, it means the match does NOT match the tester, and either has the normal reference value or a different mutation. Explained another way, if you have a mutation, and that variant is listed on your match list of Non-Matching Variants, your match does NOT match you and does NOT have the same mutation.
  • If the match does NOT have the Private Variant on their list, that means the match DOES match the tester, and they both have the same mutation, making this Private Variant a candidate to be named as a new SNP.
  • If you don’t have a Private Variant listed, but it shows in the Non-Matching Variants of your match, that means you have the reference or normal value, and they have a mutation.

In example #1, above, the tester has a mutation at variant 111111, and 111111 is shown as a Non-Matching Variant to Mr. Scott, so Mr. Scott does NOT match the tester. Mr. Scott also does NOT match the tester at locations 222222 and 444444.

In example #5, 111111 is NOT shown on the Non-Matching Variant list, so Mr. Treacy DOES match the tester.

I have a terrible time wrapping my head around the double negatives, so it’s critical that I make charts.

On the chart below, I’ve listed the tester’s private variants in an individual column each, so 111111, 222222, etc.

For each match, I’ve copy and pasted their Non-Matching Variants in a column to the right of the tester’s variants, in the lavender region. In this example, I’ve typed the example variants into separate columns for each tester so you can see the difference. Remember, a non-matching variant means they do NOT match the tester’s mutation.

McNiel private variants spreadsheet

On my normal spreadsheet where the non-matching variants don’t have individuals columns, I then search for the first variant, 111111. If the variant does appear in the list, it means that match #1 does NOT have the mutation, so I DON’T put an X in the box for match #1 under 111111.

In the example above, the only match that does NOT have 111111 on their list of Non-Matching Variants is #5, so an X IS placed in that corresponding cell. I’ve highlighted that column in yellow to indicate this is a candidate for a new SNP.

You can see that no one else has the variant, 222222, so it truly is totally private. It’s not highlighted in yellow because it’s not a candidate to be a new SNP.

Everyone shares mutation 333333, so it’s a great candidate to become a new SNP, as is 555555.

Match #6 shares the mutation at 444444, but no one else does.

This is a manual illustration of an automated process that occurs at Family Tree DNA. After Big Y matches are returned, automated software creates private variant lists of potential new haplogroups that are then reviewed internally where SNPs are evaluated, named, and placed on the tree if appropriate.

If you follow this process and discover matches, you probably don’t need to do anything, as the automated review process will likely catch up within a few days to weeks.

Big Y Matches

In the case of the McNiel line, it was exciting to discover several private variants, mutations that were not yet named SNPs, found in several matches that were candidates to be named as SNPs and placed on the Y haplotree.

Sure enough, a few days later, my McNeill cousin had a new haplogroup assignment.

Most people have at least one Private Variant, locations in which they do NOT match another tester. When several people have these same mutations, and they are high-quality reads, the Private Variant qualifies to be added to the haplotree as a SNP, a task performed at FamilyTreeDNA by Michael Sager.

If you ever have the opportunity to hear Michael speak, please do so. You can watch Michael’s presentation at Genetic Genealogy Ireland (GGI) titled “The Tree of Mankind,” on YouTube, here, compliments of Maurice Gleeson who coordinates GGI. Maurice has also written about the Gleeson Y DNA project analysis, here.

As a result of Cousin McNeill’s test, six new SNPs have been added to the Y haplotree, the tree of mankind. You can see our new haplogroup for our branch, BY18332, with an equivalent SNP, BY25938, along with three sibling branches to the left and right on the tree.

McNiel Big Y block tree 4 branch

Big Y testing not only answers genealogical questions, it advances science by building out the tree of mankind too.

The surname of the men who share the same haplogroup, R-BY18332, meaning the named SNP furthest down the tree, are McCollum and Campbell. Not what I expected. I expected to find a McNeil who does match on at least some STR markers. This is exactly why the Big Y is so critical to define the tree structure, then use STR matches to flesh it out.

Taking the Big Y-700 test provided granularity between 6 matches, shown above, who were all initially assigned to the same branch of the tree, BY18350, but were subsequently divided into 4 separate branches. My McNiel cousin is no longer equally as distant from all 6 men. We now know that our McNiel line is genetically closer on the Y chromosome to Campbell and McCollum and further distant from Murphy, Scott, McMichael, and Glass.

Not All SNP Matches are STR Matches

Not all SNP matches are also STR matches. Some relationships are too far back in time. However, in this case, while each person on the BY18350 branches matches at some STR level, only the Campbell individual matches at all STR levels.

Remember that variants (mutations) are accumulating down both respective branches of the tree at the same time, meaning one per roughly every 100 years (if 100 is the average number we want to use) for both testers. A total of 30 variants or mutations difference, an average of 15 on each branch of the tree (McNiel and their match) would suggest a common ancestor about 1500 years ago, so each Big Y match should have a common ancestor 1500 years ago or closer. At least on average, in theory.

The Big Y test match threshold is 30 variants, so if there were any more mismatches with the Campbell male, they would not have been a Big Y match, even though they have the exact same haplogroup.

Having the same haplogroup means that their terminal SNP is identical, the SNP furthest down the tree today, at least until someone matches one of them on their Private Variants (if any remain unnamed) and a new terminal SNP is assigned to one or both of them.

Mutations, and when they happen, are truly a roll of the dice. This is why viewing all of your Big Y Block Tree matches is critical, even if they don’t show on your Big Y match list. One more variant and Campbell would have not been shown as a match, yet he is actually quite close, on the same branch, and matches on all STR panels as well.

SNPs Establish the Backbone Structure

I always view the block tree first to provide a branching tree structure, then incorporate STR matches into the equation. Both can equally as important to genealogy, but haplogroup assignment is the most accurate tool, regardless of whether the two individuals match on the Big Y test, especially if the haplogroups are relatively close.

Let’s work with the Block Tree.

The Block Tree

McNIel Big Y block tree menu

Clicking on the link to the Block Tree in the Big Y results immediately displays the tester’s branch on the tree, below.

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On the left side are SNP generation markers. Keep in mind that approximate SNP generations are marked every 5 generations. The most recent generations are based on the number of private variants that have not yet been assigned as branches on the tree. It’s possible that when they are assigned that they will be placed upstream someplace, meaning that placement will reduce the number of early branches and perhaps increase the number of older branches.

The common haplogroup of all of the branches shown here with the upper red arrow is R-BY3344, about 15 SNP generations ago. If you’re using 100 years per SNP generation, that’s about 1500 years. If you’re using 80 years, then 1200 years ago. Some people use even fewer years for calculations.

If some of the private variants in the closer branches disappear, then the common ancestral branch may shift to closer in time.

This tree will always be approximate because some branches can never be detected. They have disappeared entirely over time when no males exist to reproduce.

Conversely, subclades have been born since a common ancestor clade whose descendants haven’t yet tested. As more people test, more clades will be discovered.

Therefore, most recent common ancestor (MRCA) haplogroup ages can only be estimated, based on who has tested and what we know today. The tree branches also vary depending on whether testers have taken the Big Y-500 or the more sensitive Big Y-700, which detects more variants. The Y haplotree is a combination of both.

Big Y-500 results will not be as granular and potentially do not position test-takers as far down the tree as Big Y-700 results would if they upgraded. You’ll need to factor that into your analysis if you’re drawing genealogical conclusions based on these results, especially close results.

You’ll note that the direct path of descent is shown above with arrows from BY3344 through the first blue box with 5 equivalent SNPS, to the next white box, our branch, with two equivalent SNPs. Our McNeil ancestor, the McCollum tester, and the Campell tester have no unresolved private variants between them, which suggests they are probably closer in time than 10 generations back. You can see that the SNP generations are pushed “up” by the neighbor variants.

Because of the fact that private variants don’t occur on a clock cycle and occur in individual lines at an unsteady rate, we must use averages.

That means that when we look further “up” the tree, clicking generation by generation on the up arrow above BY3344, the SNP generations on the left side “adjust” based on what is beneath, and unseen at that level.

The Block Tree Adjusts

Note, in the example above, BY3344 is at SNP generation 15.

Next, I clicked one generation upstream, to R-S668.

McNiel Big Y block tree S668

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You can see that S668 is about 21 SNP generations upstream, and now BY3344 is listed as 20 generations, not 15. You can see our branch, BY3344, but you can no longer see subclades or our matches below that branch in this view.

You can, however, see two matches that descend through S668, brother branches to BY3344, red arrows at far right.

Clicking on the up arrow one more time shows us haplogroup S673, below, and the child branches. The three child branches on which the tester has matches are shown with red arrows.

McNiel Big Y S673

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You’ll immediately notice that now S668 is shown at 19 SNP generations, not 20, and S673 is shown at 20. This SNP generation difference between views is a function of dealing with aggregated and averaged private variants on combined lines and causes the SNP generations to shift. This is also why I always say “about.”

As you continue to click up the tree, the shifting SNP generations continue, reminding us that we can’t truly see back in time. We can only achieve approximations, but those approximations improve as more people test, and more SNPs are named and placed in their proper places on the phylotree.

I love the Block Tree, although I wish I could see further side-to-side, allowing me to view all of the matches on one expanded tree so I can easily see their relationships to the tester, and each other.

Countries and Origins

In addition to displaying shared averaged autosomal origins of testers on a particular branch, if they have taken the Family Finder test and opted-in to sharing origins (ethnicity) results, you can also view the countries indicated by testers on that branch along with downstream branches of the tree.

McNiel Big Y countries

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For example, the Countries tab for S673 is shown above. I can see matches on this branch with no downstream haplogroup currently assigned, as well as cumulative results from downstream branches.

Still, I need to be able to view this information in a more linear format.

The Block Tree and spreadsheet information beautifully augment the haplotree, so let’s take a look.

The Haplotree

On your Y DNA results page, click on the “Haplotree and SNPs” link.

McNIel Big Y haplotree menu

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The Y haplotree will be displayed in pedigree style, quite familiar to genealogists. The SNP legend will be shown at the top of the display. In some cases, “presumed positive” results occur where coverage is lacking, back mutations or read errors are encountered. Presumed positive is based on positive SNPs further down the tree. In other words, that yellow SNP below must read positive or downstream ones wouldn’t.

McNIel Big Y pedigree descent

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The tester’s branch is shown with the grey bar. To the right of the haplogroup-defining SNP are listed the branch and equivalent SNP names. At far right, we see the total equivalent SNPs along with three dots that display the Country Report. I wish the haplotree also showed my matches, or at least my matching surnames, allowing me to click through. It doesn’t, so I have to return to the Big Y page or STR Matches page, or both.

I’ve starred each branch through which my McNiell cousin descends. Sibling branches are shown in grey. As you’ll recall from the Block Tree, we do have matches on those sibling branches, shown side by side with our branch.

The small numbers to the right of the haplogroup names indicate the number of downstream branches. BY18350 has three, all displayed. But looking upstream a bit, we see that DF97 has 135 downstream branches. We also have matches on several of those branches. To show those branches, simply click on the haplogroup.

The challenge for me, with 119 McNeill matches, is that I want to see a combination of the block tree, my spreadsheet information, and the haplotree. The block tree shows the names, my spreadsheet tells me on which branches to look for those matches. Many aren’t easily visible on the block tree because they are downstream on sibling branches.

Here’s where you can find and view different pieces of information.

Data and Sources STR Matches Page Big Y Matches Page Block Tree Haplogroups & SNPs Page
STR matches Yes No, but would like to see who matches at which STR levels If they have taken Big Y test, but doesn’t mean they match on Big Y matching No
SNP matches *1 Shows if STR match has common haplogroup, but not if tester matches on Big Y No, but would like to see who matches at which STR level Big Y matches and STR matches that aren’t Big Y matches are both shown No, but need this feature – see combined haplotree/ block tree
Other Haplogroup Branch Residents Yes, both estimated and tested No, use block tree or click through to profile card, would like to see haplogroup listed for Big Y matches Yes, both Big Y and STR tested, not estimated. Cannot tell if person is Big Y match or STR match, or both. No individuals, but would like that as part of countries report, see combined haplotree/block tree
Fully Expanded Phylotree No No Would like ability to see all branches with whom any Big Y or STR match resides at one time, even if it requires scrolling Yes, but no match information. Matches report could be added like on Block Tree.
Averaged Ethnicities if Have FF Test No No Yes, by haplogroup branch No
Countries Matches map STR only No, need Big Y matches map Yes Yes
Earliest Known Ancestor Yes No, but can click through to profile card No No
Customer Trees Yes No, need this link No No
Profile Card Yes, click through Yes, click through Yes, click through No match info on this page
Downloadable data By STR panel only, would like complete download with 1 click, also if Big Y or FF match Not available at all No No
Path to common haplogroup No No, but would like to see matches haplogroup and convergent haplogroup displayed No, would like the path to convergent haplogroup displayed as an option No, see combined match-block -haplotree in next section

*1 – the best way to see the haplogroup of a Big Y match is to click on their name to view their profile card since haplogroup is not displayed on the Big Y match page. If you happen to also match on STRs, their haplogroup is shown there as well. You can also search for their name using the block tree search function to view their haplogroup.

Necessity being the mother of invention, I created a combined match/block tree/haplotree.

And I really, REALLY hope Family Tree DNA implements something like this because, trust me, this was NOT fun! However, now that it’s done, it is extremely useful. With fewer matches, it should be a breeze.

Here are the steps to create the combined reference tree.

Combo Match/Block/Haplotree

I used Snagit to grab screenshots of the various portions of the haplotree and typed the surnames of the matches in the location of our common convergent haplogroup, taken from the spreadsheet. I also added the SNP generations in red for that haplogroup, at far left, to get some idea of when that common ancestor occurred.

McNIel Big Y combo tree

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This is, in essence, the end-goal of this exercise. There are a few steps to gather data.

Following the path of two matches (the tester and a specific match) you can find their common haplogroup. If your match is shown on the block tree in the same view with your branch, it’s easy to see your common convergent parent haplogroup. If you can’t see the common haplogroup, it’s takes a few extra steps by clicking up the block tree, as illustrated in an earlier section.

We need the ability to click on a match and have a tree display showing both paths to the common haplogroup.

McNiel Big Y convergent

I simulated this functionality in a spreadsheet with my McNiel cousin, a Riley match, and an Ocain match whose terminal SNP is the convergent SNP (M222) between Riley and McNiel. Of course, I’d also like to be able to click to see everyone on one chart on their appropriate branches.

Combining this information onto the haplotree, in the first image, below, M222, 4 men match my McNeill cousin – 2 who show M222 as their terminal SNP, and 2 downstream of M222 on a divergent branch that isn’t our direct branch. In other words, M222 is the convergence point for all 4 men plus my McNeill cousin.

McNiel Big Y M222 haplotree

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In the graphic below, you can see that M222 has a very large number of equivalent SNPs, which will likely become downstream haplogroups at some point in the future. However, today, these equivalent SNPs push M222 from 25 generations to 59. We’ll discuss how this meshes with known history in a minute.

McNiel Big Y M222 block tree

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Two men, Ocain and Ransom, who have both taken the Big Y, whose terminal SNP is M222, match my McNiel cousin. If their common ancestor was actually 59 generations in the past, it’s very, very unlikely that they would match at all given the 30 mutation threshold.

On my reconstructed Match/Block/Haplotree, I included the estimated SNP generations as well. We are starting with the most distant haplogroups and working our way forward in time with the graphics, below.

Make no mistake, there are thousands more men who descend from M222 that have tested, but all of those men except 4 have more than 30 mutations total, so they are not shown as Big Y matches, and they are not shown individually on the Block Tree because they neither match on the Big Y or STR tests. However, there is a way to view information for non-matching men who test positive for M222.

McNiel Big Y M222 countries

click to enlarge

Looking at the Block Tree for M222, many STR match men took a SNP test only to confirm M222, so they would be shown positive for the M222 SNP on STR results and, therefore, in the detailed view of M222 on the Block tree.

Haplogroup information about men who took the M222 test and whom the tester doesn’t match at all are shown here as well in the country and branch totals for R-M222. Their names aren’t displayed because they don’t match the tester on either type of Y DNA test.

Back to constructing my combined tree, I’ve left S658 in both images, above and below, as an overlap placeholder, as we move further down, or towards current, on the haplotree.

McNiel Big Y combo tree center

click to enlarge

Note that BY18350, above, is also an overlap connecting below.

You’ll recall that as a result of the Big Y test, BY18350 was split and now has three child branches plus one person whose terminal SNP is BY18350. All of the men shown below were on one branch until Big Y results revealed that BY18350 needed to be split, with multiple new haplogroups added to the tree.

McNiel Big Y combo tree current

click to enlarge

Using this combination of tools, it’s straightforward for me to see now that our McNiel line is closest to the Campbell tester from Scotland according to the Big Y test + STRs.

Equal according to the Big Y test, but slightly more distant, according to STR matching, is McCollum. The next closest would be sibling branches. Then in the parent group of the other three, BY18350, we find Glass from Scotland.

In BY18350 and subgroups, we find several Scotland locations and one Northern Ireland, which was likely from Scotland initially, given the surname and Ulster Plantation era.

The next upstream parent haplogroup is BY3344, which looks to be weighted towards ancestors from Scotland, shown on the country card, below.

McNiel Big Y BY3344

click to enlarge

This suggests that the origins of the McNiel line was, perhaps, in Scotland, but it doesn’t tell us whether or not George and presumably, Thomas, immigrated from Ireland or Scotland.

This combined tree, with SNPs, surnames from Big Y matches, along with Country information, allows me to see who is really more closely related and who is further away.

What I didn’t do, and probably should, is to add in all of the STR matches who have taken the Big Y test, shown on their convergent branch – but that’s just beyond the scope of time I’m willing to invest, at least for now, given that hundreds of STR matches have taken the Big Y test, and the work of building the combined tree is all manual today.

For those reading this article without access to the Y phylogenetic tree, there’s a public version of the Y and mitochondrial phylotrees available, here.

What About Those McNiels?

No other known McNiel descendants from either Thomas or George have taken the Big Y test, so I didn’t expect any to match, but I am interested in other men by similar surnames. Does ANY other McNiel have a Big Y match?

As it turns out, there are two, plus one STR match who took a Big Y test, but is not a Big Y match.

However, as you can see on the combined match/block/haplotree, above, the closest other Big Y-matching McNeil male is found at about 19 SNP generations, or roughly 1900 years ago. Even if you remove some of the variants in the lower generations that are based on an average number of individual variants, you’re still about 1200 years in the past. It’s extremely doubtful that any surname would survive in both lines from the year 800 or so.

That McNeil tester’s ancestor was born in 1747 in Tranent, Scotland.

The second Big Y-matching person is an O’Neil, a few branches further up in the tree.

The convergent SNP of the two branches, meaning O’Neil and McNeill are at approximately the 21 generation level. The O’Neil man’s Neill ancestor is found in 1843 in Cookestown, County Tyrone, Ireland.

McNiel Big Y convergent McNeil lines

I created a spreadsheet showing convergent lines:

  • The McNeill man with haplogroup A4697 (ancestor Tranent, Scotland) is clearly closest genetically.
  • O’Neill BY91591, who is brother clades with Neel and Neal, all Irish, is another Big Y match.
  • The McNeill man with haplogroup FT91182 is an STR match, but not a Big Y match.

The convergent haplogroup of all of these men is DF105 at about the 22 SNP generation marker.


Let’s turn back to STR tests, with results that produce matches closer in time.

Searching my STR download spreadsheet for similar surnames, I discovered several surname matches, mining the Earliest Known Ancestor information, profiles and trees produced data as follows:

Ancestor STR Match Level Location
George Charles Neil 12, 25, match on Big Y A4697 1747-1814 Tranent, Scotland
Hugh McNeil 25 (tested at 67) Born 1800 Country Antrim, Northern Ireland
Duncan McNeill 12 (tested at 111) Married 1789, Argyllshire, Scotland
William McNeill 12, 25 (tested at 37) Blackbraes, Stirlingshire, Scotland
William McNiel 25 (tested at 67) Born 1832 Scotland
Patrick McNiel 25 (tested at 111) Trien East, County Roscommon, Ireland
Daniel McNeill 25 (tested at 67) Born 1764 Londonderry, Northern Ireland
McNeil 12 (tested at 67) 1800 Ireland
McNeill (2 matches) 25 (tested Big Y-  SNP FT91182) 1810, Antrim, Northern Ireland
Neal 25 – (tested Big Y, SNP BY146184) Antrim, Northern Ireland
Neel (2 matches) 67 (tested at 111, and Big Y) 1750 Ireland, Northern Ireland

Our best clue that includes a Big Y and STR match is a descendant of George Charles Neil born in Tranent, Scotland, in 1747.

Perhaps our second-best clue comes in the form of a 111 marker match to a descendant of one Thomas McNeil who appears in records as early as 1753 and died in 1761 In Rombout Precinct, Dutchess County, NY where his son John was born. This line and another match at a lower level both reportedly track back to early New Hampshire in the 1600s.

The MacNeil DNA Project tells us the following:

Participant 106370 descends from Isaiah McNeil b. 14 May 1786 Schaghticoke, Rensselaer Co. NY and d. 28 Aug 1855 Poughkeepsie, Dutchess Co., NY, who married Alida VanSchoonhoven.

Isaiah’s parents were John McNeal, baptized 21 Jun 1761 Rombout, Dutchess Co., NY, d. 15 Feb 1820 Stillwater, Saratoga Co., NY and Helena Van De Bogart.

John’s parents were Thomas McNeal, b.c. 1725, d. 14 Aug 1761 NY and Rachel Haff.

Thomas’s parents were John McNeal Jr., b. around 1700, d. 1762 Wallkill, Orange Co., NY (now Ulster Co. formed 1683) and Martha Borland.

John’s parents were John McNeal Sr. and ? From. It appears that John Sr. and his family were this participant’s first generation of Americans.

Searching this line on Ancestry, I discovered additional information that, if accurate, may be relevant. This lineage, if correct, and it may not be, possibly reaching back to Edinburgh, Scotland. While the information gathered from Ancestry trees is certainly not compelling in and of itself, it provides a place to begin research.

Unfortunately, based on matches shown on the MacNeil DNA Project public page, STR marker mutations for kits 30279, B78471 and 417040 when compared to others don’t aid in clustering or indicating which men might be related to this group more closely than others using line-marker mutations.

Matches Map

Let’s take a look at what the STR Matches Map tells us.

McNiel Big Y matches map menu

This 67 marker Matches Map shows the locations of the earliest known ancestors of STR matches who have entered location information.

McNiel Big Y matches mapMcNiel Big Y matches map legend

My McNeill cousin’s closest matches are scattered with no clear cluster pattern.

Unfortunately, there is no corresponding map for Big Y matches.


The SNP map provided under the Y DNA results allows testers to view the locations where specific haplogroups are found.

McNiel Big Y SNP map

The SNP map marks an area where at least two or more people have claimed their most distant known ancestor to be. The cluster size is the maximum amount of miles between people that is allowed in order for a marker indicating a cluster at a location to appear. So for example, the sample size is at least 2 people who have tested, and listed their most distant known ancestor, the cluster is the radius those two people can be found in. So, if you have 10 red dots, that means in 1000 miles there are 10 clusters of at least two people for that particular SNP. Note that these locations do NOT include people who have tested positive for downstream locations, although it does include people who have taken individual SNP tests.

Working my way from the McNiel haplogroup backward in time on the SNP map, neither BY18332 nor BY18350 have enough people who’ve tested, or they didn’t provide a location.

Moving to the next haplogroup up the tree, two clusters are formed for BY3344, shown below.

McNIel Big Y BY3344 map

S668, below.

McNiel Big Y S668 map

It’s interesting that one cluster includes Glasgow.

S673, below.

McNiel Big Y S673 map

DF85, below:

McNiel Big Y DF85 map

DF105 below:

McNiel BIg Y DF105 map

M222, below:

McNiel Big Y M222 map

For R-M222, I’ve cropped the locations beyond Ireland and Scotland. Clearly, RM222 is the most prevalent in Ireland, followed by Scotland. Wherever M222 originated, it has saturated Ireland and spread widely in Scotland as well.


R-M222, the SNP initially thought to indicate Niall of the 9 Hostages, occurred roughly 25-59 SNP generations in the past. If this age is even remotely accurate, averaging by 80 years per generation often utilized for Big Y results, produces an age of 2000 – 4720 years. I find it extremely difficult to believe any semblance of a surname survived that long. Even if you reduce the time in the past to the historical narrative, roughly the year 400, 1600 years, I still have a difficult time believing the McNiel surname is a result of being a descendant of Niall of the 9 Hostages directly, although oral history does have staying power, especially in a clan setting where clan membership confers an advantage.

Surname or not, clearly, our line along with the others whom we match on the Big Y do descend from a prolific common ancestor. It’s very unlikely that the mutation occurred in Niall’s generation, and much more likely that other men carried M222 and shared a common ancestor with Niall at some point in the distant past.

McNiel Conclusion – Is There One?

If I had two McNiel wishes, they would be:

  • Finding records someplace in Virginia that connect George and presumably brothers Thomas and John to their parents.
  • A McNiel male from wherever our McNiel line originated becoming inspired to Y DNA test. Finding a male from the homeland might point the way to records in which I could potentially find baptismal records for George about 1720 and Thomas about 1724, along with possibly John, if he existed.

I remain hopeful for a McNiel from Edinburgh, or perhaps Glasgow.

I feel reasonably confident that our line originated genetically in Scotland. That likely precludes Niall of the 9 Hostages as a direct ancestor, but perhaps not. Certainly, one of his descendants could have crossed the channel to Scotland. Or, perhaps, our common ancestor is further back in time. Based on the maps, it’s clear that M222 saturates Ireland and is found widely in Scotland as well.

A great deal depends on the actual age of M222 and where it originated. Certainly, Niall had ancestors too, and the Ui Neill dynasty reaches further back, genetically, than their recorded history in Ireland. Given the density of M222 and spread, it’s very likely that M222 did, in fact, originate in Ireland or, alternatively, very early in Scotland and proliferated in Ireland.

If the Ui Neill dynasty was represented in the persona of the High King, Niall of the 9 Hostages, 1600 years ago, his M222 ancestors were clearly inhabiting Ireland earlier.

We may not be descended from Niall personally, but we are assuredly related to him, sharing a common ancestor sometime back in the prehistory of Ireland and Scotland. That man would sire most of the Irish men today and clearly, many Scots as well.

Our ancestors, whoever they were, were indeed in Ireland millennia ago. R-M222, our ancestor, was the ancestor of the Ui Neill dynasty and of our own Reverend George McNiel.

Our ancestors may have been at Knowth and New Grange, and yes, perhaps even at Tara.

Tara Niall mound in sun

Someplace in the mists of history, one man made a different choice, perhaps paddling across the channel, never to return, resulting in M222 descendants being found in Scotland. His descendants include our McNeil ancestors, who still slumber someplace, awaiting discovery.



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DNA Inherited from Grandparents and Great-Grandparents

Philip Gammon, our statistician friend has been working with crossover simulations again in order to tell us what we might expect relative to how much DNA we actually inherit from grandparents and great-grandparents.

We know that on average, we’re going to inherit 25% of our DNA from each grandparent – but we also know in reality that’s not what happens. We get more or less than exactly 25% from each person in a grandparent pair. It’s the total of the DNA of both grandparents that adds up to 50% for the couple.

How does this work, and does it make a difference whether we inherit our grandparent’s DNA through males or females?

Philip has answers for us as a result of his simulations.

DNA Inheritance from Grandparents

Philip Gammon:

When we consider the DNA that we inherit from our ancestors the only quantity that we can be certain of is that we receive half of our autosomal DNA from each parent. This is delivered to us in the form of the 22 segments (i.e. chromosomes) provided by our mothers in the ova and the 22 segments/chromosomes provided by our fathers in the sperm cell. Beyond parent-child relationships we tend to talk about averages. For instance, we receive an average of one quarter of our DNA from each of our four grandparents and an average of one-eighth of our DNA from each of our eight great-grandparents etc.

These figures vary because our parents didn’t necessarily pass on to us equal portions of the DNA that they received from their parents. The level of variation is driven by the number (and location) of crossover events that occur when the ova and the sperm cells are created.

The statistics relevant to the recombination process were discussed in detail in a previous article (Crossovers: Frequency and Inheritance Statistics – Male Versus Female Matters). With the availability these days of abundant real data from direct-to-consumer genetic testing companies (such as the 23andMe data utilised by Campbell et. al. in their paper titled “Escape from crossover interference increases with maternal age”) we can use this information as a basis for simulations that accurately mimic the crossover process. From these simulations we can measure the amount of variation that is expected to be observed in the proportions of DNA inherited from our ancestors. This is precisely what I have done in simulations run on my GAT-C model.

Before looking at the simulation results let’s anticipate what we expect to see. The previous article on crossover statistics revealed that there are an average of about 42 crossovers in female meiosis and about 27 in male meiosis. So, on the set of 22 chromosomes received from our mothers there will have been an average of 42 crossover locations where there was a switch between DNA she inherited from one parent to the other. That means that the DNA we inherit from our maternal grandparents typically comes in about 64 segments, but it won’t necessarily be 32 segments from each maternal grandparent. Chromosomes that experienced an odd number of crossovers contain an even number of segments (half originating from the grandmother, the other half from the grandfather) but chromosomes with an even number of crossovers (or zero!) have an odd number of segments so on these chromosomes you must receive one more segment from one grandparent than the other. And of course not all segments are the same size either. A single crossover occurring close to one end of the chromosome results in a small segment from one grandparent and a large segment from the other. All up there are quite a few sources of variation that can affect the amount of DNA inherited from grandparents. The only certainty here is that the amount inherited from the two maternal grandparents must add to 50%. If you inherit more than the average of 25% from one maternal grandparent that must be offset by inheriting less than 25% from the other maternal grandparent.

Gammon grandparents maternal percent.png

The above chart shows the results of 100,000 simulation runs. Excluding the bottom and top 1% of results, 98% of people will receive between 18.7% and 31.3% of their DNA from a maternal grandparent. The more darkly shaded region in the centre shows the people who receive a fairly even split of between 24% and 26% from the maternal grandparents. Only 28.8% of people are in this region and the remainder receive a less even contribution.

On the set of 22 chromosomes received from fathers there will have been an average of around 27 crossovers so the DNA received from the paternal grandparents has only been split into around 49 segments. It’s the same amount of DNA as received from mothers but just in larger chunks of the grandparent’s DNA. This creates greater opportunity for the father to pass on unequal amounts of DNA from the two grandparents so it would be expected that results from paternal inheritance will show more variation than from maternal inheritance.

Gammon grandparents paternal percent.png

The above chart shows the results of 100,000 simulated paternal inheritance events. They are more spread out than the maternal events with the middle 98% of people receiving between 16.7% and 33.3% of their DNA from a paternal grandparent. Only 21.9% of people receive a fairly even split of between 24% and 26% from each paternal grandparent as shown by the more darkly shaded region in the centre.

Gammon grandparents percent cM.png

To help with the comparison between maternal and paternal inheritance from grandparents the two distributions have been overlayed on the same scale in the chart above. And what are the chances of receiving a fairly even split of grandparents DNA from both your mother and your father? Only 6.3% of people can be expected to inherit an amount of between 24% and 26% of their DNA from all four grandparents.

Now I’ll extend the simulations out to the next generation and examine the variation in proportions of DNA inherited from the eight great-grandparents. There are effectively four groups of great-grandparents:

  • Mother’s maternal grandparents
  • Mother’s paternal grandparents
  • Father’s maternal grandparents
  • Father’s paternal grandparents

The DNA from group 1 has passed to you via two maternal recombination events, from your mother’s mother to your mother, then from your mother to you. On average there would have been 42 crossovers in each of these recombination events. Group 4 comprised two paternal recombination events averaging only 27 crossovers in each. The average amount of DNA received along each path is the same but along the group 1 path it would comprise of more numerous smaller segments than the group 4 path. Groups 2 and 3 would be somewhere between, both consisting of one maternal and one paternal recombination event.

Gammon greatgrandparents percent cM.png

The above chart shows the variation in the amount of DNA received from members of the four groups of great-grandparents. 25,000 simulations were performed. The average amount from any great-grandparent is 12.5% but there can be considerably more variation in the amount received from the father’s paternal grandparents than from the mother’s maternal grandparents. Groups 2 and 3 are between these two extremes and are equivalent. It doesn’t matter whether a paternal recombination follows a maternal one or vice versa – the end result is that both paths consist of the same average number of crossovers.

The table below shows the range in the amount of DNA that people receive from their great-grandparents. The bottom and top 1% of outcomes have been excluded. Note that these are based on a total of 3,418 cM for the 22 autosomes which is the length observed in the Campbell et. al. study. The average of 12.5% of total DNA is 854.5 cM:

Group 1st percentile 99th percentile
Mother’s maternal grandparents 522 cM 1219 cM
Mother’s paternal grandparents 475 cM 1282 cM
Father’s maternal grandparents 475 cM 1281 cM
Father’s paternal grandparents 426 cM 1349 cM

As a matter of interest, in each of the 25,000 simulations the amount of DNA received from the eight great-grandparents were sorted into order from the highest cM to the lowest cM. The averages of each of these eight amounts were then calculated and the results are below:

Gammon greatgrandparents average cM.png

On average, a person receives 1,129 cM from the great-grandparent that they inherited the most of their DNA from and only 600 cM from the great-grandparent that they received the least of their DNA from. But none of us are the result of 25,000 trials – we are each the product of recombination events that occurred once only. The above chart shows the average or typical variation in the amount of DNA received from the eight great-grandparents. Half of people will have experienced more variation than shown above and half of people will have experienced less variation.

Could you have received the same amount of DNA from all eight grandparents? Of course, it is possible, but it turns out that it is extremely unlikely. The average is 12.5% (854.5 cM) so anything between 12% (820.4 cM) and 13% (888.7 cM) could be considered as being close to this figure. The results reveal that this did not occur in any of the 25,000 simulations. Not one person received amounts between 12% and 13% from all eight great-grandparents.

Widening the criteria, I observe that there were 13 instances in the 25,000 simulations where people received between 11.5% and 13.5% of their DNA from all eight great-grandparents. That is still an extremely rare occurrence. Expanding the range further to between 11% and 14% saw a total of 126 instances, but this still only represents about half a percent of all observations. I think that we just have to face the fact that unless we are an extremely rare individual then we will not have inherited close to equal amounts of DNA from our eight great-grandparents.

Now, back to Roberta.

Thanks Philip.

Now we see why we might not inherit the same amount of DNA from our grandparents and great-grandparents.

We Don’t Have Equal Numbers of Matches on Tree Branches

This also might explain, at least in part, why people don’t have the same number of DNA matches on each branch of their tree.

Of course, other reasons include:

  • Uneven family sizes
  • Fewer or more cousins testing on different branches
  • Recent immigration meaning there are few people available to test
  • Family from a region where DNA testing and/or genealogy is not popular
  • Endogamy which dramatically increases the number of people you will match

Real Life Example

In our real-life example, two grandchildren are fortunate to have three grandparents and one great-grandparent available for matching.

For comparison purposes, let’s take a look at how many matches each grandchild has in common with their grandparents and great-grandparent.

The line of descent is as follows:

Gammon line of descent.png

Both end of line testers are female children.

The transmission path from their great-grandmother is:

  • Female to their paternal grandmother
  • Female to their father
  • Male to female tester

The transmission path from their maternal grandfather is:

  • Male to their mother
  • Female to female tester

The transmission path from their maternal grandmother is:

  • Female to their mother
  • Female to female tester

This first chart shows the number of common matches.

Matches Grand 1 Grand 2 GGF GGM Grand 3 Grand 4
Female 1 absent 1061 absent 238 529 1306
Female 2 absent 1225 absent 431 700 1064

It’s interesting that the matches in just 3 generations to the great-grandmother vary by 55%. The second tester has almost twice as many matches in common with her great-great-grandmother as she does the first tester. There a difference in the earlier generation, meaning matches to Grand 2, but only about 23%. That difference increased significantly in one generation.

The second chart shows the total number of matching cM with the matching family member.

Total cM Grand 1 Grand 2 GGF GGM Grand 3 Grand 4
Female 1 absent 1688 absent 713 1601 1818
Female 2 absent 1750 absent 852 1901 1511

We can see that the amount of DNA inherited from a grandparent does correlate with the number of matches to that grandparents. The more DNA shared, of course the better the chances of sharing that DNA with another person. However, multiple factors may be involved with why some people have more or fewer matches.



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Hit a Genetic Genealogy Home Run Using Your Double-Sided Two-Faced Chromosomes While Avoiding Imposters

Do you want to hit a home run with your DNA test, but find yourself a mite bewildered?

Yep, those matches can be somewhat confusing – especially if you don’t understand what’s going on. Do you have a nagging feeling that you might be missing something?

I’m going to explain chromosome matching, and its big sister, triangulation, step by step to remove any confusion, to help you sort through your matches and avoid imposters.

This article is one of the most challenging I’ve ever written – in part because it’s a concept that I’m so familiar with but can be, and is, misinterpreted so easily. I see mistakes and confusion daily, which means that resulting conclusions stand a good chance of being wrong.

I’ve tried to simplify these concepts by giving you easy-to-use memory tools.

There are three key phrases to remember, as memory-joggers when you work through your matches using a chromosome browser: double-sided, two faces and imposter. While these are “cute,” they are also quite useful.

When you’re having a confusing moment, think back to these memory-jogging key words and walk yourself through your matches using these steps.

These three concepts are the foundation of understanding your matches, accurately, as they pertain to your genealogy. Please feel free to share, link or forward this article to your friends and especially your family members (including distant cousins) who work with genetic genealogy. 

Now, it’s time to enjoy your double-sided, two-faced chromosomes and avoid those imposters:)

Are you ready? Grab a nice cup of coffee or tea and learn how to hit home runs!

Double-Sided – Yes, Really

Your chromosomes really are double sided, and two-faced too – and that’s a good thing!

However, it’s initially confusing because when we view our matches in a chromosome browser, it looks like we only have one “bar” or chromosome and our matches from both our maternal and paternal sides are both shown on our one single bar.

How can this be? We all have two copies of chromosome 1, one from each parent.

Chromosome 1 match.png

This is my chromosome 1, with my match showing in blue when compared to my chromosome, in gray, as the background.

However, I don’t know if this blue person matches me on my mother’s or father’s chromosome 1, both of which I inherited. It could be either. Or neither – meaning the dreaded imposter – especially that small blue piece at left.

What you’re seeing above is in essence both “sides” of my chromosome number 1, blended together, in one bar. That’s what I mean by double-sided.

There’s no way to tell which side or match is maternal and which is paternal without additional information – and misunderstanding leads to misinterpreting results.

Let’s straighten this out and talk about what matches do and don’t mean – and why they can be perplexing. Oh, and how to discover those imposters!

Your Three Matches

Let’s say you have three matches.

At Family Tree DNA, the example chromosome browser I’m using, or at any vendor with a chromosome browser, you select your matches which are viewed against your chromosomes. Your chromosomes are always the background, meaning in this case, the grey background.

Chromosome 1-4.png

  • This is NOT three copies each of your chromosomes 1, 2, 3 and 4.
  • This is NOT displaying your maternal and paternal copies of each chromosome pictured.
  • We CANNOT tell anything from this image alone relative to maternal and paternal side matches.
  • This IS showing three individual people matching you on your chromosome 1 and the same three people matching you in the same order on every chromosome in the picture.

Let’s look at what this means and why we want to utilize a chromosome browser.

I selected three matches that I know are not all related through the same parent so I can demonstrate how confusing matches can be sorted out. Throughout this article, I’ve tried to explain each concept in at least two ways.

Please note that I’m using only chromsomes 1-4 as examples, not because they are any more, or less, important than the other chromosomes, but because showing all 22 would not add any benefit to the discussion. The X chromosome has a separate inheritance path and I wrote about that here.

Let’s start with a basic question.

Why Would I Want to Use a Chromosome Browser?

Genealogists view matches on chromosome browsers because:

  • We want to see where our matches match us on our chromosomes
  • We’d like to identify our common ancestor with our match
  • We want to assign a matching segment to a specific ancestor or ancestral line, which confirmed those ancestors as ours
  • When multiple people match us on the same location on the chromosome browser, that’s a hint telling us that we need to scrutinize those matches more closely to determine if those people match us on our maternal or paternal side which is the first step in assigning that segment to an ancestor

Once we accurately assign a segment to an ancestor, when anyone else matches us (and those other people) on that same segment, we know which ancestral line they match through – which is a great head start in terms of identifying our common ancestor with our new match.

That’s a genetic genealogy home run!

Home Runs 

There are four bases in a genetic genealogy home run.

  1. Determine whether you actually match someone on the same segment
  2. Which is the first step in determining that you match a group of people on the same segment
  3. And that you descend from a common ancestor
  4. The fourth step, or the home run, is to determine which ancestor you have in common, assigning that segment to that ancestor

If you can’t see segment information, you can’t use a chromosome browser and you can’t confirm the match on that segment, nor can you assign that segment to a particular ancestor, or ancestral couple.

The entire purpose of genealogy is to identify and confirm ancestors. Genetic genealogy confirms the paper trail and breaks down even more brick walls.

But before you can do that, you have to understand what matches mean and how to use them.

The first step is to understand that our chromosomes are double-sided and you can’ t see both of your chromosomes at once!

Double Sided – You Can’t See Both of Your Chromosomes at Once

The confusing part of the chromosome browser is that it can only “see” your two chromosomes blended as one. They are both there, but you just can’t see them separately.

Here’s the important concept:

You have 2 copies of chromosomes 1 through 22 – one copy that you received from your mother and one from your father, but you can’t “see” them separately.

When your DNA is sequenced, your DNA from your parents’ chromosomes emerges as if it has been through a blender. Your mother’s chromosome 1 and your father’s chromosome 1 are blended together. That means that without additional information, the vendor can’t tell which matches are from your father’s side and which are from your mother’s side – and neither can you.

All the vendor can tell is that someone matches you on the blended version of your parents. This isn’t a negative reflection on the vendors, it’s just how the science works.

Chromosome 1.png

Applying this to chromosome 1, above, means that each segment from each person, the blue person, the red person and the teal person might match you on either one of your chromosomes – the paternal chromosome or the maternal chromosome – but because the DNA of your mother and father are blended – there’s no way without additional information to sort your chromosome 1 into a maternal and paternal “side.”

Hence, you’re viewing “one” copy of your combined chromosomes above, but it’s actually “two-sided” with both maternal and paternal matches displayed in the chromosome browser.

Parent-Child Matches

Let’s explain this another way.

Chromosome parent.png

The example above shows one of my parents matching me. Don’t be deceived by the color blue which is selected randomly. It could be either parent. We don’t know.

You can see that I match my parent on the entire length of chromosome 1, but there is no way for me to tell if I’m looking at my mother’s match or my father’s match, because both of my parents (and my children) will match me on exactly the same locations (all of them) on my chromosome 1.

Chromosome parent child.png

In fact, here is a combination of my children and my parents matching me on my chromosome 1.

To sort out who is matching on paternal and maternal chromosomes, or the double sides, I need more information. Let’s look at how inheritance works.

Stay with me!

Inheritance Example

Let’s take a look at how inheritance works visually, using an example segment on chromosome 1.

Chromosome inheritance.png

In the example above:

  • The first column shows addresses 1-10 on chromosome 1. In this illustration, we are only looking at positions, chromosome locations or addresses 1-10, but real chromosomes have tens of thousands of addresses. Think of your chromosome as a street with the same house numbers on both sides. One side is Mom’s and one side is Dad’s, but you can’t tell which is which by looking at the house numbers because the house numbers are identical on both sides of the street.
  • The DNA pieces, or nucleotides (T, A, C or G,) that you received from your Mom are shown in the column labeled Mom #1, meaning we’re looking at your mother’s pink chromosome #1 at addresses 1-10. In our example she has all As that live on her side of the street at addresses 1-10.
  • The DNA pieces that you received from your Dad are shown in the blue column and are all Cs living on his side of the street in locations 1-10.

In other words, the values that live in the Mom and Dad locations on your chromosome streets are different. Two different faces.

However, all that the laboratory equipment can see is that there are two values at address 1, A and C, in no particular order. The lab can’t tell which nucleotide came from which parent or which side of the street they live on.

The DNA sequencer knows that it found two values at each address, meaning that there are two DNA strands, but the output is jumbled, as shown in the First and Second read columns. The machine knows that you have an A and C at the first address, and a C and A at the second address, but it can’t put the sequence of all As together and the sequence of all Cs together. What the sequencer sees is entirely unordered.

This happens because your maternal and paternal DNA is mixed together during the extraction process.

Chromosome actual

Click to enlarge image.

Looking at the portion of chromosome 1 where the blue and teal people both match you – your actual blended values are shown overlayed on that segment, above. We don’t know why the blue and the teal people are matching you. They could be matching because they have all As (maternal), all Cs (paternal) or some combination of As and Cs (a false positive match that is identical by chance.)

There are only two ways to reassemble your nucleotides (T, A, C, and G) in order and then to identify the sides as maternal and paternal – phasing and matching.

As you read this next section, it does NOT mean that you must have a parent for a chromosome browser to be useful – but it does mean you need to understand these concepts.

There are two types of phasing.

Parental Phasing

  • Parental Phasing is when your DNA is compared against that of one or both parents and sorted based on that comparison.

Chromosome inheritance actual.png

Parental phasing requires that at least one parent’s DNA is available, has been sequenced and is available for matching.

In our example, Dad’s first 10 locations (that you inherited) on chromosome 1 are shown, at left, with your two values shown as the first and second reads. One of your read values came from your father and the other one came from your mother. In this case, the Cs came from your father. (I’m using A and C as examples, but the values could just as easily be T or G or any combination.)

When parental phasing occurs, the DNA of one of your parents is compared to yours. In this case, your Dad gave you a C in locations 1-10.

Now, the vendor can look at your DNA and assign your DNA to one parent or the other. There can be some complicating factors, like if both your parents have the same nucleotides, but let’s keep our example simple.

In our example above, you can see that I’ve colored portions of the first and second strands blue to represent that the C value at that address can be assigned through parental phasing to your father.

Conversely, because your mother’s DNA is NOT available in our example, we can’t compare your DNA to hers, but all is not lost. Because we know which nucleotides came from your father, the remaining nucleotides had to come from your mother. Hence, the As remain after the Cs are assigned to your father and belong to your mother. These remaining nucleotides can logically be recombined into your mother’s DNA – because we’ve subtracted Dad’s DNA.

I’ve reassembled Mom, in pink, at right.

Statistical/Academic Phasing

  • A second type of phasing uses something referred to as statistical or academic phasing.

Statistical phasing is less successful because it uses statistical calculations based on reference populations. In other words, it uses a “most likely” scenario.

By studying reference populations, we know scientifically that, generally, for our example addresses 1-10, we either see all As or all Cs grouped together.

Based on this knowledge, the Cs can then logically be grouped together on one “side” and As grouped together on the other “side,” but we still have no way to know which side is maternal or paternal for you. We only know that normally, in a specific population, we see all As or all Cs. After assigning strings or groups of nucleotides together, the algorithm then attempts to see which groups are found together, thereby assigning genetic “sides.” Assigning the wrong groups to the wrong side sometimes happens using statistical phasing and is called strand swap.

Once the DNA is assigned to physical “sides” without a parent or matching, we still can’t identify which side is paternal and which is maternal for you.

Statistical or academic phasing isn’t always accurate, in part because of the differences found in various reference populations and resulting admixture. Sometimes segments don’t match well with any population. As more people test and more reference populations become available, statistical/academic phasing improves. 23andMe uses academic phasing for ethnicity, resulting in a strand swap error for me. Ancestry uses academic phasing before matching.

By comparison to statistical or academic phasing, parental phasing with either or both parents is highly accurate which is why we test our parents and grandparents whenever possible. Even if the vendor doesn’t use our parents’ results, we certainly can!

If someone matches you and your parent too, you know that match is from that parent’s side of your tree.


The second methodology to sort your DNA into maternal and paternal sides is matching, either with or without your parents.

Matching to multiple known relatives on specific segments assigns those segments of your DNA to the common ancestor of those individuals.

In other words, when I match my first cousin, and our genealogy indicates that we share grandparents – assuming we match on the appropriate amount of DNA for the expected relationship – that match goes a long way to confirming our common ancestor(s).

The closer the relationship, the more comfortable we can be with the confirmation. For example, if you match someone at a parental level, they must be either your biological mother, father or child.

While parent, sibling and close relationships are relatively obvious, more distant relationships are not and can occur though unknown or multiple ancestors. In those cases, we need multiple matches through different children of that ancestor to reasonably confirm ancestral descent.

Ok, but how do we do that? Let’s start with some basics that can be confusing.

What are we really seeing when we look at a chromosome browser?

The Grey/Opaque Background is Your Chromosome

It’s important to realize that you will see as many images of your chromosome(s) as people you have selected to match against.

This means that if you’ve selected 3 people to match against your chromosomes, then you’ll see three images of your chromosome 1, three images of your chromosome 2, three images of your chromosome 3, three images of your chromosome 4, and so forth.

Remember, chromosomes are double-sided, so you don’t know whether these are maternal or paternal matches (or imposters.)

In the illustration below, I’ve selected three people to match against my chromosomes in the chromosome browser. One person is shown as a blue match, one as a red match, and one as a teal match. Where these three people match me on each chromosome is shown by the colored segments on the three separate images.

Chromosome 1.png

My chromosome 1 is shown above. These images are simply three people matching to my chromosome 1, stacked on top of each other, like cordwood.

The first image is for the blue person. The second image is for the red person. The third image is for the teal person.

If I selected another person, they would be assigned a different color (by the system) and a fourth stacked image would occur.

These stacked images of your chromosomes are NOT inherently maternal or paternal.

In other words, the blue person could match me maternally and the red person paternally, or any combination of maternal and paternal. Colors are not relevant – in other words colors are system assigned randomly.

Notice that portions of the blue and teal matches overlap at some of the same locations/addresses, which is immediately visible when using a chromosome browser. These areas of common matching are of particular interest.

Let’s look closer at how chromosome browser matching works.

What about those colorful bars?

Chromosome Browser Matching

When you look at your chromosome browser matches, you may see colored bars on several chromosomes. In the display for each chromosome, the same color will always be shown in the same order. Most people, unless very close relatives, won’t match you on every chromosome.

Below, we’re looking at three individuals matching on my chromosomes 1, 2, 3 and 4.

Chromosome browser.png

The blue person will be shown in location A on every chromosome at the top. You can see that the blue person does not match me on chromosome 2 but does match me on chromosomes 1, 3 and 4.

The red person will always be shown in the second position, B, on each chromosome. The red person does not match me on chromosomes 2 or 4.

The aqua person will always be shown in position C on each chromosome. The aqua person matches me on at least a small segment of chromosomes 1-4.

When you close the browser and select different people to match, the colors will change and the stacking order perhaps, but each person selected will always be consistently displayed in the same position on all of your chromosomes each time you view.

The Same Address – Stacked Matches

In the example above, we can see that several locations show stacked segments in the same location on the browser.

Chromosome browser locations.png

This means that on chromosome 1, the blue and green person both match me on at least part of the same addresses – the areas that overlap fully. Remember, we don’t know if that means the maternal side or the paternal side of the street. Each match could match on the same or different sides.

Said another way, blue could be maternal and teal could be paternal (or vice versa,) or both could be maternal or paternal. One or the other or both could be imposters, although with large segments that’s very unlikely.

On chromosome 4, blue and teal both match me on two common locations, but the teal person extends beyond the length of the matching blue segments.

Chromosome 3 is different because all three people match me at the same address. Even though the red and teal matching segments are longer, the shared portion of the segment between all three people, the length of the blue segment, is significant.

The fact that the stacked matches are in the same places on the chromosomes, directly above/below each other, DOES NOT mean the matches also match each other.

The only way to know whether these matches are both on one side of my tree is whether or not they match each other. Do they look the same or different? One face or two? We can’t tell from this view alone.

We need to evaluate!

Two Faces – Matching Can be Deceptive!

What do these matches mean? Let’s ask and answer a few questions.

  • Does a stacked match mean that one of these people match on my mother’s side and one on my father’s side?

They might, but stacked matches don’t MEAN that.

If one match is maternal, and one is paternal, they still appear at the same location on your chromosome browser because Mom and Dad each have a side of the street, meaning a chromosome that you inherited.

Remember in our example that even though they have the same street address, Dad has blue Cs and Mom has pink As living at that location. In other words, their faces look different. So unless Mom and Dad have the same DNA on that entire segment of addresses, 1-10, Mom and Dad won’t match each other.

Therefore, my maternal and paternal matches won’t match each other either on that segment either, unless:

  1. They are related to me through both of my parents and on that specific location.
  2. My mother and father are related to each other and their DNA is the same on that segment.
  3. There is significant endogamy that causes my parents to share DNA segments from their more distant ancestors, even though they are not related in the past few generations.
  4. The segments are small (segments less than 7cM are false matches roughly 50% of the time) and therefore the match is simply identical by chance. I wrote about that here. The chart showing valid cM match percentages is shown here, but to summarize, 7-8 cMs are valid roughly 46% of the time, 8-9 cM roughly 66%, 9-10 cM roughly 91%, 10-11 cM roughly 95, but 100 is not reached until about 20 cM and I have seen a few exceptions above that, especially when imputation is involved.

Chromosome inheritance match.png

In this inheritance example, we see that pink Match #1 is from Mom’s side and matches the DNA I inherited from pink Mom. Blue Match #2 is from Dad’s side and matches the DNA I inherited from blue Dad. But as you can see, Match #1 and Match #2 do not match each other.

Therefore, the address is only half the story (double-sided.)

What lives at the address is the other half. Mom and Dad have two separate faces!

Chromosome actual overlay

Click to enlarge image

Looking at our example of what our DNA in parental order really looks like on chromosome 1, we see that the blue person actually matches on my maternal side with all As, and the teal person on the paternal side with all Cs.

  • Does a stacked match on the chromosome browser mean that two people match each other?

Sometimes it happens, but not necessarily, as shown in our example above. The blue and teal person would not match each other. Remember, addresses (the street is double-sided) but the nucleotides that live at that address tell the real story. Think two different looking faces, Mom’s and Dad’s, peering out those windows.

If stacked matches match each other too – then they match me on the same parental side. If they don’t match each other, don’t be deceived just because they live at the same address. Remember – Mom’s and Dad’s two faces look different.

For example, if both the blue and teal person match me maternally, with all As, they would also match each other. The addresses match and the values that live at the address match too. They look exactly the same – so they both match me on either my maternal or paternal side – but it’s up to me to figure out which is which using genealogy.

Chromosome actual maternal.png

Click to enlarge image

When my matches do match each other on this segment, plus match me of course, it’s called triangulation.

Triangulation – Think of 3

If my two matches match each other on this segment, in addition to me, it’s called triangulation which is genealogically significant, assuming:

  1. That the triangulated people are not closely related. Triangulation with two siblings, for example, isn’t terribly significant because the common ancestor is only their parents. Same situation with a child and a parent.
  2. The triangulated segments are not small. Triangulation, like matching, on small segments can happen by chance.
  3. Enough people triangulate on the same segment that descends from a common ancestor to confirm the validity of the common ancestor’s identity, also confirming that the match is identical by descent, not identical by chance.

Chromosome inheritance triangulation.png

The key to determining whether my two matches both match me on my maternal side (above) or paternal side is whether they also match each other.

If so, assuming all three of the conditions above are true, we triangulate.

Next, let’s look at a three-person match on the same segment and how to determine if they triangulate.

Three Way Matching and Identifying Imposters

Chromosome 3 in our example is slightly different, because all three people match me on at least a portion of that segment, meaning at the same address. The red and teal segments line up directly under the blue segment – so the portion that I can potentially match identically to all 3 people is the length of the blue segment. It’s easy to get excited, but don’t get excited quite yet.

Chromosome 3 way match.png

Given that three people match me on the same street address/location, one of the following three situations must be true:

  • Situation 1- All three people match each other in addition to me, on that same segment, which means that all three of them match me on either the maternal or paternal side. This confirms that we are related on the same side, but not how or which side.

Chromosome paternal.png

In order to determine which side, maternal or paternal, I need to look at their and my genealogy. The blue arrows in these examples mean that I’ve determined these matches to all be on my father’s side utilizing a combination of genealogy plus DNA matching. If your parent is alive, this part is easy. If not, you’ll need to utilize common matching and/or triangulation with known relatives.

  • Situation 2 – Of these three people, Cheryl, the blue bar on top, matches me but does not match the other two. Charlene and David, the red and teal, match each other, plus me, but not Cheryl.

Chromosome maternal paternal.png

This means that at least either my maternal or paternal side is represented, given that Charlene and David also match each other. Until I can look at the identity of who matches, or their genealogy, I can’t tell which person or people descend from which side.

In this case, I’ve determined that Cheryl, my first cousin, with the pink arrow matches me on Mom’s side and Charlene and David, with the blue arrows, match me on Dad’s side. So both my maternal and paternal sides are represented – my maternal side with the pink arrow as well as my father’s side with the blue arrows.

If Cheryl was a more distant match, I would need additional triangulated matches to family members to confirm her match as legitimate and not a false positive or identical by chance.

  • Situation 3 – Of the three people, all three match me at the same addresses, but none of the three people match each other. How is this even possible?

Chromosome identical by chance.png

This situation seems very counter-intuitive since I have only 2 chromosomes, one from Mom and one from Dad – 2 sidesof the street. It is confusing until you realize that one match (Cheryl and me, pink arrow) would be maternal, one would be paternal (Charlene and me, blue arrow) and the third (David and me, red arrows) would have DNA that bounces back and forth between my maternal and paternal sides, meaning the match with David is identical by chance (IBC.)

This means the third person, David, would match me, but not the people that are actually maternal and paternal matches. Let’s take a look at how this works

Chromosome maternal paternal IBC.png

The addresses are the same, but the values that live at the addresses are not in this third scenario.

Maternal pink Match #1 is Cheryl, paternal blue Match #2 is Charlene.

In this example, Match #3, David, matches me because he has pink and blue at the same addresses that Mom and Dad have pink and blue, but he doesn’t have all pink (Mom) nor all blue (Dad), so he does NOT match either Cheryl or Charlene. This means that he is not a valid genealogical match – but is instead what is known as a false positive – identical by chance, not by descent. In essence, a wily genetic imposter waiting to fool unwary genealogists!

In his case, David is literally “two-faced” with parts of both values that live in the maternal house and the paternal house at those addresses. He is a “two-faced imposter” because he has elements of both but isn’t either maternal or paternal.

This is the perfect example of why matching and triangulating to known and confirmed family members is critical.

All three people, Cheryl, Charlene and David match me (double sided chromosomes), but none of them match each other (two legitimate faces – one from each parent’s side plus one imposter that doesn’t match either the legitimate maternal or paternal relatives on that segment.)

Remember Three Things

  1. Double-Sided – Mom and Dad both have the same addresses on both sides of each chromosome street.
  2. Two Legitimate Faces – The DNA values, nucleotides, will have a unique pattern for both your Mom and Dad (unless they are endogamous or related) and therefore, there are two legitimate matching patterns on each chromsome – one for Mom and one for Dad. Two legitimate and different faces peering out of the houses on Mom’s side and Dad’s side of the street.
  3. Two-Faced Imposters – those identical by chance matches which zig-zag back and forth between Mom and Dad’s DNA at any given address (segment), don’t match confirmed maternal and paternal relatives on the same segment, and are confusing imposters.

Are you ready to hit your home run?

What’s Next?

Now that we understand how matching and triangulation works and why, let’s put this to work at the vendors. Join me for my article in a few days, Triangulation in Action at Family Tree DNA, MyHeritage, 23andMe and GedMatch.

We will step through how triangulation works at each vendor. You’ll have matches at each vendor that you don’ t have elsewhere. If you haven’t transferred your DNA file yet, you still have time with the step by step instructions below:



I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

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Genealogy Research

Crossovers: Frequency and Inheritance Statistics – Male Versus Female Matters

Recently, a reader asked if I had any crossover statistics.

They were asking about the number of crossovers, meaning divisions on each chromosome, of the parent’s DNA when a child is created. In other words, how many segments of your maternal and paternal grandparent’s DNA do you inherit from your mother and father – and are those numbers somehow different?

Why would someone ask that question, and how is it relevant for genealogists?

What is a Crossover and Why is it Important?

We know that every child receives half of their autosomal DNA from their father, and half from their mother. Conversely that means that each parent can only give their child half of their own DNA that they received from their parents. Therefore, each parent has to combine some of the DNA from their father’s chromosome and their mother’s chromosome into a new chromosome that they contribute to their child.

Crossovers are breakpoints that are created when the DNA of the person’s parents is divided into pieces before being recombined into a new chromosome and passed on to the person’s child.

I’m going to use the following real-life scenario to illustrate.

Crossover pedigree.png

The colors of the people above are reflected on the chromosome below where the DNA of the blue daughter, and her red and green parents are compared to the DNA of the tester. The tester is shown as the gray background chromosomes in the chromosome browser. The backgroud person is whose results we are looking at.

My granddaughter has tested her DNA, as have her parents and 3 of her 4 grandparents along with 2 great-grandparents, shown as red and green in the diagram above.

Here’s an example utilizing the FamilyTreeDNA chromosome browser.

Crossover example chr 1.png

On my granddaughter’s chromosome 1, on the chromosome brower above, we see two perfect examples of crossovers.

There’s no need to compare her DNA against that of her parent, the son in the chart above, because we already know she matches the full length of every chromosome with both of her parents.

However, when comparing my granddaughter’s DNA against the grandmother (blue) and her grandmother’s parents, the great-grandmother shown in red and great-grandfather shown in green, we can see that the granddaughter received her blue segments from the grandmother.

The grandmother had to receive that entire blue segment from either her mother, in red, or her father, in green. So, every blue segment must have an exactly matching red segment, green segment or combination of both.

The first red box at left shows that the blue segment was inherited partially from the grandmother’s red mother and green father. We know that because the tester matches the red great-grandmother on part of that blue segment and the green great-grandfather on a different part of the entire blue segment that the tester inherited from her blue grandmother.

The middle colored region, not boxed, shows the entire blue segment was inherited from the red great-grandmother and the blue grandmother passed that intact through her son to her granddaughter.

The third larger red boxed area encompassing the entire tested region to the right of the centromere was inherited by the granddaughter from her grandmother (blue segment) but it was originally from the blue grandmother’s red mother and green father.

The Crossover

The areas on this chromosome where the blue is divided between the red and green, meaning where the red and green butt up against each other is called a crossover. It’s literally where the DNA of the blue daughter crosses over between DNA contributed by her red mother and green father.

Crossover segments.png

In other words, the crossover where the DNA divided between the blue grandmother’s parents when the grandmother’s son was created is shown by the dark arrows above. The son gave his daughter that exact same segment from his mother and it’s only by comparing the tester’s DNA against her great-grandparents that we can see the crossover.

Crossover 4 generations.png

What we’re really seeing is that the segments inherited by the grandmother from her parents two different chromosomes were combined into one segment that the grandmother gave to her son. The son inherited the green piece and the red piece on his maternal chromosome, which he gave intact to his daughter, which is why the daughter matches her grandmother on that entire blue segment and matches her great-grandparents on the red and green pieces of their individual DNA.

Inferred Matching Segments

Crossover untested grandfather.png

The entirely uncolored regions are where the tester does not match her blue grandmother and where she would match her grandfather, who has not tested, instead of her blue grandmother.

The testers father only received his DNA from his mother and father, and if his daughter does not match his mother, then she must match his untested father on that segment.

Looking at the Big Inheritance Picture

The tester’s full autosomal match between the blue grandmother, red great-grandmother and green great-grandfather is shown below.

Crossover autosomes.png

In light of the discussion that follows, it’s worth noting that chromosomes 4 and 20 (orange arrows) were passed intact from the blue grandmother to the tester through two meiosis (inheritance) events. We know this because the tester matches the green great-grandfather’s DNA entirely on these two chromosomes that he passed to his blue daughter, her son and then the tester.

Let’s track this for chromosomes 4 and 20:

  • Meiosis 1 –The tester matches her blue grandmother, so we know that there was no crossover on that segment between the father and the tester.
  • Meiosis 2 – The tester matches her green great-grandfather along the entire chromosome, proving that it was passed intact from the grandmother to the tester’s father, her son.
  • What we don’t know is whether there were any crossovers between the green great-grandfather when he passed his parent or parents DNA to the blue grandmother, his daughter. In order to determine that, we would need at least one of the green great-grandfather’s parents, which we don’t have. We don’t know if the green great-grandfather passed on his maternal or paternal copy of his chromosome, or parts of each to the blue great-grandmother, his daughter.

Meiosis Events and the Tree

So let’s look at these meiosis or inheritance events in a different way, beginning at the bottom with the pink tester and counting backwards, or up the tree.

Crossover meiosis events.png

By inference, we know that chromosomes 11, 16 and 22 (purple arrows) were also passed intact, but not from the blue grandmother. The tester’s father passed his father’s chromosome intact to his daughter. That’s the untested grandfather again. We know this because the tester does not match her blue grandmother at all on either of these three chromosomes, so the tester must match her untested grandfather instead, because those are the only two sources of DNA for the tester’s father.

A Blip, or Not?

If you’ve noticed that chromosome 14 looks unusual, in that the tester matches her grandmother’s blue segment, but not either of her great-grandparents, which is impossible, give yourself extra points for your good eye.

In this case, the green great-grandfather’s kit was a transfer kit in which that portion of chromosome 14 was not included or did not read accurately. Given that the red great-grandmother’s kit DID read in that region and does not match the tester, we know that chromosome 14 would actually have a matching green segment exactly the size of the blue segment.

However, in another situation where we didn’t know of an issue with the transfer kit, it is also possible that the granddaughter matched a small segment of the blue grandmother’s DNA where they were identical by chance. In that case, chromosome 14 would actually have been passed to the tester intact from her father’s father, who is untested.

Every Segment has a Story

Looking at this matching pattern and our ability to determine the source of the DNA back several generations, originating from great-grandparents, I hope you’re beginning to get a sense of why understanding crossovers better is important to genealogists.

Every single segment has a story and that story is comprised of crossovers where the DNA of our ancestors is combined in their offspring. Today, we see the evidence of these historical genetic meiosis or division/recombination events in the start and end points of matches to our genetic cousins. Every start and end point represents a crossover sometime in the past.

What else can we tell about these events and how often they occur?

Of the 22 autosomes, not counting the X chromosome which has a unique inheritance pattern, 17 chromosomes experienced at least one crossover.

What does this mean to me as a genealogist and how can I interpret this type of information?

Philip Gammon

You may remember our statistician friend Philip Gammon. Philip and I have collaborated before authoring the following articles where Philip did the heavy lifting.

I discussed crossovers in the article Concepts – DNA Recombination and Crossovers, also in collaboration with Philip, and showed several examples in a Four Generation Inheritance Study.

If you haven’t read those articles, now might be a good time to do so, as they set the stage for understanding the rest of this article.

The frequency of chromosome segment divisions and their resulting crossovers are key to understanding how recombination occurs, which is key to understanding how far back in time a common ancestor between you and a match can expect to be found.

In other words, everything we think we know about relationships, especially more distant relationships, is predicated on the rate that crossovers occur.

The Concepts article references the Chowdhury paper and revealed that females average about 42 crossovers per child and males average about 27 but these quantities refer to the total number of crossovers on all 22 autosomes and reveal nothing about the distribution of the number of crossovers at the individual chromosome level.

Philip Gammon has been taking a closer look at this particular issue and has done some very interesting crossover simulations by chromosome, which are different sizes, as he reports beginning here.

Crossover Statistics by Philip Gammon

For chromosomes there is surprisingly little information available regarding the variation in the number of crossovers experienced during meiosis, the process of cell division that results in the production of ova and sperm cells. In the scientific literature I have been able to find only one reference that provides a table showing a frequency distribution for the number of crossovers by chromosome.

The paper Broad-Scale Recombination Patterns Underlying Proper Disjunction in Humans by Fledel-Alon et al in 2009 contains this information tucked away at the back of the “Supplementary methods, figures, and tables” section. It was likely not produced with genetic genealogists in mind but could be of great interest to some. The columns X0 to X8 refer to the number of crossovers on each chromosome that were measured in parental transmissions. Separate tables are shown for male and female transmissions because the rates between the two sexes differ significantly. Note that it’s the gender of the parent that matters, not the child. The sample size is quite small, containing only 288 occurrences for each gender.

A few years ago I stumbled across a paper titled Escape from crossover interference increases with maternal age by Campbell et al 2015. This study investigated the properties of crossover placement utilising family groups contained within the database of the direct-to-consumer genetic testing company 23andMe. In total more than 645,000 well-supported crossover events were able to be identified. Although this study didn’t directly report the observed frequency distribution of crossovers per chromosome, it did produce a table of parameters that accurately described the distribution of inter-crossover distances for each chromosome.

By introducing these parameters into a model that I had developed to implement the equations described by Housworth and Stahl in their 2003 paper Crossover Interference in Humans I was able to derive tables depicting the frequency of crossovers. The following results were produced for each chromosome by running 100,000 simulations in my crossover model:

Crossover transmissions from female to child.png

Transmissions from female parent to child, above.

Crossover transmissions male to child.png

Transmissions from male parent to child.

To be sure that we understand what these tables are revealing let’s look at the first row of the female table. The most frequent outcome for chromosome #1 is that there will be three crossovers and this occurs 27% of the time. There were instances when up to 10 crossovers were observed in a single meiosis but these were extremely rare. Cells that are blank recorded no observations in the 100,000 simulations. On average there are 3.36 crossovers observed on chromosome #1 in female to child transmissions i.e. the female chromosome #1 is 3.36 Morgans (336 centimorgans) in genetic length.

Blaine Bettinger has since examined crossover statistics using crowdsourced data in The Recombination Project: Analyzing Recombination Frequencies Using Crowdsourced Data, but only for females. His sample size was 250 maternal transmissions and Table 2 in the report presents the results in the same format as the tables above. There is a remarkable degree of conformity between Blaine’s measurements and the output from my simulation model and also to the earlier Fledel-Alon et al study.

The diagrams below are a typical representation of the chromosomes inherited by a child.

Crossovers inherited from mother.jpg

The red and orange (above) are the set of chromosomes inherited from the mother and the aqua and green (below) from the father. The locations where the colours change identify the crossover points.

It’s worth noting that all chromosomes have a chance of being passed from parent to child without recombination. These probabilities are found in the column for zero crossovers.

In the picture above the mother has passed on two red chromosomes (#14 and #20) without recombination from one of the maternal grandparents. No yellow chromosomes were passed intact.

Similarly, below, the father has passed on a total of five chromosomes that have no crossover points. Blue chromosomes #15, #18 and #21 were passed on intact from one paternal grandparent and green chromosomes #4 and #20 from the other.

Crossovers inherited from father.jpg

It’s quite a rare event for one of the larger chromosomes to be passed on without recombination (only a 1.4% probability for chromosome #1 in female transmissions) but occurs far more frequently in the smaller chromosomes. In fact, the male chromosome #21 is passed on intact more often (50.6% of the time) than containing DNA from both of the father’s parents.

However, there is nothing especially significant about chromosome #21.

The same could be said for any region of similar genetic length on any of the autosomes i.e. the first 52 cM of chromosome #1 or the middle 52 cM of chromosome #10 etc. From my simulations I have observed that on average 2.8 autosomes are passed down from a mother to child without a crossover and an average of 5.1 autosomes from a father to child.

In total (from both parents), 94% of offspring will inherit between 4 and 12 chromosomes containing DNA exclusively from a single grandparent. In the 100,000 simulations the child always inherited at least one chromosome without recombination.

Back to Roberta

If you have 3 generations who have tested, you can view the crossovers in the grandchild as compared to either one or two grandparents.

If the child doesn’t match one grandparent, even if their other grandparent through that parent hasn’t tested, you can certainly infer that any DNA where the grandchild doesn’t match the available grandparent comes from the non-tested “other” grandparent on that side.

Let’s Look at Real-Life Examples

Using the example of my 2 granddaughters, both of their parents and 3 of their 4 grandparents have tested, so I was able to measure the crossovers that my granddaughters experienced from all 4 of their grandparents.

Maternal Crossovers Granddaughter 1 Granddaughter 2 Average
Chromosome 1 6 2 3.36
Chromosome 2 4 2 3.17
Chromosome 3 3 2 2.71
Chromosome 4 2 2 2.59
Chromosome 5 2 1 2.49
Chromosome 6 4 2 2.36
Chromosome 7 3 1 2.23
Chromosome 8 2 2 2.11
Chromosome 9 3 1 1.95
Chromosome 10 4 2 2.08
Chromosome 11 3 0 1.93
Chromosome 12 3 3 2.00
Chromosome 13 1 1 1.52
Chromosome 14 3 1 1.38
Chromosome 15 4 1 1.44
Chromosome 16 2 2 1.58
Chromosome 17 2 2 1.53
Chromosome 18 2 0 1.40
Chromosome 19 2 1 1.18
Chromosome 20 0 1 1.19
Chromosome 21 0 1 0.74
Chromosome 22 1 0 0.78
Total 56 30 41.71

Looking at these results, it’s easy to see just how different inheritance between two full siblings can be. Granddaughter 1 has 56 crossovers through her mother, significantly more than the average of 41.71. Granddaughter 2 has 30, significantly less than average.

The average of the 2 girls is 43, very close to the total average of 41.71.

Note that one child received 2 chromosomes intact from her mother, and the other received 3.

Paternal Crossovers Granddaughter 1 Granddaughter 2 Average
Chromosome 1 2 2 1.98
Chromosome 2 3 2 1.85
Chromosome 3 2 2 1.64
Chromosome 4 0 1 1.46
Chromosome 5 1 2 1.46
Chromosome 6 2 1 1.41
Chromosome 7 1 2 1.36
Chromosome 8 1 1 1.23
Chromosome 9 1 3 1.26
Chromosome 10 3 2 1.30
Chromosome 11 0 1 1.20
Chromosome 12 1 1 1.32
Chromosome 13 2 1 1.02
Chromosome 14 1 0 0.97
Chromosome 15 1 2 1.01
Chromosome 16 0 1 1.02
Chromosome 17 0 0 1.06
Chromosome 18 1 1 0.98
Chromosome 19 1 1 1.00
Chromosome 20 0 0 0.99
Chromosome 21 0 0 0.52
Chromosome 22 0 0 0.63
Total 23 26 26.65

Granddaughter 2 had slightly more paternal crossovers than did granddaughter 1.

One child received 7 chromosomes intact from her father, and the other received 5.

Chromosome Granddaughter 1 Maternal Granddaughter 1 Paternal
Chromosome 1 6 2
Chromosome 2 4 3
Chromosome 3 3 2
Chromosome 4 2 0
Chromosome 5 2 1
Chromosome 6 4 2
Chromosome 7 3 1
Chromosome 8 2 1
Chromosome 9 3 1
Chromosome 10 4 3
Chromosome 11 3 0
Chromosome 12 3 1
Chromosome 13 1 2
Chromosome 14 3 1
Chromosome 15 4 1
Chromosome 16 2 0
Chromosome 17 2 0
Chromosome 18 2 1
Chromosome 19 2 1
Chromosome 20 0 0
Chromosome 21 0 0
Chromosome 22 1 0
Total 56 23

Comparing each child’s maternal and paternal crossovers side by side, we can see that Granddaughter 1 has more than double the number of maternal as compared to paternal crossovers, while Granddaughter 2 only had slightly more.

Chromosome Granddaughter 2 Maternal Granddaughter 2 Paternal
Chromosome 1 2 2
Chromosome 2 2 2
Chromosome 3 2 2
Chromosome 4 2 1
Chromosome 5 1 2
Chromosome 6 2 1
Chromosome 7 1 2
Chromosome 8 2 1
Chromosome 9 1 3
Chromosome 10 2 2
Chromosome 11 0 1
Chromosome 12 3 1
Chromosome 13 1 1
Chromosome 14 1 0
Chromosome 15 1 2
Chromosome 16 2 1
Chromosome 17 2 0
Chromosome 18 0 1
Chromosome 19 1 1
Chromosome 20 1 0
Chromosome 21 1 0
Chromosome 22 0 0
Total 30 26

Granddaughter 2 has closer to the same number of maternal and paternal of crossovers, but about 8% more maternal.

Comparing Maternal and Paternal Crossover Rates

Given that males clearly have a much, much lower crossover rate, according to the Philip’s chart as well as the evidence in just these two individual cases, over time, we would expect to see the DNA segments significantly LESS broken up in male to male transmissions, especially an entire line of male to male transmissions, as compared to female to female linear transmissions. This means we can expect to see larger intact shared segments in a male to male transmission line as compared to a female to female transmission line.

  G1 Mat G2 Mat Mat Avg G1 Pat G2 Pat Pat Avg
Gen 1 56 30 41.71 23 26 26.65
Gen 2 112 60 83.42 46 52 53.30
Gen 3 168 90 125.13 69 78 79.95
Gen 4 224 120 166.84 92 104 106.60

Using the Transmission rates for Granddaughter 1, Granddaughter 2, and the average calculated by Philip, it’s easy to see the cumulative expected average number of crossovers vary dramatically in every generation.

By the 4th generation, the maternal crossovers seen in someone entirely maternally descended at the rate of Grandchild 1 would equal 224 crossovers meaning that the descendant’s DNA would be divided that many times, while the same number of paternal linear divisions at 4 generations would only equal 92.

Yet today, we would never look at 2 people’s DNA, one with 224 crossovers compared to one with 92 crossovers and even consider the possibility that they are both only three generations descended from an ancestor, counting the parents as generation 1.

What Does This Mean?

The number of males and females in a specific line clearly has a direct influence on the number of crossovers experienced, and what we can expect to see as a result in terms of average segment size of inherited segments in a specific number of generations.

Using Granddaughter 1’s maternal crossover rate as an example, in 4 generations, chromosome 1 would have incurred a total of 24 crossovers, so the DNA would be divided into in 25 pieces. At the paternal rate, only 8 crossovers so the DNA would be in 9 pieces.

Chromosome 1 is a total of 267 centimorgans in length, so dividing 267 cM by 25 would mean the average segment would only be 10.68 cM for the maternal transmission, while the average segment divided by 9 would be 29.67 cM in length for the paternal transmission.

Given that the longest matching segment is a portion of the estimated relationship calculation, the difference between a 10.68 cM maternal linear segment match and a 29.67 paternal linear cM segment match is significant.

While I used the highest and lowest maternal and paternal rates of the granddaughters, the average would be 19 and 29, respectively – still a significant difference.

Maternal and Paternal Crossover Average Segment Size

Each person has an autosomal total of 3374 cM on chromosomes 1-22, excluding the X chromosome, that is being compared to other testers. Applying these calculations to all 22 autosomes using the maternal and paternal averages for 4 generations, dividing into the 3374 total we find the following average segment centiMorgan matches:

Crossovers average segment size.png

Keep in mind, of course, that the chart above represents 3 generations in a row of either maternal or paternal crossovers, but even one generation is significant.

The average size segment of a grandparent’s DNA that a child receives from their mother is 80.89 cM where the average segment of a grandparent’s DNA inherited from their father is 1.57 times larger at 126.6 cM.

Keep the maternal versus paternal inheritance path in mind as you evaluate matches to cousins with identified common ancestors, especially if the path is entirely or mostly maternal or paternal.

For unknown matches, just keep in mind that the average that vendors calculate and use to predict relationships, because they can’t and don’t have “inside knowledge” about the inheritance path, may or may not be either accurate or average. They do the best they can do with the information they have at hand.

Back to Philip again who provides us with additional information.

Maternal Versus Paternal Descent

Along a predominantly maternal path the DNA is likely to be inherited in more numerous smaller segments while along a predominantly paternal path it will likely be in fewer but larger segments. So matches who descend paternally from a common ancestor and carry the surname are not likely to carry more DNA from that common male ancestor than someone who descends from a mixed or directly maternal line. In fact, someone descending from an ancestor down an all-male path is more likely to inherit no DNA at all from that ancestor than someone descending down an all-female path. This is because the fewer segments there are the higher the risk is that a person won’t pass on any of them. Of course, there’s also a greater chance that all of the segments could be passed on. Fewer segments leads to more variation in the amount of DNA inherited but not a higher average amount of DNA inherited.

Gammon 3X great-grandparents.png

The chart above shows the spread in the amount of DNA inherited from a 3xgreat-grandparent, down all-maternal, all-paternal and down all possible paths. The average in each case is 3.125% i.e. 1 part in 32 but as expected the all-paternal path shows much more variation. Compared to the all-maternal path, on the all-paternal you are more likely to inherit either less than 2.0% or more than 5.0%. In 50,000 simulations there were 14 instances where a 3xgreat-grandchild did not inherit any DNA down the all-paternal path. There were no cases of zero DNA inherited down the all-maternal path.

One way to think about this is to consider a single chromosome. If at least one crossovers occurs in the meiosis some DNA from each grandparent will be passed down to the grandchild but when it is passed on without recombination, as occurs more frequently in paternal than maternal meiosis, all of the DNA from one grandparent is passed on but none at all from the other. When this happens, there is no bias toward either the grandfather’s or the grandmother’s chromosome being passed on. It’s just as likely that the segment coming down the all-paternal path will be lost entirely as it is that it will be passed on in full.



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DNAPainter: Painting Leeds Method Matches

Last week, I wrote about how I utilized the Leeds Method in the article, The Leeds Method. What I didn’t say is that I was sizing up the Leeds Method for how I could use the technique to paint additional segments of my chromosomes.

The Leeds Method divides your matches into four groups, one attributable to each grandparent. That means those matches can be painted to your four sets of great-grandparents, assuming you can identify the maternal and paternal groups. Hint – Y and mitochondrial DNA matching or haplogroups may help if you have no better hints.

For genealogists who know who their grandparents are, testing close relatives and cousins is a must in order to be able to associate matches with your four grandparents’ lines.

Please note that the Leeds method generates hints for genealogists by grouping people according to common matches. We must further evaluate those matches by doing traditional genealogy and by looking for segments that triangulate. The Leeds method in conjunction with the actual match results at vendors, combined with DNAPainter helps us do just that.

Utilizing DNAPainter

Since I’ve been able to sort matches into maternal and paternal “sides” using the Leeds Method, which in essence parentally phases the matches, I can use DNAPainter to paint them. Here are my four articles I wrote about how to utilize DNAPainter.

DNAPainter – Chromosome Sudoku for Genetic Genealogy Addicts 
DNAPainter – Touring the Chromosome Garden 
DNAPainter – Mining Vendor Matches to Paint Your Chromosomes 
Proving or Disproving a Half Sibling Relationship Using DNAPainter

Combining the Two Tools

DNAPainter has the potential to really utilize the Leeds Method results, other than Ancestry matches of course. Ancestry does not provide segment information. (Yes, I know, dead horse but I still can’t resist an occasional whack.)

You’re going to utilize your spreadsheet groupings to paint the DNA from each individual match at the vendors to DNAPainter.

On the spreadsheet, if these matches are from Family Tree DNA, MyHeritage, 23andMe or GedMatch, you’ll copy the matching segments from that vendor and paint those matching segments at DNAPainter. I explained how to do that in the articles about DNAPainter.

I do not use mass uploads to DNAPainter, because it’s impossible to assign those to different sides of your tree or ancestors. I paint individual matches, including information about the match and what I know about the history of the segment itself or associated ancestor.

I only paint segments that I can identify with certainty as maternal or paternal.

Pushing Back in Time

Based on which segments of identified ancestors the Leeds matches overlap with at DNAPainter, I can push that segment information further back in time. The blessing of this is that these Leeds matches may well fill in several blanks in my chromosome that are not yet painted by people with whom I share identified ancestors.

Even if your maternal and paternal grandparents are intermarried on each side, as long as they are not intermarried across your parental lines (meaning mother & father,) then the Leeds Method will work fine for painting. Even if you think you are attributing a segment to your paternal grandmother, for example, and the person actually matches through your paternal grandfather, you’ve still painted them on the correct chromosome – meaning your paternal chromosome. As you build up that chromosome with matches, you’ll see soon enough if you have 9 matches attributed to John Doe and one to Jane Smith, the Jane Smith match is likely incorrectly attributed, those two lines are somehow interrelated or it’s a false positive match.

Because I work with only fairly large Leeds matches – nothing below 30 cM, I sometimes receive a nice gift in terms of painting large previously unpainted segments – like the one on my mother’s side, below.

Look at this large green segment on chromosome 19 that I painted thanks to one of the Leeds matches, Harold. (Note that the two long blue and brown bars at the bottom of each chromosome are my ethnicity, not matches.) Another benefit is that if a Leeds match matches on already identified segments assigned to ancestors, I’ve just identified which ancestral lines I share with that match.

The green Ferverda side match to Roland through the Leeds Method aligns partially with a segment already known to descend from Jacob Lentz and Frederica Ruhle who were born in the 1780s. I’m related to Roland somehow through that line, and by just looking at his (redacted here) surname, I *think* I know how, even though he doesn’t have a tree online. How cool is that!

Important Notes for DNAPainter

Word of caution here. I would NOT paint anyone who falls into multiple match groups without being able to identify ancestors. Multiple match groups may indicate multiple ancestors, even if you aren’t aware of that.

Each segment has its own history, so it’s entirely possible that multiple match groups are accurate. It’s also possible that to some extent, especially with smaller segments, that matches by chance come into play. That’s why I only work with segments above 30 cM when using the Leeds method where I know I’m safe from chance matches. You can read about identical by descent (IBD) and identical by chance (IBC) matches here.

What a DNAPainter Leeds Match Means

It’s very important to label segments in DNAPainter with the fact that the source was through the Leeds Method.

These painted matches DO NOT MEAN that the match descends from the grandparent you are associating with the match.

It means that YOU inherited your common DNA with this match FROM that grandparent. It suggests that your match descends from one of the ancestors of this couple, or possibly from your great-grandparents, but you don’t necessarily share this great-grandparent couple with your match.

That’s different than the way I normally paint my chromosomes – meaning only when a specific common ancestor has been identified. For someone painted from matches NOT identified through the Leeds Method, if I know the person descends from a grandparent, I paint them to the great-grandparent couple. People painted through the Leeds Method don’t necessarily share that couple, but do share an ancestor of that couple.

When I paint using the Leeds method, I’m assigning the match to a set of great-grandparents because I can’t genealogically identify the common ancestor further upstream, so I’m letting genetics tell me which genealogical quadrant they fall into on my tree. With the Leeds Method, I can tell which grandparent I inherited that DNA through. In my normal DNAPainter methodology, I ONLY paint matches when I’ve identified the common ancestor – so Leeds Method matches would not previously have qualified.

I don’t mean to beat this to death and explain it several ways – but it’s really important to understand the difference and when looking back, understand why you painted what you did.

Labeling Leeds Match Painted Segments

Therefore, with Leeds Method match painting, I identify the match name as “John Doe FTDNA Leeds-Ferverda” which tells me the matches name (John Doe,) where they tested (FTDNA) and why I painted them (Ferverda column in my Leeds spreadsheet,) even though I don’t know for sure which ancestor we actually have in common. I paint them to the parents of my Ferverda grandfather. Not John Ferverda, my grandfather, but to his parents, Hiram Ferverda and Eva Miller. I know I received my matching DNA through one of them – I just don’t know which person of that couple yet.

However, looking at who else is assigned to that segment with an identified common ancestor will tell me where in my tree that segment originated – for me. We still don’t know where in your matches tree that segment originated.

“Match To” Issues

Lastly, if you happen to select a “match to” person to represent one of your grandparent matches that just happens to be descended from two grandparent lines, you’ve had your bad luck for the month. Remember, your “match to” person is the first person (closest match) that hasn’t yet been grouped, so you don’t really select them. If you realize you’re getting goofy results, stop and undo those results, then select the next candidate as your “match to” person.

At one vendor, when I selected the first person who hadn’t yet been grouped and used them for the red column which turned out to be Bolton, about half of them overlapped with Estes segments that I’ve already painted and confirmed from several sources. Obviously, there’s a problem someplace, and I’m guessing it just happens to be the luck of the draw with the “match to” person being descended from both lines. The lines both lived in the same county for generations. I need to redo that section with someone whose tree I know positively descends from the Bolton line and does NOT intersect with another of my lines. However, I was able to identify that this issue existed because I’ve already painted multiple ancestor-confirmed cousins who carry those same segments – and I know where they came from.

These tools are just that – tools and require some level of analytical skill and common sense. In other words, it’s a good idea to stay with larger matches and know when to say “uh-oh.” If it doesn’t feel right, don’t paint it.

Breaking Down Distant Brick Walls

I’m still thinking about how to use the Leeds Method, probably in combination with DNAPainter, to break down brick walls. My brick walls aren’t close in time. Most of them are several generations back and revolve around missing female surnames, missing records or ancestors appearing in a new location with no ability to connect them back to the location/family they left.

In essence, I would need to be able to isolate the people matching that most distant ancestor couple, then look for common surnames and ancestors within that match group. The DNAGedcom.com client which allows you to sort matches by surname might well be an integral piece of this puzzle/solution. I’ll have to spend some time to see how well this works.

Solving this puzzle would be entirely dependent on people uploading their trees.

If you have thoughts on how to use these tools to break down distant brick walls, or devise a methodology, please let me know.

And if you haven’t uploaded your tree, please do.

Would I Do The Leeds Method Again?

Absolutely, at least for the vendors who provide segment information.

I painted 8 new Leeds matches from Family Tree DNA on my Ferverda grandparent side which increased the number of painted segments at DNAPainter from 689 to 704, filled in a significant number of blank spaces on my chromosomes, and took my total % DNA painted from 60 to 61%. I added the rest of my Leeds hints from Family Tree DNA of 30 cM or over, and increased my painted segments to 734 and my percentage to 62% I know that 1 or 2% doesn’t sound like a very big increase, but it’s scientific progress.

It’s more difficult to increase the number of new segments after you’ve painted much of your genome because many segments overlap segments already painted. So, a 2% increase is well worth celebrating!

Having said that, I would love for the vendors to provide this type of clustering so I don’t have to. To date, Family Tree DNA is the only vendor who does any flavor of automatically bucketing results in this fashion – meaning paternal and maternal, which is half the battle. I would like to see them expand to the four grandparents from the maternal/paternal matching they provide today.

We’ve been asking Ancestry for enhanced tools for years. There’s no reason they couldn’t in essence do what Dana has done along with provide the DNAgedcom.com search functionality. And yes…I still desperately want a chromosome browser or at least segment information.

I will continue to utilize the Leeds Method, at least with vendors other than Ancestry because it allows me to incorporate the results with DNAPainter. It’s somehow ironic that I started out grouping the Ancestry results, but wound up realizing that the results from other vendors, specifically Family Tree DNA and MyHeritage are significantly more useful due to the segment data and combined tools.

Getting the Most Bang for Your Buck

If you tested at Ancestry or 23andMe, I would strongly encourage you to download your raw data file from both of these vendors and transfer to Family Tree DNA, MyHeritage and GedMatch to get the most out of your DNA tests. Here is the step-by-step guide for how to download your DNA from Ancestry.

The uploads to those three locations are free. All tools are free at MyHeritage until December 1, 2018 when they will begin charging for more advanced tools. The upload is free at Family Tree DNA and the advanced tools, including the chromosome browser, only require a $19 unlock.

Here is the step-by-step guide for uploading to MyHeritage and to Family Tree DNA. Fishing in every pond is critically important. You never know what you’re missing otherwise!

How many segments of your DNA can you paint using the Leeds Method in combination with DNA Painter?



I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

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The Leeds Method

This is the first in a series of two articles. This article explains the Leeds Method and how I created a Leeds Spreadsheet in preparation for utilizing the results in DNAPainter. I stumbled around a bit, but I think I’ve found a nice happy medium and you can benefit from my false starts by not having to stumble around in the dark yourself. Of course, I’m telling you about the pitfalls I discovered.

The second article details the methodology I utilized to paint these matches, because they aren’t quite the same as “normal” matching segments with identified ancestors.

Welcome to the Leeds Method

Dana Leeds developed a novel way to utilize a spreadsheet for grouping your matches from second through fourth cousins and to assign them to “grandparent” quadrants with no additional or previous information. That’s right, this method generates groupings that can be considered good hints without any other information at all.

Needless to say, this is great for adoptees and those searching for a parent.

It’s also quite interesting for genetic genealogists as well. One of the best aspects is that it’s very easy to do and very visual. Translation – no math. No subtraction.

Caveat – it’s also not completely accurate 100% of the time, especially when you are dealing with more distant matches, intermarriage and/or endogamy. But there are ways to work around these issues, so read on!

You can click to enlarge any image.

I’ll be referring to this graphic throughout this article. It shows the first several people on my Ancestry match list, beginning with second cousins, using pseudonyms. I chose to use Ancestry initially because they don’t provide chromosome browsers or triangulation tools, so we need as much help there as we can get.

I’ve shown the surnames of my 4 grandparents in the header columns with an assigned color, plus a “Weird group” (grey) that doesn’t seem to map to any of the 4. People in that group are much more distant in my match list, so they aren’t shown here.

I list the known “Most Common Recent Ancestor,” when identified, along with the color code that so I can easily see who’s who.

All those blanks in the MCRA column – those are mostly people without trees. Just think how useful this would be if everyone who could provide a tree did!

What Does the Leeds Method Tell You?

The Leeds Method divides your matches into four colored quadrants representing each grandparent unless your genealogical lines are heavily intermarried. If you have lots of people who fall into both of two (or more) colors, that probably indicates intermarriage or a heavily endogamous population.

In order to create this chart, you work with your closest matches that are 2nd cousins or more distant, but no more distant than 4th cousins. For endogamous people, by the time you’re working in 4th cousins, you’ll have too much overlap, meaning people who fall into multiple columns, so you’ll want to work with primarily 2nd and 3rd cousins. The good news is that endogamous people tend to have lots of matches, so you should still have plenty to work with!


In this article, I’m using Dana’s method, with a few modifications.

By way of a very, very brief summary:

  • On a spreadsheet, you list all of your matches through at least third cousins
  • Then check each match to see who you match in common with them
  • Color code the results, in columns
  • Each person what you match in common with your closest cousin, Sleepy, is marked as yellow. Dopey and I both match Bashful and Jasmine in common and are colored Red. Doc and I both match Happy and Belle and are colored blue, and so forth.
  • The result is that each color represents a grandparent

To understand exactly what I’m doing, read Dana’s articles, then continue with this article.

DNA Color Clustering: The Leeds Method for Easily Visualizing Matches  
DNA Color Clustering: Identifying “In Common” Surnames 
DNA Color Clustering: Does it Work with 4th Cousins? By the way, yes it does, most of the time.
DNA Color Clustering: Dealing with 3 Types of Overlap

Why Use “The Leeds Method”?

In my case, I wanted to experiment. I wanted to see if this method works reliably and what could be done with the information if you already know a significant amount about your genealogy. And if you don’t.

The Leeds Method is a wonderful way to group people into 4 “grandparent” groups in order to search for in-common surnames. I love being able to perform this proof of concept “blind,” then knowing my genealogy and family connections well enough to be able to ascertain whether it did or didn’t work accurately.

If you can associate a match with a single grandparent, that really means you’ve pushed that match back to the great-grandparent couple.

That’s a lot of information without any genealogical knowledge in advance.

How Low Can You Go?

I have more than 1000 fourth cousins at Ancestry. This makes the task of performing the Leeds Method manually burdensome at that level. It means I would have had to type all 1000+ fourth cousins into a spreadsheet. I’m patient, but not that patient, at least not without a lot of return for the investment. I have to ask myself, exactly what would I DO with that information once they were grouped?

Would 4th cousin groupings provide me with additional information that second and third cousin groupings wouldn’t? I don’t think so, but you can be the judge.

After experimenting, I’d recommend creating a spreadsheet listing all of your 2nd and 3rd cousins, along with about 300 or so of your closest 4th cousin matches. Said another way, my results started getting somewhat unpredictable at about 40-45 cMs, although that might not hold true for others. (No, you can’t tell the longest matching segment length at Ancestry, but I could occasionally verify at the other vendors, especially when people from Ancestry have transferred.)

Therefore, I only proceeded through third cousins and about 300 of the Ancestry top 4th cousin matches.

I didn’t just utilize this methodology with Ancestry, but with Family Tree DNA, MyHeritage and 23andMe as well. I didn’t use GedMatch because those matches would probably have tested at one of the primary 4 vendors and I really didn’t want to deal with duplicate kits any more than I already had to. Furthermore, GedMatch is undergoing a transition to their Genesis platform and matching within the Genesis framework has yet to be perfected for kits other than those from these vendors.

Let’s talk about working with matches from each vendor.


At Ancestry, make a list of all of your second and third cousin matches, plus as many 4th cousins as you want to work with.

To begin viewing your common matches, select your first second cousin on the list and click on the green View Match. (Note that I am using my own second kit at Ancestry, RobertaV2Estes, not a cousin’s kit in these examples. The methodology is the same, so don’t fret about that.)

Then, click on Shared Matches.

Referring to your spreadsheet, assign a color to this match group and color the spreadsheet squares for this match group. Looking at my spreadsheet, my first group would be the yellow Estes group, so I color the squares for each person that I match in common with this particular cousin. On my spreadsheet, those cousins have all been assigned pseudonyms, of course.

Your shared match list will be listed in highest match order which should be approximately the same order they are listed on your spreadsheet. I use two monitors so I can display the spreadsheet on one and the Ancestry match list on the other.

Lon is shared in common with the gold person I’m comparing against (Roberta V2 Estes), and me, so his box would be colored gold on the spreadsheet. Lon’s pseudonym is Sneezy and the person beneath him on this list, not shown, would be Ariel.

Ancestry only shows in-common matches to the 4th cousin level, so you really couldn’t reach deeper if you wanted. Furthermore, I can’t see any advantage to working beyond the 4th cousin’s level, maximum. Your best matches are going to be the largest ones that reveal the most information and have the most matches, therefore allowing you to group the most people by color.

Unfortunately, Ancestry provides the total cMs and the number of segments, but not the largest matching segment.

One benefit of this methodology is that it’s fairly easy to group those pesky private matches like the last one on the master spreadsheet, Cersei, shown in red. You’ll at least know which grandparent group they match. Based on your identified ancestors of matches in the color group, you may be able to tell much more about that private match.

For example, one of my private matches is a match to someone who I share great-great-grandparents with AND they also match with two people further on up that tree on the maternal side of that couple, shown above, in red. I may never know which ancestor I share with that private match specifically, but I have a pretty darned good idea now in spite of that ugly little lock. The more identified matches, the better and more accurate this technique.

Is the Leeds Method foolproof? No.

Is this a great tool? Yes, absolutely.

Family Tree DNA

Thankfully, Family Tree DNA provides more information about my matches than Ancestry, including segment information combined with a chromosome browser and Family Matching. I often refer to Family Matching as parental bucketing, shown on your match list with the maternal and paternal tabs, because Family Tree DNA separates your matches into parental “sides” based on common segments with others on your maternal and paternal branches of your tree when you link your matches’ results.

At Family Tree DNA, sign on and then click on Matches under Family Finder.

When viewing your matches, you’ll see blue or red people icons any that are assigned to either your maternal, paternal side, or both (purple) on your match list. If you click on the tabs at the top,  you’ll see JUST the maternal, paternal or both lists.

This combination of tools allows you to confirm (and often triangulate) the match for several people. If those matches are bucketed, meaning assigned to the same parental side, and they match on the same segment, they are triangulated for all intents and purposes if the segment is above 20 cM. All of the matches I worked with for the Leeds Method were well above 20 cM, so you don’t really need to worry about false or identical by chance matches at that level.

Family Tree DNA matches are initially displayed by the total number of “Shared cM.” Click on “Longest Block” to sort in that manner. I considered people through 30 cM and above as equivalent to the Ancestry 3rd cousin category. Some of the matching became inconsistent below that threshold.

List all of your second and third cousins on the spreadsheet, along with however many 4th cousins you want to work with.

Then, select your closest second cousin by checking the box to the left of that individual, then click on “In Common With” above the display. This shows you your matches in common with this person.

On the resulting common match list, sort your matches in Longest block order, then mark the matches on your spreadsheet in the correct colored columns.

With each vendor, you may need to make new columns until you can work with enough matches to figure out which column is which color – then you can transfer them over. If you’re lucky enough to already know the family association of your closest cousins, then you already know which colored column they belong to.

All of my matches that fell into the Leeds groups were previously bucketed to maternal or paternal, so consistency between the two confirms both methodologies. Between 20 and 28 cM, three of my bucketed matches at Family Tree DNA fell into another group using the Leeds method, which is why I drew the line at 30cM.

For genealogists who already know a lot about their tree, this methodology in essence divides the maternal and paternal buckets into half. FTDNA already assigns matches maternally or paternally with Family Matching if you have any information about how your matches fit into your tree and can link any matching testers to either side of your tree at the 3rd cousin level or closer.

If you don’t know anything about your heritage, or don’t have any way to link to other family members who have tested, you’ll start from scratch with the Leeds Method. If you can link family members, Family Tree DNA already does half of the heavy lifting for you which allows you to confirm the Leeds methodology.


At MyHeritage, sign in, click on DNA and sort by “largest segment,” shown at right, above. I didn’t utilize matches below 40 cM due to consistency issues. I wonder if imputation affects smaller matches more than larger matches.

You’ll see your closest matches at the top of the page. Scroll down and make a list on your spreadsheet of your second and third cousins. Return to your closest DNA match that is a second cousin and click on the purple “Review DNA Match” which will display your closest in-common matches with that person, but not necessarily in segment size order.

Scroll down to view the various matches and record on the spreadsheet in their proper column by coloring that space.

The great aspect of MyHeritage is that triangulation is built in, and you can easily see which matches triangulate, providing another layer of confirmation, assuming you know the relationship of at least some of your matches.

The message for me personally at MyHeritage is that I need to ask known cousins who are matches elsewhere to upload to MyHeritage because I can use those as a measuring stick to group matches, given that I know the cousin’s genealogy hands-down.

The great thing about MyHeritage is that they are focused on Europe, and I’m seeing European matches that aren’t anyplace else.


At 23andMe, sign in and click on DNA Relatives under the Ancestry tab.

You’ll see your list of DNA matches. Record 2nd and third cousins on your spreadsheet, as before.

To see who you share in common with a match, click on the person’s name and color your matches on the spreadsheet in the proper column.

Unfortunately, the Leeds Method simply didn’t work well for me with my 23andMe data, or at least the results are highly suspect and I have no way of confirming accuracy.

Most of my matches fell into in the Estes category, with the Boltons overlapping almost entirely, and none in the Lore or Ferverda columns. There is one small group that I can’t identify. Without trees or surnames, genealogically, my hands are pretty much tied. I can’t really explain why this worked so poorly at 23andMe. Your experience may be different.

The lack of trees is a significant detriment at 23andMe because other than a very few matches whose genealogy I know, there’s no way to correlate or confirm accuracy. My cousins who tested at 23andMe years ago and whose tests I paid for lost interest and never signed in to re-authorize matching. Many of those tests are on the missing Ferverda side, but their usefulness is now forever lost to me.

23andMe frustrates me terribly. Their lack of commitment to and investment in the genealogical community makes working with their results much more difficult than it needs to be. I’ve pretty much given up on using 23andMe for anything except adoption searches for very close matches as a last resort, and ethnicity.

The good news is that with so many people testing elsewhere, there’s a lot of good data just waiting!

What are the Benefits?

The perception of “benefit” is probably directly connected to your goal for DNA testing and genetic genealogy.

  • For adoptees or people seeking unknown parentage or unknown grandparents, the Leeds Method is a fantastic tool, paving the way to search for common surnames within the 4 groups as opposed to one big pool.
  • For people who have been working with their genealogy for a long time, maybe not as much, but hints may lurk and you won’t know unless you do the discovery work. If you’re a long-time genealogist, you’re used to this, so it’s just a new way of digging through records – and you can do it at home!
  • For people who have tested at Family Tree DNA, the family grouping by maternal and paternal based on people linked to your tree is more accurate and groups people further down your match list because it’s actually based on triangulated matching segments. However, the Leeds Method expands on that and adds granularity by breaking those two groups into four.
  • For people who want to paint their chromosomes using DNAPainter, the Leeds Method is the first step of a wonderful opportunity if you have tested at either Family Tree DNA, MyHeritage or 23andMe.

Unfortunately, Ancestry doesn’t provide segment information, so you can’t chromosome paint from Ancestry directly, BUT, you can upload to either Family Tree DNA, MyHeritage or GedMatch and paint Ancestry matches from there. At GedMatch, their kit numbers begin with A.

What Did I Do Differently than Dana?

Instead of adding a 5th column with the first person (Sam) who was not grouped into the first 4 groups, I looked for the closest matches that I shared with Sam who were indeed in the first 4 color groups. I added Sam to that existing color group along with my shared matches with Sam that weren’t already grouped into that color so long as it was relatively consistent. If it looked too messy, meaning I found people in multiple match groups, I left it blank or set that match aside. This didn’t happen until I was working at the 4th cousin level or between 30 and 40 cM, depending on the vendor.

Please note that just because you find people that you match in common with someone does NOT MEAN that you all share a common ancestor, or the same ancestor. It’s a hint, a tip to be followed.

There were a couple of groups that I couldn’t cluster with other groups, and one match that clustered in three of the four grandparent groups. I set that one aside as an outlier. I will attempt to contact them. They don’t have a tree.

I grouped every person through third cousin matches. I started out manually adding the 4th cousins for each match, but soon gave up on that due to the sheer magnitude. I did group my closest 4th cousins, or until they began to be inaccurate or messy, meaning matching in multiple groups. Second and third cousin matching was very consistent.


  • Don’t use siblings or anyone closer than the second cousin level. First cousins share two grandparents. You only want to use matches that can be assigned to ONLY ONE GRANDPARENT.
  • In the spreadsheet cell, mark the person you used as a “match to.” In other words, which people did you use to populate that color group. You can see that I used two different people in the Estes category. I used more in the other categories too, but they are further down in my list.
  • At Family Tree DNA, you can utilize the X chromosome. Understand that if you are a male, you will not have any X matches with your paternal grandfather. I would not recommend using X matches for the Leeds Method, especially since they are not uniformly available at all vendors and form a specific unique inheritance pattern that is not the same as the other autosomes.
  • Ancestry, MyHeritage and Family Tree DNA allow you to make notes on each match. As I group these, and as I paint them with DNAPainter I made a note on each match that allows me to identify which group they are assigned to, or if they match multiple groups.
  • Look at each match to be sure they are consistent. If they aren’t, either mark them as inconclusive or omit them entirely in the painting process. I write notes on each one if there is something odd, or if I don’t paint them.

What Did I Learn?

Almost all of my (endogamous by definition) Acadian matches are more distant, which means the segments are smaller. I expected to find more in the painted group, because I have SO MANY Acadian matches, but given that my closest Acadian ancestor was my great-great-grandfather, those segments are now small enough that those matches don’t appear in the candidate group of matches for the Leeds Method. My Acadian heritage occurs in my green Lore line, and there are surprisingly few matches in that grouping large or strong enough to show up in my clustered matches. In part, that’s probably because my other set of great-great-grandparents in that line arrived in 1852 from Germany and there are very few people in the US descended from them.

I found 4th cousin matches I would have otherwise never noticed because they don’t have a tree attached. At Ancestry, I only pay attention to closer matches, Shared Ancestor Hints and people with trees. We have so many matches today that I tend to ignore the rest.

Based on the person’s surname and the color group into which they fall, it’s often possible to assign them to a probable ancestral group based on the most distant ancestors of the people they match within the color group. In some cases, the surname is another piece of evidence and may provide a Y DNA lead.

For example, one of my matches user name is XXXFervida. They do match in the Ferverda grandparent group, and Fervida is how one specific line of the family spelled the surname. Of course, I could have determined that without grouping, but you can never presume a specific connection based solely on surname, especially with a more common name. For all I know, Fervida could be a married name.

By far the majority of my matches don’t have trees or have very small trees. That “no-tree” percentage is steadily increasing at Ancestry, probably due to their advertising push for ethnicity testing. At Family Tree DNA where trees are infinitely more useful, the percentage of people WITH trees is actually rising. By and large, Family Tree DNA users tend to be the more serious genealogists.

MyHeritage launched their product more recently with DNA plus trees from the beginning, although many of the new transfers don’t have trees or have private trees. Their customers seem to be genealogically savvy and many live in Europe where MyHeritage DNA testing is focused.

23andMe is unquestionably the least useful for the Leeds Method because of their lack of support for trees, among other issues, but you may still find some gems there.

Keeping Current

Now that I invested in all of this work, how will I keep the spreadsheet current, or will I at all?

At Ancestry, I plan to periodically map all of my SAH (Shared Ancestor Hints) green leaf matches as well as all new second and third cousin matches, trees or not.

In essence, for those with DNA matches and trees with a common ancestor, Ancestry already provides Circles, so they are doing the grouping for those people. Where this falls short, of course, is matches without trees and without a common identified ancestor.

For Ancestry matches, I would be better served, I think, to utilize Ancestry matches at GedMatch instead of at Ancestry, because GedMatch provides segment information which means the matches can be confirmed and triangulated, and can be painted.

For matches outside of Ancestry, in particular at Family Tree DNA and MyHeritage I will keep the spreadsheet current at least until I manage to paint my entire set of chromosomes. That will probably be a very long time!

I may not bother with 23andMe directly, given that I have almost no ability to confirm accuracy. I will utilize 23andMe matches at GedMatch. People who transfer to GedMatch tend to be interested in genealogy.

What Else Can I Do?

At Ancestry, I can use Blaine’s new “DNA Match Labeling” tool that facilitates adding 8 colored tags to sort matches at Ancestry. Think of it as organizing your closet of matches. I could tag each of these matches to their grandparent side which would make them easy to quickly identify by this “Leeds Tag.”

My Goals

I have two primary goals:

  • Associating segments of my DNA with specific ancestors
  • Breaking down genealogical brick walls

I want to map my DNA segments to specific ancestors. I am already doing this using Family Tree DNA and MyHeritage where common ancestors are indicated in trees and by surnames. I can map these additional Leeds leads (pardon the pun) to grandparents utilizing this methodology.

To the extent I can identify paternal and maternal matches at 23andMe, I can do the same thing. I don’t have either parents’ DNA there, and few known relatives, so separating matches into maternal and paternal is more difficult. It’s not impossible but it means I can associate fewer matches with “sides” of my genealogy.

For associating segments with specific ancestors and painting my chromosomes, DNAPainter is my favorite tool.

In my next article, we’ll see how to use our Leeds Method results successfully with DNAPainter and how to interpret the results.



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A Study Utilizing Small Segment Matching

There has been quite a bit of discussion in the last several weeks, both pro and con, about how to use small matching DNA segments in genetic genealogy.  A couple of people are even of the opinion that small segments can’t be used at all, ever.  Others are less certain and many of us are working our way through various scenarios.  Evidence certainly exists that these segments can be utilized.

I’ve been writing foundation articles, in preparation for this article, for several weeks now.  Recently, I wrote about how phasing works and determining IBD versus IBS matches and included guidelines for telling the difference between the different kinds of matches.  If you haven’t read that article, it’s essential to understanding this article, so now would be a good time to read or review that article.

I followed that with a step by step article, Demystifying Autosomal DNA Matching, on how to do phasing and matching in combination with the guidelines about how to determine IBD (identical by descent) versus IBS (identical by chance) and identical by population matches when evaluating your own matches.

Now that we understand IBS, IBD, Phasing and how matching actually works on a case by case basis, let’s look at applying those same matching and IBS vs IBD guidelines to small data segments as well.

A Little History

So those of you who haven’t been following the discussion on various blogs and social media don’t feel like you’ve been dropped into the middle of a conversation with no context, let me catch you up.

On Thanksgiving Day, I published an article about identifying one of my ancestors, after many years of trying, Sarah Hickerson.

That article spurred debate, which is just fine when the debate is about the science, but it subsequently devolved into something less pleasant.  There are some individuals with very strong opinions that utilizing small segments of DNA data can “never be done.”

I do not agree with that position.  In fact, I strongly disagree and there are multiple cases with evidence to support small segments being both accurate and useful in specific types of genealogical situations.  We’ll take a look at several.

I do agree that looking at small segment data out of context is useless.  To the best of my knowledge, no genealogist begins with their smallest segments and tries to assemble them, working from the bottom up.  We all begin with the largest segments, because they are the most useful and the closest connections in our tree, and work our way down.  Generally, we only work with small segments when we have to – and there are times that’s all we have.  So we need to establish guidelines and ways to know if those small segments are reliable or not.  In other words, how can we draw conclusions and how much confidence can we put in those conclusions?

Ultimately, whether you choose to use or work with small segment data will be your own decision, based on your own circumstances.  I simply wanted to understand what is possible and what is reasonable, both for my own genealogy and for my readers.

In my projects, I haven’t been using small segment data out of context, or randomly.  In other words, I don’t just pick any two small segment matches and infer or decide that they are valid matches.  Fortunately, by utilizing the IBD vs IBS guidelines, we have tools to differentiate IBD (Identical by Descent) segments from IBS (Identical by State) by chance segments and IBD/IBS by population for matching segments, both large and small.

Studying small segment data is the key to determining exactly how small segments can reasonably be utilized.  This topic probably isn’t black or white, but shades of gray – and assuming the position that something can’t be done simply assures that it won’t be.

I would strongly encourage those involved and interested in this type of research to retain those small segments, work with them and begin to look for patterns.  The only way we, as a community, are ever going to figure out how to work with small segments successfully and reliably is to, well, work with them.

Discussing the science and scenarios surrounding the usage of small data segments in various different situations is critical to seeing our way through the forest.  If the answers were cast in concrete about how to do this, we wouldn’t be working through this publicly today.

Negative personal comments and inferences have no place in the scientific community.  It discourages others from participating, and serves to stifle research and cooperation, not encourage it.  I hope that civil scientific discussions and comparisons involving small segment data can move forward, with decorum, because they are critically needed in order to enhance our understanding, under varying circumstances, of how to utilize small segment data.  As Judy Russell said, disagreeing doesn’t have to be disagreeable.

Two bloggers, Blaine Bettinger and CeCe Moore wrote articles following my Hickerson article.  Blaine subsequently wrote a second article here.  Felix Immanuel wrote articles here and here.

A few others have weighed in, in writing, as well although most commentary has been on Facebook.  Israel Pickholtz, a professional genealogist and genetic consultant, stated on his blog, All My Foreparents, the following:

It is my nature to distrust rules that put everything into a single category and that’s how I feel about small segments. Sometimes they are meaningful and useful, sometimes not.

When I reconstructed my father’s DNA using Lazerus (described last week in Genes From My Father), I happily accepted all small segments of whatever size because those small segments were in the DNA of at least one of his children and at least one of his brother/sister/first cousin. If I have a particular small segment, I must have received it from my parents. If my father’s brother (or sister) has it as well, then it is eminently clear to me that I got it from my father and that it came to him and his brother from my grandfather. And it is not reasonable to say that a sliver of that small segment might have come from my mother, because my father’s people share it.

After seeing Israel’s commentary about Lazarus, I reconstructed the genome of both Roscoe and John Ferverda, brothers, which includes both large and small segments.  Working with the Ferverda DNA further, I wrote an article, Just One Cousin, about matching between two siblings and a first cousin, which includes lots of small data segments, some of which were proven to triangulate, meaning they are genuine, and some which did not.  There are lots more examples in the demystifying article, as well.

What Not To Do 

Before we begin, I want to make it very clear that am not now, and never have, advocated that people utilize small data segments out of context of larger matching segments and/or at least suspected matching genealogy.  For example, I have never implied or even hinted that anyone should go to GedMatch, do a “one to many” compare at 1 cM and then contact people informing them that they are related.  Anyone who has extrapolated what I’ve written to mean that either simply did not understand or intentionally misinterpreted the articles.

Sarah Hickerson Revisited

If I thought Sarah Hickerson caused me a lot of heartburn in the decades before I found her, little did I know how much heartburn that discovery would cause.

Let’s go back to the Sarah Hickerson article that started the uproar over whether small data segments are useful at all.

In that article, I found I was a member of a new Ancestry DNA Circle for Charles Hickerson and Mary Lytle, the parents of Sarah Hickerson.

Ancestry Hickerson match

Because there are no tools at Ancestry to prove DNA connections, I hurried over to Family Tree DNA looking for any matches to Hickersons for myself and for my Vannoy cousins who also (potentially) descended from this couple.  Much to my delight, I found  several matches to Hickersons, in fact, more than 20 – a total of 614 rows of spreadsheet matches when I included all of my Vannoy cousins who potentially descend from this couple to their Hickerson matches.  There were 64 matching clusters of segments, both small and large.  Some matches were as large as 20cM with 6000 SNPs and more than 20 were over 10cM with from 1500 to 6000 SNPs.  There were also hundreds of small segments that matched (and triangulated) as well.

By the time I added in a few more Vannoy cousins that we’ve since recruited, the spreadsheet is now up to 1093 rows and we have 52 Vannoy-Hickerson TRIANGULATED CLUSTERS utilizing only Family Tree DNA tools.

Triangulated DNA, found in 3 or more people at the same location who share a common ancestor is proven to be from that ancestor (or ancestral couple.)  This is the commonly accepted gold standard of autosomal DNA triangulation within the industry.

Here’s just one example of a cluster of three people.  Charlene and Buster are known (proven, triangulated) cousins and Barbara is a descendant of Charles Hickerson and Mary Lytle.

example triang

What more could you want?

Yes, I called this a match.  As far as I’m concerned, it’s a confirmed ancestor.  How much more confirmed can you get?

Some clusters have as many as 25 confirmed triangulated members.

chr 13 group

Others took issue with this conclusion because it included small segment data.  This seems like the perfect opportunity in which to take a look at how small segments do, or don’t stand up to scrutiny.  So, let’s do just that.  I also did the same type of matching comparison in a situation with 2 siblings and a known cousin, here.

To Trash…or Not To Trash

Some genetic genealogists discard small segments entirely, generally under either 5 or 7cM, which I find unfortunate for several reasons.

  1. If a person doesn’t work with small segments, they really can’t comment on the lack of results, and they’ll never have a success because the small segments will have been discarded.
  2. If a person doesn’t work with small segments, they will never notice any trends or matches that may have implications for their ancestry.
  3. If a person doesn’t work with small segments, they can’t contribute to the body of evidence for how to reasonably utilize these segments.
  4. If a person doesn’t work with small segments, they may well be throwing the baby out with the bathwater, but they’ll never know.
  5. They encourage others to do the same.

The Sarah Hickerson article was not meant as a proof article for anything – it was meant to be an article encouraging people to utilize genetic genealogy for not only finding their ancestor and proving known connections, but breaking down brick walls.  It was pointing the way to how I found Sarah Hickerson.  It was one of my 52 Ancestors Series, documenting my ancestors, not one of the specifically educational articles.  This article is different.

If you are only interested in the low hanging fruit, meaning within the past 5 or 6 generations, and only proving your known pedigree, not finding new ancestors beyond that 5-6 generation level, then you can just stop reading now – and you can throw away your small segments.  But if you want more, then keep reading, because we as a community need to work with small segment data in order to establish guidelines that work relative to utilizing small segments and identifying the small segments that can be useful, versus the ones that aren’t.

I do not believe for one minute that small segments are universally useless.  As Israel said, if his family did not receive those segments from a common family member, then where did they all get those matching segments?

In fact, utilizing triangulated and proven DNA relationships within families is how adoptees piece together their family trees, piggybacking off of the work of people with known pedigrees that they match genetically.  My assumption had been that the adoptee community utilized only large DNA segments, because the larger the matching segments, generally the closer in time the genealogy match – and theoretically the easier to find.

However, I discovered that I was wrong, and the adoptee community does in fact utilize small segments as well.  Here’s one of the comments posted on my Chromosome Browser War blog article.

“Thanks for the well thought out article, Roberta, I have something to add from the folks at DNAadoption. Adoptees are not just interested in the large segments, the small segments also build the proof of the numerous lines involved. In addition, the accumulation of surnames from all the matches provides a way to evaluate new lines that join into the tree.”

Diane Harman-Hoog (on behalf of the 6 million adoptees in this country, many of who are looking for information on medical records and family heritage).

Diane isn’t the only person who is working with small segment data.  Tim Janzen works with small segments, in particular on his Mennonite project, and discusses small segments on the ISOGG WIKI Phasing page.  Here is what Tim has to say:

“One advantage of Family Finder is that FF has a 1 cM threshold for matching segments. If a parent and a child both have a matching segment that is in the 2 to 5 cM range and if the number of matching SNPs is 500 or more then there is a reasonably high likelihood that the matching segment is IBD (identical by descent) and not IBS (identical by state).”

The same rules for utilizing larger segment data need to be applied to small segment data to begin with.

Are more guidelines needed for small segments?  I don’t know, but we’ll never know if we don’t work with many individual situations and find the common methods for success and identify any problematic areas.

Why Do Small Segments Matter?

In some cases, especially as we work beyond the 6 generation level, small segments may be all we have left of a specific ancestor.  If we don’t learn to recognize and utilize the small segments available to us, those ancestors, genetically speaking, will be lost to us forever.

As we move back in time, the DNA from more distant ancestors will be divided into smaller and smaller segments, so if we ever want the ability to identify and track those segments back in time to a specific ancestor, we have to learn how to utilize small segment data – and if we have deleted that data, then we can’t use it.

In my case, I have identified all of my 5th generation ancestors except one, and I have a strong lead on her.  In my 6th generation, however, I have lots of walls that need to be broken through – and DNA may be the only way I’ll ever do that.

Let’s take a look at what I can expect when trying to match people who also descend from an ancestor 5 generations back in time.  If they are my same generation, they would be my fourth cousins.

Based on the autosomal statistics chart at ISOGG, 4th cousins, on the average, would expect to share about 13.28 cM of DNA from their common ancestor.  This would not be over the match threshold at FTDNA of approximately 20 cM total, and if those segments were broken into three pieces, for example, that cousin would not show as a match at either FTDNA or 23andMe, based on the vendors’ respective thresholds.

% Shared DNA Expected Shared cM Relationship
0.781% 53.13 Third cousins, common ancestor is 4 generations back in time
0.391% 26.56 Third cousins once removed
20 cm Family Tree DNA total cM Threshold
0.195% 13.28 Fourth cousins, common ancestor is 5 generations back in time
7 cM 23andMe individual segment cM match threshold
0.0977% 6.64 Fourth cousins once removed
0.0488% 3.32 Fifth cousins, common ancestor is 6 generations back in time
0.0244 1.66 Fifth cousins once removed

If you’re lucky, as I was with Hickerson, you’ll match at least some relative who carries that ancestral DNA line above the threshold, and then they’ll match other cousins above the threshold, and you can build a comparison network, linking people together, in that fashion.  And yes you may well have to utilize GedMatch for people testing at various different vendors and for those smaller segment comparisons.

For clarification, I have never “called” a genealogy match without supporting large segment data.  At the vendors, you can’t even see matches if they don’t have larger segments – so there is no way to even know you would match below the threshold.

I do think that we may be able to make calls based on small segments, at least in some instances, in the future.  In fact, we have to figure out how to do this or we will rarely be able to move past the 5th or 6th generation utilizing genetics.

At the 5th generation, or third cousins, one expects to see approximately 26 cM of matching DNA, still over the threshold (if divided correctly), but from that point further back in time, the expected shared amount of DNA is under the current day threshold.  For those who wonder why the vendors state that autosomal matches are reliable to about the 5th or 6th generation, this is the answer.

I do not discount small segments without cause.  In other words, I don’t discount small segments unless there is a reason.  Unless they are positively IBS by chance, meaning false, and I can prove it, I don’t disregard them.  I do label them and make appropriate notes.  You can’t learn from what’s not there.

Let me give you an example.  I have one area of my spreadsheet where I have a whole lot of segments, large and small, labeled Acadian.  Why?  Because the Acadians are so intermarried that I can’t begin to sort out the actual ancestor that DNA came from, at least not yet…so today, I just label them “Acadian.”

This example row is from my master spreadsheet.  I have my Mom’s results in my spreadsheet, so I can see easily if someone matches me and Mom both. My rows are pink.  The match is on Mom’s side, which I’ve color coded purple.  I don’t know which ancestor is the most recent common ancestor, but based on the surnames involved, I know they are Acadian.  In some cases, on Acadian matches, I can tell the MRCA and if so, that field is completed as well.

Me Mom acadian

As a note of interest, I inherited my mother’s segment intact, so there was no 50% division in this generation.

I also have segments labeled Mennonite and Brethren.  Perhaps in the future I’ll sort through these matches and actually be able to assign DNA segments to specific ancestors.  Those segments aren’t useless, they just aren’t yet fully analyzed.  As more people test, hopefully, patterns will emerge in many of these DNA groupings, both small and large.

In fact, I talked about DNA patterns and endogamous populations in my recent article, Just One Cousin.

For me, today, some small segment matches appear to be central European matches.  I say “appear to be,” because they are not triangulated.  For me this is rather boring and nondescript – but if this were my African American client who is trying to figure out which line her European ancestry came from, this could be very important.  Maybe she can map these segments to at least a specific ancestral line, which she would find very exciting.

Learning to use small segments effectively has the potential to benefit the following groups of people:

  • People with colonial ancestry, because all that may be left today of colonial ancestors is small segments.
  • People looking to break down brick walls, not just confirm currently known ancestors.
  • People looking for minority ancestors more than 5 or 6 generations back in their trees.
  • Adoptees – although very clearly, they want to work with the largest matches first.
  • People working with ethnic identification of ancestors, because you will eventually be able to track ethnicity identifying segments back in time to the originating ancestor(s).

Conversely, people from highly endogamous groups may not be helped much, if at all, by small segments because they are so likely to be widely shared within that population as a group from a common ancestor much further back in time.  In fact, the definition of a “small segment” for people with fully endogamous families might be much larger than for someone with no known endogamy.

However, if we can identify segments to specific populations, that may help the future accuracy of ethnicity testing.

Let’s go back and take a look at the Hickerson data using the same format we have been using for the comparisons so far.

Small Segment Examples

These Hickerson/Vannoy examples do not utilize random small segment matches, but are utilizing the same matching rules used for larger matches in conjunction with known, triangulated cousin groups from a known ancestor.  Many cousins, including 2 brothers and their uncle all carry this same DNA.  Like in Israel’s case, where did they get that same DNA if not from a common ancestor?

In the following examples, I want to stress that all of the people involved DO HAVE LARGER SEGMENT MATCHES on other chromosomes, which is how we knew they matched in the first place, so we aren’t trying to prove they are a match.  We know they are.  Our goal is to determine if small segments are useful in the same situation, proving matches, as with larger segments.  In other words, do the rules hold true?  And how do we work with the data?  Could we utilize these small segment matches if we didn’t have larger matching segments, and if so, how reliable would they be?

There is a difference between a single match and a triangulated group:

  • Matches between two people are suggestive of a common ancestor but could be IBS by chance or population..
  • Multiple matches, such as with the 6 different Hickersons who descend from Charles Hickerson and Mary Lytle, both in the Ancestry DNA Circle and at Family Tree DNA, are extremely suggestive of a specific common ancestor.
  • Only triangulated groups are proof of a common ancestor, unless the people are  closely related known relatives.

In our Hickerson/Vannoy study, all participants match at least to one other (but not to all other) group members at Family Tree DNA which means they match over the FTDNA threshold of approximately 20 cM total and at least one segment over 7.7cM and 500 SNPs or more.

In the example below, from the Hickerson article, the known Vannoy cousins are on the left side and the Hickerson matches to the Vannoy cousins are across the top.  We have several more now, but this gives you an idea of how the matching stacked up initially.  The two green individuals were proven descendants from Charles Hickerson and Mary Lytle.

vannoy hickerson higginson matrix

The goal here is to see how small data segments stack up in a situation where the relationship is distant.  Can small segments be utilized to prove triangulation?  This is slightly different than in the Just One Cousin article, where the relationship between the individuals was close and previously known.  We can contrast the results of that close relationship and small segments with this more distant connection and small segments.

Sarah Hickerson and Daniel Vannoy

The Vannoy project has a group of about a dozen cousins who descend from Elijah Vannoy who have worked together to discover the identify of Elijah’s parents.  Elijah’s father is one of 4 Vannoy men, all sons of the same man, found in Wilkes County, NC. in the late 1700s.  Elijah Vannoy is 5 generations upstream from me.

What kind of evidence do we have?  In the paper genealogy world, I have ruled out one candidate via a Bible record, and probably a second via census and tax records, but we have little information about the third and fourth candidates – in spite of thoroughly perusing all existent records.  So, if we’re ever going to solve the mystery, short of that much-wished-for Vannoy Bible showing up on e-Bay, it’s going to have to be via genetic genealogy.

In addition to the dozen or so Vannoy cousins who have DNA tested, we found 6 individuals who descend from Sarah Hickerson’s parents, Charles Hickerson and Mary Lytle who match various Vannoy cousins.  Additionally, those cousins match another 21 individuals who carry the Hickerson or derivative surnames, but since we have not proven their Hickerson lineage on paper, I have not utilized any of those additional matches in this analysis.  Of those 26 total matches, at Family Tree DNA, one Hickerson individual matches 3 Vannoy cousins, nine Hickerson descendants match 2 Vannoy cousins and sixteen Hickerson descendants match 1 Vannoy cousin.

Our group of Vannoy cousins matching to the 6 Charles Hickerson/Mary Lytle descendants contains over 60 different clusters of matching DNA data across the 22 chromosomes.  Those 6 individuals are included in 43 different triangulated groups, proving the entire triangulation group shares a common ancestor.  And that is BEFORE we add any GedMatch information.

If that sounds like a lot, it’s not.  Another recent article found 31 clusters among siblings and their first cousin, so 60 clusters among a dozen known Vannoy cousins and half a dozen potential Hickerson cousins isn’t unusual at all.

To be very clear, Sarah Hickerson and Daniel Vannoy were not “declared” to be the parents of Elijah Vannoy, born in 1784, based on small segment matches alone.  Larger segment matches were involved, which is how we saw the matches in the first place.  Furthermore, the matches triangulated.  However, small segments certainly are involved and are more prevalent, of course, than large segments.  Some cousins are only connected by small segments.  Are they valid, and how do we tell?  Sometimes it’s all we have.

Let me give you the classic example of when small segments are needed.

We have four people.  Person A and B are known Vannoy cousins and person C and D are potential Hickerson cousins.  Potential means, in this case, potential cousins to the Vannoys.  The Hickersons already know they both descend from Charles Hickerson and Mary Lytle.

  • Person A matches person C on chromosome 1 over the matching threshold.
  • Person B matches person D on chromosome 2 over the matching threshold.

Both Vannoy cousins match Hickerson cousins, but not the same cousin and not on the same segments at the vendor.  If these were same segment matches, there would be no question because they would be triangulated, but they aren’t.

So, what do we do?  We don’t have access to see if person C and D match each other, and even if we did, they don’t match on the same segments where they match persons A and B, because if they did we’d see them as a match too when we view A and B.

If person A and B don’t match each other at the vendor, we’re flat out of luck and have to move this entire operation to GedMatch, assuming all 4 people have or are willing to download their data.

a and b nomatch

If person A and B match each other at the vendor, we can see their small segment data as compared to each other and to persons C and D, respectively which then gives us the ability to see if A matches C on the same small segment as B matches D.

a and b match

If we are lucky, they will all show a common match on a small segment – meaning that A will match B on a small segment of chromosome 3, for example, and A will match C on that same segment.  In a perfect world, B will also match D on that same segment, and you will have 4 way triangulation – but I’m happy with the required 3 way match to triangulate.

This is exactly what happened in the article, Be Still My H(e)art.  As you can see, three people match on chromosomes 1 and 8, below – two of whom are proven cousins and the third was the wife surname candidate line.

Younger Hart 1-8

The example I showed of chromosome 2 in the Hickerson article was where all participants of the 5 individuals shown on the chromosome browser were matching to the Vannoy participant.  I thought it was a good visual example.  It was just one example of the 60+ clusters of cousin matches between the dozen Vannoy cousins and 6 Hickerson descendants.

This example was criticized by some because it was a small segment match.  I should probably have utilized chromosome 15 or searched for a better long segment example, but the point in my article was only to show how people that match stack up together on the chromosome browser – nothing more.   Here’s the entire chromosome, for clarity.

hickerson vannoy chr 2

Certainly, I don’t want to mislead anyone, including myself.  Furthermore, I dislike being publicly characterized as “wrong” and worse yet, labeled “irresponsible,” so I decided to delve into the depths of the data and work through several different examples to see if small segment data matching holds in various situations.  Let’s see what we found.

Chromosome 15

I selected chromosome 15 to work with because it is a region where a lot of Vannoy descendants match – and because it is a relatively large segment.  If the Hickersons do match the Vannoys, there’s a fairly good change they might match on at least part of that segment.  In other words, it appears to be my best bet due to sheer size and the number of Elijah Vannoy’s descendants who carry this segment.  In addition to the 6 individuals above who matched on chromosome 15, here are an additional 4.  As you can see, chromosome 15 has a lot of potential.

Chrom 15 Vannoy

The spreadsheet below shows the sections of chromosome 15 where cousins match.  Green individuals in the Match column are descendants of Charles Hickerson and Mary Lytle, the parents of Sarah Hickerson.  The balance are Vannoys who match on chromosome 15.

chr 15 matches ftdna v4

As you can see, there are several segments that are quite large, shown in yellow, but there are also many that are under the threshold of 7cM, which are all  segments that would be deleted if you are deleting small segments.  Please also note that if you were deleting small segments, all of the Hickerson matches would be gone from chromosome 15.

Those of you with an eagle eye will already notice that we have two separate segments that have triangulated between the Vannoy cousins and the Hickerson descendants, noted in the left column by yellow and beige.  So really, we could stop right here, because we’ve proven the relationship, but there’s a lot more to learn, so let’s go on.

You Can’t Use What You Can’t See

I need to point something out at this point that is extremely important.

The only reason we see any segment data below the match threshold is because once you match someone on a larger segment at Family Tree DNA, over the threshold, you also get to view the small segment data down to 1cM for your match with that person. 

What this means is that if one person or two people match a Hickerson descendant, for example you will see the small segment data for their individual matches, but not for anyone that doesn’t match the participant over the matching threshold.

What that means in the spreadsheet above, is that the only Hickerson that matches more than one Vannoy (on this segment) is Barbara – so we can see her segment data (down to 1cM ) as compared to Polly and Buster, but not to anyone else.

If we could see the smaller segment data of the other participants as compared to the Hickerson participants, even though they don’t match on a larger segment over the matching threshold, there could potentially be a lot of small segment data that would match – and therefore triangulate on this segment.

This is the perfect example of why I’ve suggested to Family Tree DNA that within projects or in individuals situations, that we be allowed to reduce the match threshold – especially when a specific family line match is suspected.

This is also one of the reasons why people turn to GedMatch, and we’ll do that as well.

What this means, relative to the spreadsheet is that it is, unfortunately, woefully incomplete – and it’s not apples to apples because in some cases we have data under the match threshold, and in some, we don’t.  So, matches DO count, but nonmatches where small segment data is not available do NOT count as a non-match, or as disproof.  It’s only negative proof IF you have the data AND it doesn’t match.

The Vannoys match and triangulate on many segments, so those are irrelevant to this discussion other than when they match to Hickerson DNA.  William (H), descends from two sons of Charles Hickerson and Mary Lytle.  Unfortunately, he only matches one Vannoy, so we can only see his small segments for that one Vannoy individual, William (V).  We don’t know what we are missing as compared to the rest of the Vannoy cousins.

To see William (H)’s and William (V)’s DNA as compared to the rest of the Vannoy cousins, we had to move to GedMatch.

Matching Options

Since we are working with segments that are proven to be Vannoy, and we are trying to prove/disprove if Daniel Vannoy and Sarah Hickerson are the parents of Elijah through multiple Hickerson matches, there are only a few matching options, which are:

  1. The Hickerson individuals will not triangulate with any of the Vannoy DNA, on chromosome 15 or on other chromosomes, meaning that Sarah Hickerson is probably not the mother of Elijah Vannoy, or the common ancestor is too far back in time to discern that match at vendor thresholds.
  2. The Hickerson individuals will not triangulate on this segment, but do triangulate on other segments, meaning that this segment came entirely from the Vannoy side of the family and not the Hickerson side of the family. Therefore, if chromosome 15 does not triangulate, we need to look at other chromosomes.
  3. The Hickerson individuals triangulate with the Vannoy individuals, confirming that Sarah Hickerson is the mother of Elijah Vannoy, or that there is a different common unknown ancestor someplace upstream of several Hickersons and Vannoys.

All of the Vannoy cousins descend from Elijah Vannoy and Lois McNiel, except one, William (V), who descends from the proven son of Sarah Hickerson and Daniel Vannoy, so he would be expected to match at least some Hickerson descendants.  The 6 Hickerson cousins descend from Charles Hickerson and Mary Lytle, Sarah’s parents.

hickerson vannoy pedigree

William (H), the Hickerson cousin who descends from David, brother to Sarah Hickerson, is descended through two of David Hickerson’s sons.

I decided to utilize the same segment “mapping comparison” technique with a spreadsheet that I utilized in the phasing article, because it’s easy to see and visualize.

I have created a matching spreadsheet and labeled the locations on the spreadsheet from 25-100 based on the beginning of the start location of the cluster of matches and the end location of the cluster.

Each individual being compared on the spreadsheet below has a column across the top.  On the chart below, all Hickerson individuals are to the right and are shown with their cells highlighted yellow in the top row.

Below, the entire colorized chart of chromosome 15 is shown, beginning with location 25 and ending with 100, in the left hand column, the area of the Vannoy overlap.  Remember, you can double click on the graphics to enlarge.  The columns in this spreadsheet are not fully expanded below, but they are in the individual examples.

entire chr 15 match ss v4

I am going to step through this spreadsheet, and point out several aspects.

First, I selected Buster, the individual in the group to begin the comparison, because he was one of the closest to the common ancestor, Elijah Vannoy, genealogically, at 4 generations.  So he is the person at Family Tree DNA that everyone is initially compared against.

Everyone who matches Buster has their matching segments shown in blue.  Buster is shown furthest left.

When participants match someone other than Buster, who they match on that segment is typed into their column.  You can tell who Buster matches because their columns are blue on matching locations.  Here’s an example.

Me Buster match

You can see that in my column, it’s blue on all segments which means I match Buster on this entire region.  In addition, there are names of Carl, Dean, William Gedmatch and Billie Gedmatch typed into the cell in the first row which means at that location, in addition to Buster, I also match Carl and Dean at Family Tree DNA and William (descended from the son of Daniel Vannoy and Sarah Hickerson) at Gedmatch and Billie (a Hickerson) at Gedmatch.  Their name is typed into my column, and mine into theirs.  Please note that I did not run everyone against everyone at GedMatch.  I only needed enough data to prove the point and running many comparisons is a long, arduous process even when GedMatch isn’t experiencing problems.

On cells that aren’t colorized blue, the person doesn’t match Buster, but may still match other Vannoy cousin segments.  For example, Dean, below, matches Buster on location 25-29, along with some other cousins.  However, he does not match Buster on location 30 where he instead matches Harold and Carl who also don’t match Buster at that location. Harold, Carl and Dean do, however, all descend from the same son of Elijah so they may well be sharing DNA from a Vannoy wife at this location, especially since no one who doesn’t share that specific wife’s line matches those three at this location.

Me Buster Dean match

Remember, we are not working with random small data segments, but with a proven matching segment to a common Vannoy ancestor, with a group of descendants from a possible/probable Hickerson ancestor that we are trying to prove/disprove.  In other words, you would expect either a lot of Hickerson matches on the same segments, if Hickerson is indeed a Vannoy ancestral family, or virtually none of them to match, if not.

The next thing I’d like to point out is that these are small segments of people who also have larger matching segments, many of whom do triangulate on larger segments on other chromosomes.  What we are trying to discern is whether small segment matches can be utilized by employing the same matching criteria as large segment matching.  In other words, is small segment data valid and useful if it meets the criteria for an IBD match?

For example, let’s look at Daniel.  Daniel’s segments on chromosome 15, were it not for the fact that he matches on larger segments on other chromosomes, would not be shown as matches, because they are not individually over the match threshold.

Look at Daniel’s column for Polly and Warren.

Daniel matches 2

The segments in red show a triangulated group where Daniel and Warren, or Daniel, Warren and Polly match.  The segments where all 3 match are triangulated.

This proves, unquestionably, that small segments DO match utilizing the normal prescribed IBD matching criteria.  This spreadsheet, just for chromosome 15, is full of these examples.

Is there any reason to think that these triangulated matches are not identical by descent?  If they are not IBD, how do all of these people match the same DNA? Chance alone?  How would that be possible?  Two people, yes, maybe, but 3 or more?  In some cases, 5 or 6 on the same segment?  That is simply not possible, or we have disproven the entire foundation that autosomal DNA matching is based upon.

The question will soon be asked if small segments that triangulate can be useful when there are no larger matching segments to put the match over the initial vendor threshold.

Triangulated Groups

As you can see, most of the people and segments on the spreadsheet, certainly the Elijah descendants, are heavily triangulated, meaning that three or more people match each other on the same locations.  Most of this matching is over the vendor threshold at Family Tree DNA.

You can see that Buster, Me, Dean, Carl and Harold all match each other on the same segments, on the left half of the spreadsheet where our names are in each other’s columns.

triangulated groups

Remember when I said that the spreadsheet was incomplete?  This is an example.  David and Warren don’t match each other at a high enough total of segments to get them over the matching threshold when compared to each other, so we can’t see their small segment data as compared to each other.  David matches Buster, but Warren doesn’t, so I can’t even see them both in relationship to a common match.  There are several people who fall into this category.

Let’s select one individual to use as an example.

I’ve chosen the Vannoy cousin, William(V), because his kit has been uploaded to Gedmatch, he has Vannoy matches and because William is proven to descend from Sarah Hickerson and Daniel Vannoy through their son Joel – so we expect some Hickerson DNA to match William(V).

If William (V) matches the Hickersons on the same DNA locations as he matches to Elijah’s descendants, then that proves that Elijah’s descendant’s DNA in that location is Hickerson DNA.

At GedMatch, I compared William(V) with me and then with Dean using a “one to one” comparison at a low threshold, simply because I wanted as much data as I could get.  Family Tree DNA allows for 1 cM and I did the same, allowing 100 SNPs at GedMatch.  Family Tree DNA’s lowest SNP threshold is 500.

In case you were wondering, even though I did lower the GedMatch threshold below the FTDNA minimum, there were 45 segments that were above 1cM and above 500 SNPs when matching me to William(V), which would have been above the lowest match threshold at FTDNA (assuming we were over the initial match threshold.)  In other words, had we not been below the original match threshold (20cM total, one segment over 7.7cM), these segments would have been included at FTDNA as small segments.  As you can see in the chart below, many triangulated.

I colorized the GedMatch matches, where there were no FTDNA matches, in dark red text.  This illustrates graphically just how much is missed when the small segments are ignored in cases with known or probable cousins.  In the green area, the entry that says “Me GedMatch” could not be colorized red (because you can’t colorize only part of the text of a cell) so I added the Gedmatch designation to differentiate between a match through FTDNA and one from GedMatch.  I did the same with all Gedmatch matches, whether colorized or not.

Let’s take a look and see how small segments from GedMatch affect our Hickerson matching.  Note that in the green area, William (V) matches William (H), the Hickerson descendant, and William (V) matches to me and Dean as well.  This triangulates William (V)’s Hickerson DNA and proves that Elijah’s descendants DNA includes proven Hickerson segments.

William (V) gedmatch matches v2

In this next example, I matched William (H), the Hickerson cousin (with no Vannoy heritage) against both Buster and me.

William (H) gedmatch me buster

Without Gedmatch data, only two segments of chromosome 15 are triangulated between Vannoy and Hickerson cousins, because we can’t see the small data segments of the rest of the cousins who don’t match over the threshold.

You can see here that nearly the entire chromosome is triangulated using small segments.  In the chart below, you can see both William(V) and William (H) as they match various Vannoy cousins.  Both triangulate with me.

William V and William H

I did the same thing with the Hickerson descendant, Billie, as compared to both me and Dean, with the same type of results.

The next question would be if chromosome 15 is a pileup area where I have a lot of IBS matches that are really population based matches.  It does not appear to be.  I have identified an area of my chromosomes that may be a pileup area, but chromosome 15 does not carry any of those characteristics.

So by utilizing the small segments at GedMatch for chromosome 15 that we can’t otherwise see, we can triangulate at least some of the Hickerson matches.  I can’t complete this chart, because several individuals have not uploaded to GedMatch.

Why would the Hickerson descendant match so many of the Vannoy segments on chromosome 15?  Because this is not a random sample.  This is a proven Vannoy segment and we are trying to see which parts of this segment are from a potential Hickerson mother or the Vannoy father.  If from the Hickerson mother, then this level of matching is not unexpected.  In fact, it would be expected.  Since we cheated and saw that chromosome 15 was already triangulated at Family Tree DNA, we already knew what to expect.

In the spreadsheet below, I’ve added the 2 GedMatch comparisons, William (V) to me and Dean, and William (H) to me and Buster.  You can see the segments that triangulate, on the left.  We could also build “triangulated groups,” like GedMatch does.  I started to do this, but then stopped because I realized most cells would be colored and you’d have a hard time seeing the individual triangulated segments.  I shifted to triangulating only the individuals who triangulate directly with the Hickerson descendant, William(H), shown in green.  GedMatch data is shown in red.

chr 15 with gedmatch

I would like to make three points.

1.  This still is not a complete spreadsheet where everyone is compared to everyone.  This was selectively compared for two known Hickerson cousins, William (V) who descends from both Vannoys and Hickersos and William (H) who descends only from Hickersons.

2. There are 25 individually triangulated segments to the Hickerson descendant on just this chromosome to the various Vannoy cousins.  That’s proof times 25 to just one Hickerson cousin.

3.  I would NEVER suggest that you select one set of small segments and base a decision on that alone.  This entire exercise has assembled cumulative evidence.  By the same token, if the rules for segment matching hold up under the worst circumstances, where we have an unknown but suspected relationship and the small segments appear to continue to follow the triangulation rules, they could be expected to remain true in much more favorable circumstances.

Might any of these people have random DNA matches that are truly IBS by chance on chromosome 15?  Of course, but the matching rules, just like for larger segments, eliminates them.  According to triangulation rules, if they are IBS by chance, they won’t triangulate.  If they do triangulate, that would confirm that they received the same DNA from a common ancestor.

If this is not true, and they did not receive their common DNA from a common ancestor, then it disproves the fundamental matching rule upon which all autosomal DNA genetic genealogy is based and we all need to throw in the towel and just go and do something else.

Is there some grey area someplace?  I would presume so,  but at this point, I don’t know how to discern or define it, if there is.  I’ve done three in-depth studies on three different families over the past 6 weeks or so, and I’ve yet to find an area (except for endogamous populations that have matches by population) where the guidelines are problematic.  Other researchers may certainly make different discoveries as they do the same kind of studies.  There is always more to be discovered, so we need to keep an open mind.

In this situation, it helps a lot that the Hickerson/Vannoy descendants match and triangulate on larger segments on other chromosomes.  This study was specifically to see if smaller segments would triangulate and obey the rules. We were fortunate to have such a large, apparently “sticky” segment of Vannoy DNA on chromosome 15 to work with.

Does small segment matching matter in most cases, especially when you have larger segments to utilize?  Probably not. Use the largest segments first.  But in some cases, like where you are trying to prove an ancestor who was born in the 1700s, you may desperately need that small segment data in order to triangulate between three people.

Why is this important – critically important?  Because if small segments obey all of the triangulation rules when larger segments are available to “prove” the match, then there is no reason that they couldn’t be utilized, using the same rules of IBD/IBS, when larger segments are not available.  We saw this in Just One Cousin as well.

However, in terms of proof of concept, I don’t know what better proof could possibly be offered, within the standard genetic genealogy proofs where IBD/IBS guidelines are utilized as described in the Phasing article.  Additional examples of small segment proof by triangulation are offered in Just One Cousin, Lazarus – Putting Humpty Dumpty Together Again, and in Demystifying Autosomal DNA Matching.

Raising Elijah Vannoy and Sarah Hickerson from the Dead

As I thought more about this situation, I realized that I was doing an awful lot of spreadsheet heavy lifting when a tool might already be available.  In fact, Israel’s mention of Lazarus made me wonder if there was a way to apply this tool to the situation at hand.

I decided to take a look at the Lazarus tool and here is what the intro said:

Generate ‘pseudo-DNA kits’ based on segments in common with your matches. These ‘pseudo-DNA kits’ can then be used as a surrogate for a common ancestor in other tests on this site. Segments are included for every combination where a match occurs between a kit in group1 and group2.

It’s obvious from further instructions that this is really meant for a parent or grandparent, but the technique should work just the same for more distant relatives.

I decided to try it first just with the descendants of Elijah Vannoy.  At first, I thought that recreated Elijah would include the following DNA:

  • DNA segments from Elijah Vannoy
  • DNA segments from Elijah Vannoy’s wife, Lois McNiel
  • DNA segments that match from Elijah’s descendants spouse’s lines when individuals come from the same descendant line. This means that if three people descend from Joel Vannoy and Phoebe Crumley, Elijah’s son and his wife, that they would match on some DNA from Phoebe, and that there was no way to subtract Phoebe’s DNA.

After working with the Lazarus tool, I realized this is not the case because Lazarus is designed to utilize a group of direct descendants and then compare the DNA of that group to a second group of know relatives, but not descendants.

In other words, if you have a grandson of a man, and his brother.  The DNA shared by the brother and the grandson HAS to be the DNA contributed to that grandson by his grandfather, from their common ancestor, the great grandfather.  So, in our situation above, Phoebe’s DNA is excluded.

The chart below shows the inheritance path for Lazarus matching.

Lazarus inheritance

Because Lazarus is comparing the DNA of Son Doe with Brother Doe – that eliminates any DNA from the brother’s wives, Sarah Spoon or Mary – because those lines are not shared between Brother Doe and Son Doe.  The only shared ancestors that can contribute DNA to both are Father Doe and Methusaleh Fisher.

The Lazarus instructions allow you to enter the direct descendants of the person/couple that you are reconstructing, then a second set of instructions asks for remaining relatives not directly descended, like siblings, parents, cousins, etc. In other words, those that should share DNA through the common ancestor of the person you are recreating.

To recreate Elijah, I entered all of the Vannoy cousins and then entered William (V) as a sibling since he is the proven son of Daniel Vannoy and Sarah Hickerson.

Here is what Lazarus produced.

lazarus elijah 1

Lazarus includes segments of 4cM and 500 SNPs.

The first thing I thought was, “Holy Moly, what happened to chromosome 15?”  I went back and looked, and sure enough, while almost all of the Elijah descendants do match on chromosome 15, William (V), kit 156020, does not match above the Lazarus threshold I selected.  So chromosome 15 is not included.  Finding additional people who are known to be from this Vannoy line and adding them to the “nondescendant” group would probably result in a more complete Elijah.

lazarus elijah 2

Next, to recreate Sarah Hickerson, I added all of the Vannoy cousins plus William (V) as descendants of Sarah Hickerson and then I added just the one Hickerson descendant, William, as a sibling.  William’s ancestor is proven to be the sibling of Sarah.

I didn’t know quite what to expect.

Clearly if the DNA from the Hickerson descendant didn’t match or triangulate with DNA from any of the Vannoy cousins at this higher level, then Sarah Hickerson wasn’t likely Elijah’s mother.  I wanted to see matching, but more, I wanted to see triangulation.

lazarus elijah 3

I was stunned.  Every kit except two had matches, some of significant size.

lazarus elijah 4

lazarus elijah 5 v2

Please note that locations on chromosomes 3, 4 and 13, above, are triangulated in addition to matching between two individuals, which constitutes proof of a common ancestor.  Please also note that if you were throwing away segments below 7cM, you would lose all of the triangulated matches and all but two matches altogether.

Clearly, comparing the Vannoy DNA with the Hickerson DNA produced a significant number of matches including three triangulated segments.

lazarus elijah 6

Where Are We?

I never have, and I never would recommend attempting to utilize random small match segments out of context.  By out of context, I mean simply looking at all of your 1cM segments and suggesting that they are all relevant to your genealogy.  Nope, never have.  Never would.

There is no question that many small segments are IBS by chance or identical by population.  Furthermore, working with small segments in endogamous populations may not be fruitful.

Those are the caveats.  Small segments in the right circumstances are useful.  And we’ve seen several examples of the right circumstances.

Over the past few weeks, we have identified guidelines and tools to work with small segments, and they are the same tools and guidelines we utilize to work with larger segments as well.  The difference is size.  When working with large segments, the fact that they are large serves an a filter for us and we don’t question their authenticity.  With all small segments, we must do the matching and analysis work to prove validity.  Probably not worthwhile if you have larger segments for the same group of people.

Working with the Vannoy data on chromosome 15 is not random, nor is the family from an endogamous population.  That segment was proven to be Vannoy prior to attempts to confirm or disprove the Hickerson connection.  And we’ve gone beyond just matching, we’ve proven the ancestral link by triangulation, including small segments.  We’ve now proven the Hickerson connection about 7 ways to Sunday.  Ok, maybe 7 is an exaggeration, but here is the evidence summed up for the Vannoy/Hickerson study from multiple vendors and tools:

  • Ancestry DNA Circle indicating that multiple Hickerson descendants match me and some that don’t match me, match each other. Not proof, but certainly suggestive of a common ancestor.
  • A total of 26 Hickerson or derivative family name matches to Vannoy cousins at Family Tree DNA. Not proof, but again, very suggestive.
  • 6 Charles Hickerson/Mary Lytle descendants match to Vannoy cousins at Family Tree DNA. Extremely suggestive, needs triangulation.
  • Triangulation of segments between Vannoy and Hickerson cousins at Family Tree DNA. Proof, but in this study we were only looking to determine whether small segment matches constituted proof.
  • Triangulation of multiple Hickerson/Vannoy cousins on chromosome 15 at GedMatch utilizing small segments and one to one matching. More proof.
  • Lazarus, at higher thresholds than the triangulation matching, when creating Sarah Hickerson, still matched 19 segments and triangulated three for a total of 73.2cM when comparing the Hickerson descendant against the Vannoy cousins. Further proof.

So, can small segment matching data be useful? Is there any reason NOT to accept this evidence as valid?

With proper usage, small segment data certainly looks to provide value by judiciously applying exactly the same rules that apply to all DNA matching.  The difference of course being that you don’t really have to think about utilizing those tools with large segment matches.  It’s pretty well a given that a 20cM match is valid, but you can never assume anything about those small segment matches without supporting evidence. So are larger segments easier to use?  Absolutely.

Does that automatically make small segments invalid?  Absolutely not.

In some cases, especially when attempting to break down brick walls more than 5 or 6 generations in the past, small segment data may be all we have available.  We must use it effectively.  How small is too small?  I don’t know.  It appears that size is really not a factor if you strictly adhere to the IBD/IBS guidelines, but at some point, I would think the segments would be so small that just about everyone would match everyone because we are all humans – so the ultimate identical by population scenario.

Segments that don’t match an individual and either or both parents, assuming you have both parents to test, can safely be disregarded unless they are large and then a look at the raw data is in order to see if there is a problem in that area.  These are IBS by chance.  IBS segments by chance also won’t triangulate further up the tree.  They can’t, because they don’t match your parents so they cannot come from an ancestor.  If they don’t come from an ancestor, they can’t possibly match two other people whose DNA comes from that ancestor on that segment.

If both parents aren’t available, or your small segments do match with your parents, I would suggest that you retain your small segments and map them.

You can’t recognize patterns if the data isn’t present and you won’t be able to find that proverbial needle in the haystack that we are all looking for.

Based on what we’ve seen in multiple case studies, I would conclude that small segment data is certainly valid and can play a valid role in a situation where there is a known or suspected relationship.

I would agree that attempting to utilize small segment data outside the context of a larger data match is not optimal, at least not today, although I wish the vendors would provide a way for us to selectively lower our thresholds.  A larger segment match can point the way to smaller segment matches between multiple people that can be triangulated.  In some situations, like the person A, B, C, D Hickerson-Vannoy situation I described earlier in this article, I would like to be able to drop the match threshold to reveal the small segment data when other matches are suggestive of a family relationship.

In the Hickerson situation, having the ability to drop the matching thresholds would have been the key to positively confirming this relationship within the vendor’s data base and not having to utilize third party tools like GedMatch – which require the cooperation of all parties involved to download their raw data files.  Not everyone transferred their data to Gedmatch in my Vannoy group, but enough did that we were able to do what we needed to do.  That isn’t always the case.  In fact, I have an nearly identical situation in another line but my two matches at Ancestry have declined to download their data to Gedmatch.

This not the first time that small segment data has played a successful role in finding genealogy solutions, or confirming what we thought we knew – although in all cases to date, larger segments matched as well – and those larger segment matches were key and what pointed me to the potential match that ultimately involved the usage of the small segments for triangulation.

Using larger data segments as pointers probably won’t be the case forever, especially if we can gain confidence that we can reliably utilize small segments, at least in certain situations.  Specifically, a small segment match may be nothing, but a small segment triangulated match in the context of a genealogical situation seems to abide by all of the genetic genealogy DNA rules.

In fact, a situation just arose in the past couple weeks that does not include larger segments matching at a vendor.

Let’s close this article by discussing this recent scenario.

The Adoptee

An adoptee approached me with matching data from GedMatch which included matches to me, Dean, Carl and Harold on chromosome 15, on segments that overlap, as follows.

adoptee chr 15

On the spreadsheet above, sent to me by the adoptee, we can see some matches but not all matches. I ran the balance of these 4 people at GedMatch and below is the matching chart for the segment of chromosome 15 where the adoptee matches the 4 Vannoy cousins plus William(H), the Hickerson cousin.

  Me Carl Dean Harold Adoptee
Me NA FTDNA FTDNA GedMatch GedMatch
Harold GedMatch FTDNA FTDNA NA GedMatch
Adoptee GedMatch GedMatch GedMatch GedMatch NA
William (H) GedMatch GedMatch GedMatch GedMatch GedMatch

I decided to take the easy route and just utilize Lazarus again, so I added all of the known Vannoy and Hickerson cousins I utilized in earlier Lazarus calculations at Gedmatch as siblings to our adoptee.  This means that each kit will be compared to the adoptees DNA and matching segments will be reported.  At a threshold of 300 SNPs and 4cM, our adoptee matches at 140cM of common DNA between the various cousins.

adoptee vannoy match

Please note that in addition to matching several of the cousins, our adoptee also triangulates on chromosomes 1, 11, 15, 18, 19 and 21.  The triangulation on chromosome 21 is to two proven Hickerson descendants, so he matches on this line as well.

I reduced the threshold to 4cM and 200 SNPs to see what kind of difference that would make.

adoptee vannoy match low threshold

Our adoptee picked up another triangulation on chromosome 1 and added additional cousins in the chromosome 15 “sticky Vannoy” cluster and the chromosome 18 cluster.

Given what we just showed about chromosome 15, and the discussions about IBD and IBS guidelines and small matching segments, what conclusions would you draw and what would you do?

  1. Tell the adoptee this is invalid because there are no qualifying large match segments that match at the vendors.
  2. Tell the adoptee to throw all of those small segments away, or at least all of the ones below 7cM because they are only small matching segments and utilizing small matching segments is only a folly and the adoptee is only seeing what he wants to see – even though the Vannoy cousins with whom he triangulates are proven, triangulated cousins.
  3. Check to see if the adoptee also matches the other cousins involved, although he does clearly already exceeds the triangulation criteria to declare a common ancestor of 3 proven cousins on a matching segment. This is actually what I did utilizing Lazarus and you just saw the outcome.

If this is a valid match, based on who he does and doesn’t match in terms of the rest of the family, you could very well narrow his line substantially – perhaps by utilizing the various Vannoy wives’ DNA, to an ancestral couple.  Given that our adoptee matches both the Vannoys and the Hickersons, I suspect he is somehow descended from Daniel Vannoy and Sarah Hickerson.

In Conclusion

What is the acceptable level to utilize small segments in a known or suspected match situation?

Rather than look for a magic threshold number, we are much better served to look at reliable methods to determine the difference between DNA passed from our ancestors to us, IBD, and matches by chance.  This helps us to establish the reliability of DNA segments in individual situations we are likely to encounter in our genealogy.  In other words, rather that throw the entire pile of wheat away because there is some percentage of chaff in the wheat, let’s figure out how to sort the wheat from the chaff.

Fortunately, both parental phasing and triangulation eliminate the identical by chance segments.

Clearly, the smaller the segments, even in a known match situation, the more likely they are identical by population, given that they triangulate.  In fact, this is exactly how the Neanderthal and Denisovan genomes have been reconstructed.

Furthermore, given that the Anzick DNA sample is over 12,000 years old, Identical by population must be how Anzick is matching to contemporary humans, because at least some of these people do clearly share a common ancestor with Anzick at some point, long ago – more than 12,000 years ago.  In my case, at least some of the Anzick segments triangulate with my mother’s DNA, so they are not IBS by chance.  That only leaves identical by population or identical by descent, meaning within a genealogical timeframe, and we know that isn’t possible.

There are yet other situations where small segment matches are not IBS by chance nor identical by population.  For example, I have a very hard time believing that the adoptee situation is nothing but chance.  It’s not a folly.  It’s identical by descent as proven by triangulation with 10 different cousins – all on segments below the vendor matching thresholds.

In fact, it’s impossible to match the Vannoy cousins, who are already triangulated individually, by chance.  While the adoptee match is not over the vendor threshold, the segments are not terribly small and they do all triangulate with multiple individuals who also triangulate with larger segments, at the vendors and on different chromosomes.

This adoptee triangulated match, even without the Hickerson-Vannoy study disproves the blanket statement that small segments below 5cM cannot be used for genealogy.  All of these segments are 7.1cM or below and most are below 5.

This small segment match between my mother and her first cousins also disproves that segments under 5cM can never be used for genealogy.

Two cousins combined

This small segment passed from my mother to me disproves that statement too – clearly matching with our cousin, Cheryl.  If I did not receive this from my mother, and she from her parent, then how do we match a common cousin???

me mother small seg

More small segment proof, below, between my mother and her second cousin when Lazarus was reconstructing my mother’s father.

2nd cousin lazarus match

And this Vannoy Hickerson 4 cousin triangulated segment also disproves that 5cM and below cannot be used for genealogy.

vannoy hickerson triang

Where did these small segments come from if not a common ancestor, either one or several generations ago?  If you look at the small segment I inherited from my mother and say, “well, of course that’s valid, you got it from your mother” then the same logic has to apply that she inherited it from her parent.  The same logic then applies that the same small segment, when shared by my mother’s cousin, also came from the their common grandparents.  One cannot be true without the others being true.  It’s the same DNA. I got it from my mother.  And it’s only a 1.46cM segment, shown in the examples above.

Here are my observations and conclusions:

  • As proven with hundreds of examples in this and other articles cited, small segments can be and are inherited from our ancestors and can be utilized for genetic genealogy.
  • There is no line in the sand at 7cM or 5cM at which a segment is viable and useful at 5.1cM and not at 4.9cM.
  • All small segment matches need to be evaluated utilizing the guidelines set forth for IBD versus IBS by chance versus identical by population set forth in the articles titled How Phasing Works and Determining IBD Versus IBS Matches and Demystifying Autosomal DNA Matching.
  • When given a choice, large segment matches are always easier to use because they are seldom IBS by chance and most often IBD.
  • Small segment matches are more likely to be IBS by chance than larger matches, which is why we need to judiciously apply the IBD/IBS Guidelines when attempting to utilize small segment matches.
  • All DNA matches, not just small segments, must be triangulated to prove a common ancestor, unless they are known close relatives, like siblings, first cousins, etc.
  • When working in genetic genealogy, always glean the information from larger matches and assemble that information.  However, when the time comes that you need those small segments because you are working 5, 6 or 7 generations back in time, remember that tools and guidelines exist to use small segments reliably.
  • Do not attempt to use small segments out of context.  This means that if you were to look only at your 1cM matches to unknown people, and you have the ability to triangulate against your parents, most would prove to be IBS by chance.  This is the basis of the argument for why some people delete their small segments.  However, by utilizing parental phasing, phasing against known family members (like uncles, aunts and first cousins) and triangulation, you can identify and salvage the useable small segments – and these segments may be the only remnants of your ancestors more than 5 or 6 generations back that you’ll ever have to work with.  You do not have to throw all of them away simply because some or many small segments, out of context, are IBS by chance.  It doesn’t hurt anything to leave them just sit in your spreadsheet untouched until the day that you need them.

Ultimately, the decision is yours whether you will use small segments or not – and either decision is fine.  However, don’t make the decision based on the belief that small segments under some magic number, like 5cM or 7cM are universally useless.  They aren’t.

Whether small segments are too much work and effort in your individual situation depends on your personal goals for genetic genealogy and on factors like whether or not you descend from an endogamous population.  People’s individual goals and circumstances vary widely.  Some people test at Ancestry and are happy with inferential matching circles and nothing more.  Some people want to wring every tidbit possible out of genealogy, genetic or otherwise.

I hope everyone will begin to look at how they can use small segment data reliably instead of simply discarding all the small segments on the premise that all small segment data is useless because some small segments are not useful.  All unstudied and discarded data is indeed useless, so discarding becomes a self-fulfilling prophecy.

But by far, the worst outcome of throwing perfectly good data away is that you’ll never know what genetic secrets it held for you about your ancestors.  Maybe the DNA of your own Sarah Hickerson is lurking there, just waiting for the right circumstances to be found.



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Ancestor Reconstruction

No, this is not Jurassic Park and we’re not actually recreating or cloning our ancestors – just on paper.

Back in early 2012, I began to discuss the possibility of using chromosome mapping of descendants to virtually recreate ancestors.

In 2013, I wrote a white paper about how to do this, and circulated it among a group of scientists who I was hoping would take the ball and run, creating tools for genetic genealogists.  So far, that hasn’t happened, but what has happened is that I’ve adapted a tool created by Kitty Cooper for something entirely different than its original purpose to do a “proof of concept.”

Kitty Cooper created the Ancestor Chromosome Mapper to allow people to map the DNA contributed by different ancestors on their chromosomes.  It’s exciting to see your ancestors mapped out, in color, on your chromosomes.

I utilized Kitty’s tool, found here, to map the proven DNA of my ancestors, below, utilizing autosomal matching and triangulation, to create this ancestor map of my own chromosomes.  As you can see there are still a lot of blank spaces.

Roberta's ancestor map2

After thinking about this a bit, I realized that I could do the same thing for my ancestors.

The chromosomes shown would be those of an individual ancestor, and the DNA mapped onto the chromosomes would be from the proven descendants that they inherited from that ancestor.  Eventually, with enough descendants we could create a “virtual file” for that ancestor to represent themselves in autosomal matching.  So, one day, I might create, or find created by someone else, a DNA “recreated” file for Abraham Estes, born in 1647 in Nonington, Kent, or for Henry Bolton, born about 1760 in England, or any of my other ancestors – all from the DNA of their descendants.

I decided a while back to take this concept for a test spin.

I wanted to see a visual of Joseph Preston Bolton’s DNA on his chromosomes, and who carries it today.  I wrote about this in Joseph’s 52 Ancestors article.

Utilizing Kitty Cooper’s wonderful ancestor chromosome mapping tool, a little differently than she had in mind, I mapped Joseph’s DNA and the contributors are listed to the right of his chromosome.  You can build a virtual ancestor from their descendants based on common matching segments, so long as they don’t share other ancestral lines as well.  I have only utilized the proven, or triangulated DNA segments, where three people match on the same segment.

joseph bolton reconstructed

We have a couple more DNA testers that descended from Joseph Bolton’s father, Henry Bolton through children other than Joseph Preston Bolton.  Adding these segments to the chromosome chart generated for Joseph Preston Bolton, we see the confirmed Henry Bolton segments below.

henry bolton proven

On the chart above, I’ve only used proven segments.

On the next chart I have not been able to “prove” all of the segments through triangulation (3 people), but if all of the provisional segments are indeed Bolton segments, then Henry’s chromosome map would have a few more colored segments.  Clearly, we need a lot more people to test to create more color on Henry’s map, but still, it’s pretty amazing that we can recreate this much of Henry’s chromosome map from these few descendants.

henry bolton probably

There’s a lot of promise in this technique.  Henry Bolton was married twice.  By looking at the DNA the two groups of children, 21 in total, have in common, we know that their common DNA comes from Henry himself.  DNA that is shared between only the groups descended from first wife, Catherine Chapman, but not from second wife, Nancy Mann, or vice versa, would be attributed to the wife of the couple.  Since Henry was married twice, with enough testers, it would be possible to reconstruct, in part, at least some of the genome of both wives, in addition to Henry.

Now, think for a minute, a bit further out in time.

We don’t know who Nancy Mann’s parents are for sure, although we’ve done a lot of eliminating and we know, probably, who her father was, and likely who her grandfather and great-grandfather were….but certainty is not within grasp right now.

But, it will be in the future through ancestor reconstruction.

Let’s say that the descendants of John Mann, the immigrant, reconstruct his genome.  He had 4 known sons and they had several children, so that would be possible.  John, the immigrant, is believed to be Nancy’s great-grandfather through son John Jr.

Now, let’s say that some of those segments that we can attribute through Henry Bolton’s children, as described above, are attributable to Nancy Mann.  The X chromosome match above is positively Nancy’s DNA.  How do I know that?  because it came through her son, Joseph Preston Bolton, and men don’t inherit an X chromosome from their father, only their mother.  So today, 3 descendants carry that segment of Nancy Mann’s X chromosome.

Let’s say that one of the Nancy Mann’s proven DNA segments (not the X, because John didn’t give his X to his son John) matches smack dab in the middle of one of the proven “John Mann” segments.  We’ve just proven that indeed, Nancy is related to John.

Think about the power of this for adoptees, for those who don’t know who their parent or parents are for other reasons, and for those of us who have dead end brick walls who are wives with no surnames.  Who doesn’t have those?

We have the potential, within the foreseeable future, to create “ancestor libraries” that we can match to in order to identify our ancestors.  Once the ancestor is reconstructed, kind of like reconstituting something dehydrated with water, we’ll be able to utilize their autosomal DNA file to make very interesting discoveries about them and their lives.  For example, eye color – at GedMatch today there is an eye color predictor.  There are several ethnicity admixture tools.  Want to know if your ancestor was ethnically admixed?  Virtually recreate them and find out.

Once recreated, we will be able to discover hair color, skin color and all of the other traits and medical conditions that we can today discover through the trait testing at Family Tree DNA and the genetic predispositions that Promethease reveals.

Yes, there will be challenges, like who creates those libraries, moderates any disputes and where are they archived for comparison….but those are details that can be worked out.  Maybe that’s one of the new roles of project administrators or maybe we’ll have ancestor administrators.

Someday, it may be possible to construct an entire family tree from your DNA combined with proven genealogy trees – not by intensely laborious work like it’s done today, but with the click of a button.

And that someday is very likely within our lifetimes, and hopefully, shortly.  The technology and techniques are here to do it today.

I surely hope one of the vendors implements this functionality, and soon, because, like all genealogists, I have a list of genealogy mysteries that need to be solved!!!



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Big Y Release

Drum roll…the big day is finally here.

Family Tree DNA held a webinar meeting today to explain the new Big Y product features for a number of us who blog or otherwise educate within the genetic genealogy community.

First, the results will begin rolling today, not tomorrow.  100 will initially be released today and the balance of the initial orders will be released as they finish QA over the next month, at which point, Family Tree DNA anticipates their backlog will be resolved.  There were thousands of tests ordered.  They aren’t saying how many thousands.

First, a little background.  There are 36,562 known Y SNPs in the Family Tree DNA data base that everyone is being compared to.  In the example we saw of the delivered product, 25,749 has been found and callable at a high confidence rate in the individual being tested and were reported.  Low confidence calls are not reported on this personal delivery page, but are included in the data download files.

Big Y landing

On the customer’s personal page, there are two tabs.  The first Tab is for reporting against known SNPs.

Y page 1 cropped

The second is for Novel Variations, in other words, SNPs not on the list of 36,562 known and previously named SNPs.

Y page 2

In essence, Family Tree DNA has implemented a 4 step process.

  1. An individual’s sequenced data is compared to the SNP data base and divided into two categories, known and previously unknown.  The customer’s data is delivered based on these two categories.
  2. All customer data is being loaded into a mammoth size data base at which point it will be determined which SNPs (please see the definition of a SNP here) are actually undiscovered SNPs that will be named, and which are truly novel, family or clan variants.
  3. New SNPs that are found in enough of the population will be named and will be added to the haplotree.
  4. Novel variants will remain that, and will continue to be reported on client pages.

Family Tree DNA is still working on items 2-4.  In addition, they are working on a white paper which will be out in the next 6 weeks or so that will discuss things like the average number of novel SNPs per person being discovered, mutation rates, performance metrics and cross validation of platforms between the next gen sequencing Illumina equipment, Sanger sequencing and chip based sequencing, like the Geno 2.0 chip.

What’s Being Reported?

According to Dr. David Mittelman, the Y chromosome has about 60 million letters.  About half of those are inverted repeats and are therefore not sequenceable.

Of the balance, there are several with poor readability, for example, some that simulate the X, etc.  These are also not useful or reliable to read.

That leaves about 10 million, these being the gold standard of Y sequencing.  Family Tree DNA tries to read about 13.5 million of these base pairs.  They promised 10 million positions when they announced this product.  They are delivering between 11.5 and 12.5 million positions per person.  They also promised about 25,000 common variants, meaning known SNPs and they are delivering between 25,000 and 30,000 per person.  This is only counting medium to high confidence calls.  The low confidence calls are included in the download files, but not counted in this total or shown on your personal page.

Exactly how many locations are reported for any individual are shown on the bottom left hand side of the page.  This example is generic.  Yours might say something like, “Showing 1 of 10 of 25,000 of 36,564.”  In this case, 25,000 would be the number of SNPs read and called on your test.

Big Y total

All 25,000 or so results are being shown, both positive and negative.  That way, there is no question about whether a specific location was tested, or the outcome.  Of course, the third and fourth outcome options are a no-call or poor confidence call at that location.

All novel mutations are being reported by reference number so that they can be compared to like data from any source, as opposed to an “in-house” assigned number.

Insertions and deletions are also in the download files, but not reported on the customer’s delivery page.

Personal data is also searchable by SNP.

SNP search

Individual SNP Testing

After steps 2 and 3 have occurred, it has to be determined which SNPs are found in a high enough percentage of a population to warrant primer development to test individual SNP positions.

Family Tree DNA also clarified something from the November conference.  The 2000 SNP limit is only how many SNPs can be loaded at one time, not the total number they will ever develop primers for or test for.  They will do what makes sense in terms of the SNP being present in enough of the market to warrant primer development.  With the very large number of Novel SNPs being discovered, it wouldn’t make much sense to purchase 50 individual SNP tests at $39 each.  The break even point today, at $39, would be 17 individual SNPs, as compared to the $695 Big Y test.  I expect that eventually the demand for individual SNP testing will decrease substantially.

Downloadable Files

Available on everyone’s page is the ability to download 2 files, a VCF (variant call file) which lists the variants identified as compared to the human reference sequence and the BED file which is a text file which shows a range of positions that passed the QC.

They will also be making available the BAM raw data files within the next week or so, but are finalizing the delivery methodology due to the very large file sizes involved.

The Much Anticipated HaploTree

If I had a dollar for every time someone has asked when the new tree would be available, I’d be a rich woman.  As we all know, there have been a couple of problems with the tree.  The new tree is 7 to 8 times the size of the 2010 tree.  The tree, of course, has been cast in warm jello, an ever-moving target.  And with the SNP tsumani that has been arriving with the full sequencing of the Y chromosome, that tree will very shortly be much larger still.

Bennett Greenspan said today that an updated tree is, “Needed, desired and will be delivered.”  He went on to say that they have had two teams working together with Nat Geo for the past couple of months to both finalize the tree itself and to work on the customer interface.  Since the tree is much larger, it’s not as easy as the older trees which could be seen at a glance and easily navigated.  Furthermore, there is also the matter of integration with National Geographic.

Bennett says an updated tree will be delivered “within the next several weeks.”

New SNPs that are discerned to be SNPs and not novel/clan or family variations will then be named and added to the tree.


The initial release of Big Y data will be just that, a release of the results of the data, displayable on your personal page and downloadable.  The newly found SNPs will not initially update the current haplotree on your personal page.  This is the same issue we have today with the transfer and integration of Nat Geo data, because the tree is not current, so this is nothing new.  The implementation of the new tree however, will remedy both problems.

The Future

Never happy with what we have, genetic genealogists will want a way to match to other people on SNPs, just like we do today with STR markers.  In fact, we’ll want a way to integrate that matching and discern what it means to our own private family or clan situations.

Family Tree DNA is aware of that, planning for it, and welcomes feedback for how they can make this information even more useful in the future than it is today.

New Orders

I expect this delivery of new information via Big Y results will indeed spur a new interest in ordering this test from people who were waiting to see exactly what was being delivered.  For those people ordering now, they can expect an 8-10 week turnaround, so long as additional vials aren’t required for testing.

For More Information

Elise Friedman is holding the free Big Y Webinar tomorrow, Friday, February 28th.  You can read about it, sign up and learn how to access this and other webinars after their initial showing at this link.

Family Tree DNA FAQ pages you’ll want to visit are here and here.



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