Category Archives: IBD – Identical by Descent

Pedigree Collapse and DNA – Plus an Easy-Peasy Shortcut

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Pedigree collapse can be responsible for you sharing more DNA than expected with another person.

What is pedigree collapse?

Pedigree collapse occurs when you descend from the same ancestor(s) through more than one path. In other words, you descend from those ancestors through two different children. Therefore, when matching with someone else who descends through those ancestors, you may share more DNA than would be expected from that level of relationship on the surface, meaning without pedigree collapse.

Endogamy is different and means that you descend from a community of ancestors who descend from the same group of ancestors. Often out-marriage is discouraged or otherwise impossible, so all of the group of people share common ancestors, which means they often match on segments without sharing close ancestors. Examples of descent from endogamous populations are Jewish, Amish, Brethren, Acadian, Native Hawaiian, Māori, and Native American people, among others.

I wrote about the difference between pedigree collapse and endogamy in the article, What’s the Difference Between Pedigree Collapse and Endogamy?

I’ve also written about endogamy in the following articles:

Degrees of Consanguinity

If you’re a genealogist, and especially if you’ve worked with Catholic church records, you’ve probably heard of “degrees of sanguinity,” which are prohibited blood relationships in marriage. For example, siblings are prohibited from marrying because they are too closely related, according to church doctrine.

By SVG remake by WClarke based on original by User:Sg647112c – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=54804980

Today, we think of the genetic results of inbreeding, but originally, relationships (and consanguinity) also had to do with inheritance.

Essentially, marriages are prohibited by degree of sanguinity, and that degree is calculated based on this relationship chart. Prohibited degrees of consanguinity changed over time. Sometimes, a priest granted dispensation for a couple to wed who was of a prohibited degree of sanguinity. That’s a genealogy goldmine because it tells you where to look for common ancestors. It also tells you something else – that you may share more DNA with other descendants of that couple than one would otherwise expect.

More Than You Ever Expected

Recently, I’ve been working with an academic research team on a very interesting ancient DNA case that involves pedigree collapse. Doing the genealogy and genetic work on how much DNA was expected in a match without pedigree collapse, and how much was expected with pedigree collapse, was very interesting.

The team was working to confirm relationships between people in a cemetery. The burials shared more DNA than anticipated for who the people were believed to be. Enter pedigree collapse.

I can’t disclose the circumstances just yet – but I will as soon as possible. It’s an extremely interesting story.

We needed to ensure that readers, both academic and more generally understood pedigree collapse and our calculations. Why did burials share higher than expected DNA than indicated by the expected relationships? This puzzle becomes much more interesting when you add in pedigree collapse.

Academic researchers and scientists have access to models and mathematical algorithms that normal air-breathing humans don’t have easy access to.
So, what do you do if you and a match have a known pedigree collapse in your tree? How much DNA can you expect to share, and how do you calculate that?

These are all great questions, so let’s take a look.

I’m sharing the PowerPoint slides I prepared for our team on this topic. I’ve removed anything that would identify or even hint at the project and modified the slides slightly for easier consumption.

This presentation has never been given publicly, so you’re first! It seemed a waste to do this work and not share it!

Pedigree Collapse and DNA

Pedigree collapse occurs when you share an ancestor or ancestors through different pathways. In this case, the person at the bottom is the child of parents who were third cousins, but the father’s grandparents were also first cousins.

First cousin marriages were common in the not-too-distant past. Today, you could easily marry your third or fourth cousin and not even realize it unless someone in your family just happened to be a genealogist.

Genealogists use various tools to calculate the expected amount of shared DNA in relationships – first cousins, siblings, or half-siblings, for example. Both the Shared cM Project at DNAPainter and SegcM at DNA-Sci Tools provide tools.

Take a look at the article, DNA: In Search of…Full and Half-Siblings, for some great examples.

First cousins share common grandparents. Their child inherits DNA from two paths that lead back to the same ancestors. Some of that DNA will be the same, meaning the child will or can inherit the same ancestral segment from both parents, and some will be different segments from those ancestors that the parents do not share with each other.

Inheritance – How It Works

Let’s look at inheritance to see how this happens.

Let’s start with full and half-siblings.

Each child inherits half of their DNA from each parent, but not entirely the same half (unless they are identical twins.)

Therefore, full siblings will match on about 50% of their DNA, which is illustrated by the segments on the chromosome browser. However, and this will be important in a minute, about 25% of their DNA is exactly the same, when compared to each other, on the chromosome inherited from their father and mother at the same location.

On the chromosome browser, you can see that three siblings do match. One sibling (the grey background chromosomes) is the person both other full siblings are being compared to, in the example above.

What you can’t determine is whether they share the exact same DNA on both their mother and father’s Chromosome 1, where the matches overlap, for example. We know they both match their sibling, but the top person could match the sibling due to a match from their paternal chromosome in that location, and the bottom person could match due to their maternal chromosome. There’s no way to know, at least not from that view.

The areas where the siblings share exactly the same DNA on both their maternal and paternal chromosome, both, with each other are called Fully Identical REgions (FIR), as compared to Half Identical Regions (HIR) where the siblings match on either their maternal or paternal copy of the chromosome, but not both.

23andMe used to provide a tool that displayed both types of matches.

Since the data exposure incident at 23andMe, they no longer provide this lovely tool, and since that help page is now gone as well, I doubt this view will ever be returned. Fortunately, I grabbed a screenshot previously.

The dark purple segments are fully identical, meaning that these two full siblings match on both their maternal and paternal chromosomes in that location. The magenta are half identical, which means they match on EITHER the maternal or paternal chromosome in that location but not on both chromosomes. Of course, no color (light grey) means there is no match at that location.

Please note that because 23andMe counts fully identical regions (FIR) twice, their total matching cMs are elevated. The other companies do NOT count those regions twice.
GEDmatch also shows both full and half-identical regions as described more fully, here.

In this full-sibling example from GEDmatch, the green segments are fully identical regions across both the maternal and paternal chromosomes.

The definition of FIR is that two people match on both their mother’s and father’s DNA on the same chromosome. Therefore, in following generations, there technically should not be FIR matches, but in some instances we do find FIR matches outside of full siblings.

Moving down another generation, first cousins may share SOME fully identical DNA, especially if they are from an endogamous population or their mothers are related, but less, and it’s generally scattered.

Here’s my Mom’s GEDmatch comparison to her first cousin. The purple-legend segment shows a match, and the green within that match shows fully identical locations.

You can easily see that these are very scattered, probably representing “chance” or population-based fully identical matching locations within a segment. Comparatively, the green FIR segments for full siblings are dense and compact, indicating a segment that is fully identical.

Evaluating matches for dense FIR segments (known as runs of homozygosity – ROH) is a good indicator of parental relatedness.

Double Cousins

Of course, if these people were double first cousins, where the wives of the siblings were sisters to each other – the first cousins would have large patches of dense green FIR segments.

First cousins share grandparents.

Double first cousins occur when two people share both sets of grandparents, meaning that brothers marry sisters. Normal first cousins share about 12.5% of their DNA, but double first cousins share about 25% of their DNA.

In this case, Sharon and Donna descend from two brothers, James and Henry, who were sons of Joseph and Jane. In this scenario, James and Henry married unrelated women, so Sharon and Donna are first cousins to each other.

Double first cousins share both sets of grandparents so they would inherit FIR from both sets of siblings.

You need to be aware of this, but for now, let’s stick with non-double relationships. You’re welcome!

DNA Inheritance

Here’s a different example of DNA inheritance between two siblings.

  1. You can see that in the first 50 cM segment, both siblings inherited the same DNA from both parents, so they match on both their mother’s and father’s chromosomes. They match on both the 50 cM green and 50 cM pink segments. 23andMe would count that as 100 cMs, but other vendors only count a segment IF it matches, NOT if it matches twice. So, other vendors count this as a 50 cM match.
  2. In column two, these two people don’t match at all because they inherited different DNA from each parent. In this example, Person 1 inherited their maternal grandmother’s segment, and Person 2 inherited their maternal grandfather’s segment.
  3. In column three, our siblings match on their paternal grandmother’s segment.
  4. In column four, no match again.

How much can we expect to inherit at different levels – on average?

Different tools differ slightly, and all tools provide ranges. In our example, I’ve labeled the generations and how much shared DNA we would expect – WITHOUT pedigree collapse.

Ancestral couple Inherited cM Inherited %
Gen 1 – Their children 3500 cM 50
Gen 2 – Grandchildren 1750 cM 25
Gen 3 – Great-Grandchildren 875 cM 12.5
Gen 4 – GG-Grandchildren 437.5 6.25
Gen 5 – GGG-Grandchildren 218.75 3.125
Gen 6 – GGGG-Grandchildren 109.375 1.5625
Gen 7 – GGGG-Grandchildren 54.6875 .078125

Please note that this is inherited DNA, not shared (matching) DNA with another person.

Adding in pedigree collapse, you can see that we have three Gen 1 people involved, three Gen 2 descendants, and two Gen 3 and Gen 4 people.

Each of those people inherit and pass on segments from our original couple at the top.
We have three distinct inheritance paths leading from our original couple to Gen 5.
We have a first cousin marriage at Gen 2, at left, which means that their child, Gen 3, will have an elevated amount of the DNA of their common ancestors.

In Gen 4, two people marry who both descend from a common couple, meaning their child, Gen 5, descends from that couple in three different ways.

Did your eyes just glaze over? Well, mine did, too, which is why I had to draw all of this out on paper before putting it into PowerPoint.

The Gen 5 child inherits DNA from the ancestral couple via three pathways.
The next thing to keep in mind is that just because you inherit the DNA from an ancestor does not mean you match another descendant. Inheritance is not matching.

You must inherit before you can match, but just because you and someone else have inherited a DNA segment from a common ancestor does not guarantee a match. Those segments could be in different locations.

Categories of DNA

When dealing with inheritance and descent, we discuss four categories of DNA.

  • In the first generation, full siblings will, in about 25% of their locations, share the same DNA that has been inherited from both parents on the same chromosome. In other words, they match each other both maternally and paternally at that location. Those are FIR.
  • The DNA you inherit from an ancestor.
  • The DNA that both you and your cousin(s) inherit from a common ancestor and match on the same location. This is shared DNA.
  • The DNA that both you and your cousin(s) inherit from a common ancestor, but it’s not in the same location, so you do not match each other on that segment. Just because you inherit DNA from that ancestor does not necessarily mean that your cousin has the same DNA from that ancestor. This is inherited but not shared.

Inheritance is Not The Same as Matching

Inheritance is not the same thing as matching.

Inheriting our ancestor’s DNA isn’t enough. We need to match someone else who inherited that same segment in order to attribute the segment to that specific ancestor.

Depending on how close or distant the relationship, two people may share a lot of DNA (like full siblings), or one segment in more distant matches, or sometimes none at all. As we reach further back in time, we inherit less and less of our increasingly distant ancestors’ DNA, which means we match increasingly fewer of their descendants. I wrote about determining ancestral percentages in the article,  Ancestral Percentages – How Much of Them is in You?

Based on how much DNA we share with other known relatives, we can estimate relationships.

Pedigree collapse, where one descends from common ancestors more than once, increases the expected amount of inherited DNA, which in turn increases the probability of a shared match with other descendants.

Ancestral Couple Matching Between Shared DNA ~cM Shared DNA ~% Range (Shared cM Project) FIR – Identical DNA
Generation 1 Full Siblings 2600 50 1613-3488 25%
Generation 2 First Cousins 866 12.5 396-1397 0
Generation 3 Second Cousins 229 3.125 41-592 0
Generation 4 Third Cousins 73 0.78125 0-234 0

Here’s an example through third cousins, including expected FIR, fully identical regions where full siblings match each other on both their maternal and paternal chromosomes in the same location.

I provided a larger summary chart incorporating the information from public sources, here, minus FIR.

Of course, double cousins, where two pairs of siblings marry each other, represent another separate level of complexity. DNA-Sci’s Double Cousin Orogen explains this here and also provides a tool.

Double cousins, meaning when two pairs of siblings marry each other, are different from doubly related.

Doubly related means that two people descend from common ancestors through multiple paths, meaning multiple lines of descent. Doubly related is pedigree collapse. Double cousins is pedigree collapse on steroids.

Pedigree Collapse, aka Doubly Related

Calculating expected inherited DNA from multiple lines of descent is a bit more challenging.

A handy-dandy chart isn’t going to help with multiple relationships because the amount of expected shared DNA is based on the number of and distance of relationships.

Please note that this discussion excludes X-DNA matching which has its own inheritance path.

It’s time for math – but I promise I’ll make this relatively easy – pardon the pun.

What’s Behind the Math?

So, here’s the deal. I want you to understand why and how this works. You may not need this information today, but eventually, you probably will. This is one of those “refer back to it” articles for your personal library. Read this once as a conceptual overview, then read it again if you need to work through the relationships.

This is easy if you take it one step at a time.

First, we calculate each path separately.

In the first generation, full siblings inherit identical (FIR) DNA on both their mother’s and father’s chromosomes.

In the second generation, the male inherits the maternal segment, and the female inherits the paternal segment.

In the third generation, their child inherits those segments intact from both of their parents. The child inherits from the ancestral couple twice – once through each parent.

In generation 1, those two segments were FIR, fully identical regions. Both of those men married unrelated wives. When their children, Gen 2, were born, they had either the maternal or paternal segment from their father because they had an entirely different segment in that location from their mother.

However, the child in Gen 3 inherited the original green segment from their father and the original pink segment from their mother – reuniting those FIR segments in later generations.

First Cousin’s Child

Let’s calculate the inheritance for the child of those two first cousins who married.

Ancestral couple Inherited cM Inherited %
Gen 3 – Great-Grandchildren 875 cM 12.5
Gen 3 – Great-Grandchildren 875 cM 12.5
Total 1750 cM 25

Normally, a Gen 3 person inherits roughly 875 cM, or 12.5% of their great-grandparent’s DNA. However, since their grandparents were first cousins, they inherit about twice that amount, or 1750 cM.

While a Gen 3 person inherits as much as a grandchild (25%) normally would from the original couple, they won’t match on all of that DNA. When matching, we need to subtract some of that DNA out of the equation for two reasons:

  • In the first generation, between siblings, some of their DNA was fully identical and cannot be identified as such.
  • In the second generation, they will each have some parts of the ancestral couple’s DNA that will not match the other person. So, they inherit the same amounts from their common ancestors, but they can only be expected to match on about 25% of that amount two generations later.

However, the child of first cousins who marry inherits more DNA of the common ancestors than they would if their parents weren’t related. It’s just that some of that DNA is the same, potentially on the maternal and paternal chromosomes again, and some won’t match at all.

While matching DNA is the whole point of autosomal DNA testing, fully identical DNA matching regions (FIR) cannot be identified that way. For the most part, other than identifying full and half-siblings, sometimes pedigree collapse, and parent-relatedness, fully identical DNA isn’t terribly useful for genealogy. However, we still need to understand how this works.

It’s OK if you just want to say, “I know we’ll share more DNA due to pedigree collapse,” but if you want to know how much more to expect, keep reading. I’d really like for you to understand use cases and be able to track those segments.

Remember, we will learn a super-easy shortcut at the end, so for now, just read. It’s important to understand why the shortcut works.

Sibling Inheritance Versus Matching

In order to compare apples to apples, sometimes we need to remove some portion of DNA in our calculations.

Remember story problems where you had to “show your work”?

Calculating Expected DNA

Here’s the step-by-step logic.

Ancestral couple Inherited Non-Identical cM Inherited %
Gen 1 first son 3500 50
Gen 1 second son 3500 50
Less identical segments (FIR) -1750 (subtracted from one child for illustration) 25
Gen 2 son 1750 25
Gen 2 daughter married Gen 2 son 875 12.5
Gen 3 – Their child path through Gen 2 son 875 cM 12.5
Gen 3 – Their child path through Gen 2 mother 437.5 cM 6.25
Their child total without removing identical segments 1750 cM 25
Their child total after removing identical segments 1312.5 18.75

Category cMs Most Probable Degree Relationship
No Pedigree Collapse 875 98% Great grandparent or great-grandchild, great or half aunt/uncle, great or half niece/nephew, 1C 3
Pedigree Collapse without identical segment removal 1750 100% Grandparent, grandchild, aunt/uncle, half-sibling, niece/nephew 2
Pedigree Collapse after identical segment removal 1312.5 56% grandparent, grandchild, aunt/uncle, niece/nephew, half-sibling 2

Just because you HAVE this much shared (and/or identical) DNA doesn’t mean you’ll match on that DNA.

Next, let’s look at Gen 5 child who inherited three ways from the ancestors.

If you think, “This will never happen,” remember that it did, which is why I was working through this story problem. It’s not uncommon for families to live in the same area for generations. You married who you saw – generally, your family and neighbors, who were likely also family.

Let’s take a look at that 5th generation child.

The more distantly related, the less pedigree collapse affects matching DNA. That’s not to say we can ignore it.

Here’s our work product. See, this isn’t difficult when you take it step by step, one at a time.

Ancestral couple Inherited Non-Identical cM Inherited %
Gen 3 Child total after removing identical segments 1312.5 18.75
Gen 4 father – half of Gen 3 father 656.25 9.375
Gen 5 child – half of Gen 4 father 328.125 4.6875
Gen 5 child – mother’s side calculated from ancestral couple normally 218.75 3.125
Total for Gen 5 Child 546.875 7.8125

Inheritance Ranges

Lots of factors can affect how much DNA a person in any given generation inherits from an ancestor. The same is true with multiple paths from that same ancestor. How do we calculate multiple path inheritance ranges?

As with any relationship, we find a range, or combined set of ranges for Gen 5 Child based on the multiple pathways back to the common ancestors.

Gen 5 Child Inherited Non-Identical cM Inherited %
Without removing either paternal or maternal identical cMs 656.25 9.375
After removing paternal identical cMs only 546.875 7.8125

 
After removing maternal cMs only 546.875 7.8125

 
After removing both paternal and maternal identical cMs 362.50 6.25
Normal Gen 5 no pedigree collapse 218 3.125

What About Matching?

Inheritance and matching are different. Most of the time, two people are unlikely to share all of the DNA they inherited from a particular ancestor. Of course, inheriting through multiple paths increases the likelihood that at least some DNA from that ancestor is preserved and that it’s shared with other descendants.

Two people aren’t expected to match on all of the segments of DNA that they inherit from a particular ancestor. The closer in time the relationship, the more segments they will inherit from that ancestor, which increases the chances of matching on at least one or some segments.

Clearly, pedigree collapse affects matching. It’s most pronounced in closer relationships, but it may also be the only thing that has preserved that ONE matching segment in a more distant relationship.

So, how does pedigree collapse actually affect the likelihood of matching? What can we actually expect to see? Is there a name for this and a mathematical model to assist with calculations?

I’m so glad you asked! It’s called Coefficient of Relationship.

Coefficent of Relationship

My colleague, Diahan Southard, a scientist who writes at YourDNAGuide has authored two wonderful articles about calculating the statistical effects of pedigree collapse.

You can also read another article about the methodology of calculating coefficient of relationship, here, on WaybackMachine.

Diahan is a math whiz. I’m not, so I needed to devise something “quick and dirty” for my own personal use. I promised you a “cheat sheet,” so here’s the methodology.

Two Inheritance Paths – First and Third Cousins

Let’s look at an example where two people are both first cousins and third cousins because their grandparents were also first cousins.

Let’s calculate how these two people are related. They are first cousins and also third cousins.

When calculating the effects of pedigree collapse, we calculate the first relationship normally, then calculate the second relationship and add a portion of the result.

Here’s the math.

Using the Shared cM Project for the expected amount of shared DNA for both relationships, we’ve calculated the expected range for this pedigree collapse relationship.

Tying this back to degrees of relatedness.

Let’s look at ways to do Quick Calculations using the publicly available Shared cM charts and my composite tables, here.

Using Average Shared DNA

This first methodology uses average expected amount of shared, meaning matching, DNA. Please note, I’m not necessarily expecting you to DO this now, just read to follow.

Using Average Inherited DNA

Here’s a second method using average inherited DNA, meaning people wouldn’t be expected to match on all of the inherited DNA – just a portion.

You can’t always use the shared cM charts because all relationships aren’t represented, so you may need to use the amount of expected inherited DNA instead of shared DNA amounts.

Methodology Differences

Remember, none of these methodologies are foolproof because DNA inheritance is random. You may also have additional relationships that you’re aware of.

So, what’s the easiest method? Neither, actually. I’ve found an even easier method based on these proven methodologies.

Easy-Peasy Pedigree Collapse Shortcut Range Calculation in 4 Steps

Now that you understand the science and reasoning behind all of this, you can choose from multiple calculation methodologies after drawing a picture of the relevant tree.

You’re probably wondering, “What’s the easiest way to do this?”

  • These quick calculation methods are the easiest to work with for non-scientists and non-math whizzes. These are the calculations I use because, taking into account random recombination, you can’t do any better than get close.
  • Also, remember, if you’re dealing with double relationships, meaning double first cousins, you’ll need to take that into consideration, too.
  • If endogamy is involved, your matches will be higher yet, and you should use the highest calculations below because you need to be on the highest end of the range – and that may still not be high enough.

In these Easy-Peasy calculations, you calculate for the lowest, then the highest, and that’s your range. Please note that these are options, and truly, one size does not fit all.

  1. For the lowest end of the range, simply use the average of the highest relationship. In this case, that would be 1C, which is 866 cM. Remember that you may not share DNA with third cousins. 10% of third cousins don’t share any DNA, and 50% of fourth cousins don’t.
  2. For the highest end of the range, find the second relationship in the Shared cM chart, divide the average by half, and add to the value from the closest relationship. In this case, half of the 3C value of 76 is 38.
  3. Add 38 to 866 for the highest end of the range of 904.
  4. If there’s yet another path to ANY shared ancestor, add half that amount too to calculate the high end of the range – unless it’s 4C or more distant, then don’t add anything.

You can see that this easy-peasy range calculation for pedigree collapse compares very well to the more complex but still easy calculations.

  • Easy-peasy calculation: 866-904
  • Other calculation methods: 850-903
  • For this same relationship combination, Diahan’s statistical calculation was 850 cM.

Back to Genealogy

What’s the short story about how pedigree collapse affects genealogy?

Essentially, in close generations, meaning within a few generations of two first cousins marrying, descendants can expect to inherit and share significantly more DNA of the common ancestors, but not double the amount. As we move further away from those marriages in time, the effect becomes less pronounced and more difficult to detect. You can see that effect when calculating multiple paths where at the fourth cousin level, or more distant, those cousins have a 50% or greater possibility of not sharing DNA segments.

Of course, with multiple paths to the same ancestor, your chances of inheriting at least some segments from the common ancestor are increased because their DNA descends through multiple paths.

Today, close marriages are much less common and have been for several generations in many cultures, so we see fewer instances where pedigree collapse makes a significant difference.

Within a population or group of people, if pedigree collapse becomes common, meaning that there are multiple paths leading back to common ancestors, like our three-path example, DNA segments from the common ancestors are found among many people. Significant pedigree collapse becomes endogamy, especially if marriage outside of the group is difficult, impossible, or discouraged.

Normally, pedigree collapse is not recorded in actual records. It’s left to genealogists to discover those connections.

The exception, of course, is those wonderful Catholic parish records where the priest granted dispensations. Sometimes, that’s our only hint to earlier genealogy. In the case of the marriage of Marie-Josesphe LePrince to Jacques Forest, the priest wrote “dispense 3-3 consanguinity,” which tells us that they shared great-grandparents. It also tells us that their grandparents were siblings, that the bride and groom were second cousins, and that their children and descendants inherited an extra dose of DNA from their common great-grandparents.

How does that affect me today? Given that I’m their seventh-generation descendant – probably not at all. Of course, they are Acadian, and the Acadians are highly endogamous, which means I match many Acadians because all Acadians share the DNA of just a few founders, making it almost impossible to track segments to any particular ancestor. If it weren’t for endogamy, I would probably match few, if any, of their descendants.

Now, when you see those Catholic church dispensations or otherwise discover pedigree collapse, you can be really excited, because you understand the effects of pedigree collapse and how to calculate resulting matches! You might, just might, have retained a DNA segment from those ancestors because you inherited segments through multiple paths – increasing the probability that one survived.

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X Chromosome Master Class

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The X chromosome can be especially useful to genetic genealogists because it has a unique inheritance path. Thanks to that characteristic, some of the work of identifying your common ancestor is done just by simply HAVING an X match.

Unfortunately, X-DNA and X matching is both underutilized and somewhat misunderstood – in part because not all vendors utilize the X chromosome for matching.

The X chromosome has the capability of reaching further back in time and breaking down brick walls that might fall no other way.

Hopefully, you will read this article, follow along with your own DNA results and make important discoveries.

Let’s get started!

Who Uses the X Chromosome?

The X chromosome is autosomal in nature, meaning it recombines under some circumstances, but you only inherit your X chromosome from certain ancestors.

It’s important to understand why, and how to utilize the X chromosome for matching. In this article, I’ve presented this information in a variety of ways, including case studies, because people learn differently.

Of the four major testing vendors, only two provide X-DNA match results.

  • FamilyTreeDNA – provides X chromosome results and advanced matching capabilities including filtered X matching
  • 23andMe – provides X chromosome results, but not filtered X matching without downloading your results in spreadsheet format
  • Ancestry and MyHeritage do not provide X-DNA results but do include the X in your raw DNA file so you can upload to vendors who do provide X matching
  • GEDmatch – not a DNA testing vendor but a third-party matching database that provides X matching in addition to other tools

It’s worth noting at this point that X-DNA and mitochondrial DNA is not the same thing. I wrote about that, here. The source of this confusion is that the X chromosome and mitochondrial DNA are both associated in some way with descent from females – but they are very different and so is their inheritance path.

So, what is X-DNA and how does it work?

What is X-DNA?

Everyone inherits two copies of each of chromosomes 1-22, one copy of each chromosome from each of your parents.

That’s why DNA matching works and each match can be identified as “maternal” or “paternal,” depending on how your match is related to you. Each valid match (excluding identical by chance matches) will be related either maternally, or paternally, or sometimes, both.

Your 23rd chromosome is your sex determination chromosome and is inherited differently. Chromosome 23 is comprised of X and Y DNA.

Everyone inherits one copy of chromosome 23 from each parent.

  • Males inherit a Y chromosome from their father, which is what makes males male. They do not inherit an X chromosome from their father.
  • Males always inherit an X chromosome from their mother.
  • Females inherit an X chromosome from both parents, which is what makes them female. Females have two X chromosomes, and no Y chromosome.
Chromosome 23 Father Contributes Mother Contributes
Male Child Y chromosome X chromosome
Female Child X chromosome X chromosome

X-DNA and mitochondrial DNA are often confused, but they are not the same thing. In fact, they are completely different.

Mitochondrial DNA, in BOTH males and females is always inherited from only the mother and only descends from the direct matrilineal line, so only the mother’s mother’s mother’s direct line. X DNA can be inherited from a number of ancestors based on a specific inheritance path.

Everyone has both X-DNA AND mitochondrial DNA.

Because males don’t inherit an X chromosome from their father, X chromosome matching has a unique and specific pattern of descent which allows testers who match to immediately eliminate some potential common ancestors.

  • Males only inherit an X chromosome from their mother, which means they can only have legitimate X matches on their mother’s side of their tree.
  • Females, on the other hand, inherit an X chromosome from both their mother and father. Their father only has one X chromosome to contribute, so his daughter receives her paternal grandmother’s X chromosome intact.
  • Both males and females inherit their mother’s X chromosome just like any of the other 22 autosomes. I wrote about chromosomes, here.

However, the unique X chromosome inheritance path provides us with a fourth very useful type of DNA for genealogy, in addition to Y-DNA, mitochondrial and autosomal DNA.

For the vendors who provide X-matching, it’s included with your autosomal test and does not need to be purchased separately.

The Unique X Chromosome

The X chromosome, even though it is autosomal in nature, meaning it does recombine and divide in certain circumstances, is really its own distinct tool that is not equivalent to autosomal matching in the way we’re accustomed. We just need to learn about the message it’s delivering and how to interpret X matches.

FamilyTreeDNA is one of two vendors who utilizes X chromosome matching, along with 23andMe, which is another good reason to encourage your matches at other vendors to upload their DNA file to FamilyTreeDNA for free matching.

The four major vendors do include X-DNA results in their raw DNA download file, even if they don’t provide X-matching themselves. This means you can upload the results to either FamilyTreeDNA or GEDmatch where you can obtain X matches. I provided step-by-step download/upload instructions for each vendor here.

Let’s look how X matching is both different, and beneficial.

My X Chromosome Family Tree

We are going to build a simple case study. A case study truly is worth 1000 descriptions.

This fan chart of my family tree colorizes the X chromosome inheritance path. In this chart, males are colored blue and females pink, but the salient point is that I can inherit some portion of (or all of) a copy of my X chromosome from the colorized ancestors, and only those ancestors.

Because males don’t inherit an X chromosome from their father, they CANNOT inherit any portion of an X chromosome from their father’s ancestors.

Looking at my father’s half of the chart, at left, you see that I inherited an X chromosome from both of my parents, but my father only inherited an X chromosome from his mother, Ollie Bolton. His father’s portion of the tree is uncolored, so no X chromosome could have descended from his paternal ancestors to him. Therefore he could not pass any X chromosome segments to me from his paternal side – because he doesn’t have X DNA from his father.

Hence, I didn’t inherit an X chromosome from any of the people whose positions in the chart are uncolored, meaning I can only inherit an X chromosome from the pink or blue people.

Essentially any generational male to male, meaning father/son relationship is an X-DNA blocker.

I know positively that I inherited my paternal grandmother, Ollie Bolton’s entire X chromosome, because hers is the only X chromosome my father, in the fan chart above, had to give me. His entire paternal side of the fan chart is uncolored.

Men only ever inherit their X chromosome from their mother. The only exception to this is if a male has the rare genetic condition of Klinefelter Syndrome, also known as XXY. If you are an adult male, it’s likely that you’ll already know if you have Klinefelters, so that’s probably the last possibility you should consider if you appear to have paternal X matches, not the first.

Sometimes, men appear to have X matches on their father’s side, but (barring Klinefelter’s) this is impossible. Those matches must either be identical by chance, or somehow related in an unknown way on their mother’s side.

Everyone inherits an X chromosome from their mother that is some combination of the X from her father and mother. It’s possible to inherit all of your maternal grandmother or maternal grandfather’s X chromosome, meaning they did not recombine during meiosis.

Using DNA Painter as an X Tool

I use DNAPainter to track my matches and correlate segments with ancestors.

I paint my DNA segments for all my chromosomes at DNAPainter which provides me with a central tracking mechanism that is visual in nature and allows me to combine matches from multiple vendors who provide segment information. I provide step-by-step instructions for using DNAPainter, here.

This is my maternal X chromosome with my matches painted. I’ve omitted my matches’ names for privacy.

On the left side of the shaded grey column, those matches are from my maternal grandmother’s ancestors. On the right side, those matches are from my maternal grandfather’s ancestors.

The person in the grey column descends from unknown ancestors. In other words, I can tell that they descend from my maternal line, but I can’t (yet) determine through which of my two maternal grandparents.

There’s also an area to the right of the grey column where there are no matches painted, so I don’t know yet whether I inherited this portion of my X chromosome from my maternal grandmother or maternal grandfather.

The small darker pink columnar band is simply marking the centromere of the chromosome and does not concern us for this discussion.

Click on any image to enlarge

In this summary view of my paternal X chromosome, above, it appears that I may well have inherited my entire X chromosome from my paternal great-grandmother. We know, based on our inheritance rules that I clearly received my paternal grandmother’s X chromosome, because that’s all my father had to give me.

However, by painting my matches based on their ancestors, and selecting the summary view, you can see that most of my paternal X chromosome can be accounted for, with the exception of rather small regions with the red arrows.

It’s not terribly unusual for either a male or female to inherit their entire maternal X chromosome from one grandparent, or in this case, great-grandparent.

Of course, a male doesn’t inherit an X chromosome from their father, but a female can inherit her paternal X chromosome from either or both paternal grandparents.

Does Size Matter?

Generally speaking, an X match needs to be larger than a match on the other chromosomes to be considered genealogically equivalent in the same timeframe as other autosomal matches. This is due to:

  • The unique inheritance pattern, meaning fewer recombination events occurred.
  • The fact that X-DNA is NOT inherited from several lines.
  • The X chromosome has lower SNP density, meaning it contains fewer SNPs, so there are fewer possible locations to match when compared to the other chromosomes.

I know this equivalency requirement sounds negative, but it’s actually not. It means 7 cM (centimorgans) of DNA on the X chromosome will reach back further in time, so you may carry the DNA of an ancestor on the X chromosome that you no longer carry on other chromosomes. It may also mean that older segments remain larger. It’s actually a golden opportunity.

It sounds much more positive to say that a 16 cM X match for a female, or a 13 cM X match for a male is about the same as a 7 cM match for any other autosomal match in the same generation.

Of course, if the 7 cM match gets divided in the following generation, it has slipped below the matching threshold. If a 16 or 13 cM X match gets divided, it’s still a match. Plus, in some generations, if passed from father to daughter, it’s not divided or recombined. So a 7 cM X match may well be descended from ancestors further back in time.

X Chromosome Differences are Important!

Working with our great-great grandparent’s generation, we have 16 direct ancestors as illustrated in the earlier fan chart.

Given that females inherit from 8 X-chromosome ancestors in total, they are going to inherit an average of 45.25 cM of X-DNA from each of those ancestors. Females have two X chromosomes for a total length of 362 cM of X-DNA from both parents.

A male only has one X chromosome, 181 cM in length, so he will receive an average of 36.2 cM from each of 5 ancestors, and it’s all from his mother’s side.

In this chart, I’ve shown the total number of cMs for all of the autosomes, meaning chromosomes 1-22 and, separately, the X for males and females.

  • The average total cM for chromosomes 1-22 individually is 304 cM. (Yes, each chromosome is a different length, but that doesn’t matter for averages.)
  • That 304 cM can be inherited from any of 16 ancestors (in your great-grandparent’s generation)
  • The total number of cM on the X chromosomes for both parents for females totals 362
  • The total cM of X-DNA for males is 181 cM
  • The calculated average cM inherited for the X chromosome in the same generation is significantly different, shown in the bottom row.

The actual average for males and females for any ancestor on any random non-X chromosome (in the gg-grandparent generation) is still 19 cM. Due to the inheritance pattern of the X chromosome, the female X-chromosome average inheritance is 45.25 cM and the male average is 36.2 cM, significantly higher than the average of 19 cM that genetic genealogists have come to expect at this relationship distance on the other chromosomes, combined.

How Do I Interpret an X Match?

It’s important to remember when looking at X matching that you’re only looking at the amount of DNA from one chromosome. When you’re looking at any other matching amount, you’re looking at a total match across all chromosomes, as reported by that vendor. Vendors report total matching DNA differently.

  • The total amount of matching autosomal DNA does not include the X chromosome cMs at FamilyTreeDNA. X-DNA matching cMs are reported separately.
  • The total amount of matching autosomal DNA does include the X chromosome cMs in the total cM match at 23andMe
  • X-DNA is not used for matching or included in the match amount at either MyHeritage or Ancestry, but is included in the raw DNA data download files for all four vendors.
  • The total match amount shows the total for 22 (or 23) chromosomes, NOT just the X chromosome(s). That’s not apples to apples.

Therefore, an X match of 45 cM for a female or 36 for a male is NOT (necessarily) equivalent to a 19 cM non-X match. That 19 cM is the total for 22 chromosomes, while the X match amount is just for one chromosome.

You might consider a 20 cM match on the regular autosomes significant, but a 20 cM X-only match *could* be only roughly equivalent to a 10ish cM match on chromosomes 1-22 in the same generation. That’s the dog-leg inheritance pattern at work.

This is why FamilyTreeDNA does not report an X-only match if there is no other autosomal match. A 19 cM X match is not equivalent to a 19cM match on chromosomes 1-22. Not to mention, calculating relationships based on cM ranges becomes more difficult when the X is included.

However, the flip side is that because of the inheritance pattern of the X chromosome, that 19 cM match, if valid and not IBC, may well reach significantly further back in time than a regular autosomal matches. This can be particularly important for people seeking either Native or enslaved African ancestors for whom traditional records are elusive if they exist at all.

Critical Take-Away Messages

Here are the critical take-away messages:

  1. Because there are fewer ancestral lineages contributing to the tester’s X chromosome, the amount of X chromosomal DNA that a tester inherits from the ancestors who contribute to their X chromosome is increased substantially.
  2. The DNA of the contributing ancestors is more likely to be inherited, because there are fewer other possible contributing ancestors, meaning fewer recombination events or DNA divisions/recombinations.
  3. X-DNA is also more likely to be inherited because when passed from mother to son, it’s passed intact and not admixed with the DNA of the father.
  4. X matches cannot be compared equally to either percentages or cM amounts on any of the other chromosomes, or autosomal DNA in total, because X matching only reports the amount on one single chromosome, while your total cM match amount reports the amount of DNA that matches from all chromosomes (which includes the X at 23andMe).
  5. If you have X matches at 23andMe and/or FamilyTreeDNA, you can expect your total matching to be higher at 23andMe because they include the X matching cM in the total amount of shared DNA. FamilyTreeDNA provides the amount of X matching DNA separately, but not included in the total. MyHeritage and Ancestry do not include X matching DNA.

For clarity, at FamilyTreeDNA, you can see my shared DNA match with my mother. Of course, I match her on the total length of all my chromosomes, which is 3563 cM, the total Shared DNA for chromosomes 1-22. This includes all chromosomes except for the X chromosome which is reported separately at 181 cM. The longest contiguous block of shared DNA is 284 cM, the entire length of chromosome 1, the longest chromosome.

Because I’m a female, I match both parents on the full length of all 23 chromosomes, including 181 cM on both X chromosomes, respectively. Males will only match their mother on their X chromosome, meaning their total autosomal DNA match to their father, because the X is excluded, is 181 cM less than to their mother.

This difference in the amount of shared DNA with each parent, plus the differences in how DNA totals are reported by various vendors is also challenging for tools like DNAPainter’s Shared cM Tool which is based on the crowd sourced Shared cM Project that averages shared DNA numbers for known relationships at various vendors and translates those numbers into possible relationships for unknown matches.

Not all vendors report their total amount of shared DNA the same way. This is true for both X-DNA and half identical (HIR) versus fully identical (FIR) segments at 23andMe. This isn’t to say either approach is right or wrong, just to alert you to the differences.

Said Another Way

Let’s look at this another way.

If the average on any individual chromosome is 19 cMs for a relationship that’s 5 generations back in time. The average X-DNA for the same distance relationship is substantially more, which means that:

  • The X-DNA probably reaches further back in time than an equivalent relationship on any other autosome.
  • The X-DNA will have (probably) divided fewer times, and more DNA will descend from individual ancestors.
  • The inheritance path, meaning potential ancestors who contributed the X chromosomal DNA, is reduced significantly.

It’s challenging to draw equivalences when comparing X-DNA matching to the other chromosomes due to several variables that make interpretation difficult.

Based on the X-match size in comparison to the expected 19 cM single chromosome match at this genealogical distance, what is the comparable X-DNA segment size to the minimum 7 cM size generally accepted as valid on other chromosomes? What would be equal to a 7 cM segment on any other single random autosomal match, even though we know the inheritance probabilities are different and this isn’t apples to apples? Let’s pretend that it is.

This calculation presumes at the great-great-grandparent level that the 19 cM is in one single segment on a single chromosome. Now let’s divide 19 cM by 7 cM, which is 2.7, then divide the X amounts by the same number for the 7 cM equivalent of 16.75 cM for a female and 13.4 cM for a male.

When people say that you need a “larger X match to be equivalent to a regular autosomal match,” this is the phenomenon being referenced. Clearly a 7 cM X match is less relevant, meaning not equivalent, in the same generation as a 7 cM regular autosomal match.

Still, X matching compared to match amounts shown on the other chromosomes is never exact;u apples to apples because:

  • You’re comparing one X chromosome to the combined DNA amounts of many chromosomes.
  • The limited recombination path.
  • DNA from the other autosomes is less likely to be inherited from a specific ancestor.
  • The X chromosome has a lower SNP density than the other chromosomes, meaning fewer SNPs per cM.
  • The X-DNA may well reach further back in time because it has been divided less frequently.

Bottom Line

The X chromosome is different and holds clues that the other autosomes can’t provide.

Don’t dismiss X matches even if you can’t identify a common ancestor. Given the inheritance path, and the reduced number of divisions, your X-DNA may descend from an ancestor further back in time. I certainly would NOT dismiss X matches with smaller cMs than the 13 and 16 shown above, even though they are considered “equivalent” in the same generation.

X chromosome matching can’t really be equated to matching on the other chromosomes. They are two distinct tools, so they can’t be interpreted identically.

Different vendors treat the X chromosome differently, making comparison challenging.

  • 23andMe includes not only the X chromosome in their cM total, but doubles the Fully Identical Regions (FIR) when people, such as full siblings, share the same DNA from both parents. I wrote about that here.
  • Ancestry does not include the X in their cM match calculations.
  • Neither does MyHeritage.
  • FamilyTreeDNA shows an X match only when it’s accompanied by a match on another chromosome.

The Shared cM Project provides an average of all of the data input by crowdsourcing from all vendors, by relationship, which means that the cM values for some relationships are elevated when compared to the same relationship or even same match were it to be reported from a different vendor.

The Best Part!

The X chromosome inheritance pattern means that you’re much more likely to carry some amount of a contributing ancestor’s X-DNA than on any other chromosome.

  • X-DNA may well be “older” because it’s not nearly as likely to be divided, given that there are fewer opportunities for recombination.
  • When you’re tracking your X-DNA back in your tree, whenever you hit a male, you get an automatic “bump” back a generation to his mother. It’s like the free bingo X-DNA square!
  • You can immediately eliminate many ancestors as your most recent common ancestor (MRCA) with an X-DNA match.
  • Because X-DNA reaches further back in time, sometimes you match people who descend from common ancestors further back in time as well.

If you match someone on multiple segments, if one of those matching segments is X-DNA, that segment is more likely to descend from a different ancestor than the segments on chromosomes 1-22. I’ve found many instances where an X match descends from a different ancestor than matching DNA segments on the autosomes. Always evaluate X matches carefully.

Sometimes X-DNA is exactly what you need to solve a mystery.

Ok, now let’s step through how to use X-DNA in a real-life example.

Using X DNA to Solve a Mystery

Let’s say that I have a 30 cM X match with a male.

  • I know immediately that our most recent common ancestor (MRCA) is on HIS mother’s side.
  • I know, based on my fan chart, which ancestral lines are eliminated in my tree. I’ve immediately narrowed the ancestors from 16 to 5 on his side and 16 to 8 on my side.
  • Two matching males is even easier, because you know immediately that the common ancestor must be on both of their mother’s sides, with only 5 candidate lines each at the great-great-grandparent generation.

Female to female matches are slightly more complex, but there are still several immediately eliminated lines each. That means you’ve already eliminated roughly half of the possible relationships by matching another female on their X chromosome.

In this match with a female second cousin, I was able to identify who she was via our common ancestor based on the X chromosome path. In this chart, I’m showing the relevant halves of her chart at left (paternal), and mine (maternal), side by side.

I added blockers on her chart and mine too.

As it turns out, we both inherited most of our X chromosome from our great-grandparents, marked above with the black stars.

Several lines are blocked, and my grandfather’s X chromosome is not a possibility because the common ancestor is my maternal grandmother’s parents. My grandfather is not one of her ancestors.

Having identified this match as my closest relative (other than my mother) to descend on my mother’s maternal side, I was able to map that portion of my X chromosome to my great-grandparents Nora Kirsch and Curtis Benjamin Lore.

My X Chromosome at DNA Painter

Here’s my maternal X chromosome at DNAPainter and how I utilized chromosome painting to push the identification of the ancestors whose X chromosome I inherited back an additional two generations.

Using that initial X chromosome match with my second cousin, shown by the arrow at bottom of the graphic, I mapped a large segment of my maternal X chromosome to my maternal great-grandparents.

By viewing the trees of subsequent X maternal matches, I was then able to push those common segments, shown painted directly above that match with the same color, back another two generations, to Joseph Hill, born in 1790, and Nabby Hall. I was able to do that based on the fact that other matches descend from Joseph and Nabby through different children, meaning we all triangulate on that common segment. I wrote about triangulation at DNAPainter, here.

I received no known X-DNA from my great-grandmother, Nora Kirsch, although a small portion of my X chromosome is still unassigned in yellow as “Uncertain.”

I received a small portion of my maternal X chromosome, in magenta, at left, from my maternal great-great-grandparents, John David Miller and Margaret Lentz.

The X chromosome is a powerful tool and can reach far back in time.

In some cases, the X, and other chromosomes can be inherited intact from one grandparent. I could have inherited my mother’s entire copy of her mother’s, or her father’s X chromosome based on random recombination, or not. As it turns out, I didn’t, and I know that because I’ve mapped my chromosomes to identify my ancestors based on common ancestors with my matches.

X-DNA Advanced Matches at FamilyTreeDNA

At FamilyTreeDNA, the Advanced Matches tab includes the ability to search for X matches, either within the entire database, or within specific projects. I find the project selection to be particularly useful.

For example, within the Claxton project, my father’s maternal grandmother’s line, I recognize my match, Joy, which provides me an important clue as to the possible common ancestor(s) of our shared segments.

Joy’s tree shows that her 4-times great-grandparents are my 3-times great-grandparents, meaning we are 4th cousins once removed and share 17 cM of DNA on our X chromosome across two segments.

Don’t be deceived by the physical appearance of “size” on your chromosomes. The first segment that spans the centromere, or “waist” of the chromosome, above, is 10.29 cM, and the smaller segment at right is 7.02 cM. SNPs are not necessarily evenly distributed along chromosomes.

Remember, an X or other autosomal match doesn’t necessarily mean the entire match is contained in one segment so long as it’s large enough to be divided in two parts and survive the match threshold.

It’s worth noting that Joy and I actually share at least two different, unrelated ancestral lines, so I need to look at Joy’s blocked lines to see if one of those common ancestral lines is not a possibility for our X match. It’s important to evaluate all possible ancestors, plus the inheritance path to eliminate any lineage that involves a father to son inheritance on the X chromosome.

Last but not least, you may match on your X chromosome through a different ancestor than on other chromosomes. Every matching segment has its own individual history. It’s not safe to assume.

Now, take a look at your X chromosome matches at FamilyTreeDNA, 23andMe, and GedMatch. What will you discover?

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DNA: In Search of…Signs of Endogamy

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21

This is the fourth in our series of articles about searching for unknown close family members, specifically; parents, grandparents, or siblings. However, these same techniques can be applied by genealogists to ancestors further back in time as well.

In this article, we discuss endogamy – how to determine if you have it, from what population, and how to follow the road signs.

After introductions, we will be covering the following topics:

  • Pedigree collapse and endogamy
  • Endogamous groups
  • The challenge(s) of endogamy
  • Endogamy and unknown close relatives (parents, grandparents)
  • Ethnicity and Populations
  • Matches
  • AutoClusters
  • Endogamous Relationships
  • Endogamous DNA Segments
  • “Are Your Parents Related?” Tool
  • Surnames
  • Projects
  • Locations
  • Y DNA, Mitochondrial DNA, and Endogamy
  • Endogamy Tools Summary Tables
    • Summary of Endogamy Tools by Vendor
    • Summary of Endogamous Populations Identified by Each Tool
    • Summary of Tools to Assist People Seeking Unknown Parents and Grandparents

What Is Endogamy and Why Does It Matter?

Endogamy occurs when a group or population of people intermarry among themselves for an extended period of time, without the introduction of many or any people from outside of that population.

The effect of this continual intermarriage is that the founders’ DNA simply gets passed around and around, eventually in small segments.

That happens because there is no “other” DNA to draw from within the population. Knowing or determining that you have endogamy helps make sense of DNA matching patterns, and those patterns can lead you to unknown relatives, both close and distant.

This Article

This article serves two purposes.

  • This article is educational and relevant for all researchers. We discuss endogamy using multiple tools and examples from known endogamous people and populations.
  • In order to be able to discern endogamy when we don’t know who our parents or grandparents are, we need to know what signs and signals to look for, and why, which is based on what endogamy looks like in people who know their heritage.

There’s no crystal ball – no definitive “one-way” arrow, but there are a series of indications that suggest endogamy.

Depending on the endogamous population you’re dealing with, those signs aren’t always the same.

If you’re sighing now, I understand – but that’s exactly WHY I wrote this article.

We’re covering a lot of ground, but these road markers are invaluable diagnostic tools.

I’ve previously written about endogamy in the articles:

Let’s start with definitions.

Pedigree Collapse and Endogamy

Pedigree collapse isn’t the same as endogamy. Pedigree collapse is when you have ancestors that repeat in your tree.

In this example, the parents of our DNA tester are first cousins, which means the tester shares great-grandparents on both sides and, of course, the same ancestors from there on back in their tree.

This also means they share more of those ancestors’ DNA than they would normally share.

John Smith and Mary Johnson are both in the tree twice, in the same position as great-grandparents. Normally, Tester Smith would carry approximately 12.5% of each of his great-grandparents’ DNA, assuming for illustration purposes that exactly 50% of each ancestor’s DNA is passed in each generation. In this case, due to pedigree collapse, 25% of Tester Smith’s DNA descends from John Smith, and another 25% descends from Mary Johnson, double what it would normally be. 25% is the amount of DNA contribution normally inherited from grandparents, not great-grandparents.

While we may find first cousin marriages a bit eyebrow-raising today, they were quite common in the past. Both laws and customs varied with the country, time, social norms, and religion.

Pedigree Collapse and Endogamy is NOT the Same

You might think that pedigree collapse and endogamy is one and the same, but there’s a difference. Pedigree collapse can lead to endogamy, but it takes more than one instance of pedigree collapse to morph into endogamy within a population. Population is the key word for endogamy.

The main difference is that pedigree collapse occurs with known ancestors in more recent generations for one person, while endogamy is longer-term and systemic in a group of people.

Picture a group of people, all descended from Tester Smith’s great-grandparents intermarrying. Now you have the beginnings of endogamy. A couple hundred or a few hundred years later, you have true endogamy.

In other words, endogamy is pedigree collapse on a larger scale – think of a village or a church.

My ancestors’ village of Schnait, in Germany, is shown above in 1685. One church and maybe 30 or 40 homes. According to church and other records, the same families had inhabited this village, and region, for generations. It’s a sure bet that both pedigree collapse and endogamy existed in this small community.

If pedigree collapse happens over and over again because there are no other people within the community to marry, then you have endogamy. In other words, with endogamy, you assuredly DO have historical pedigree collapse, generally back in time, often before you can identify those specific ancestors – because everyone descends from the same set of founders.

Endogamy Doesn’t Necessarily Indicate Recent Pedigree Collapse

With deep, historic endogamy, you don’t necessarily have recent pedigree collapse, and in fact, many people do not. Jewish people are a good example of this phenomenon. They shared ancestors for hundreds or thousands of years, depending on which group we are referring to, but in recent, known, generations, many Jewish people aren’t related. Still, their DNA often matches each other.

The good news is that there are telltale signs and signals of endogamy.

The bad news is that not all of these are obvious, meaning as an aid to people seeking clues about unknown close relatives, and other “signs” aren’t what they are believed to be.

Let’s step through each endogamy identifier, or “hint,” and then we will review how we can best utilize this information.

First, let’s take a look at groups that are considered to be endogamous.

Endogamous Groups

Jewish People – Specifically groups that were isolated from other groups of Jewish (and other) people; Ashkenazi (Germany, Northern France, and diaspora), Sephardic (Spanish, Iberia, and diaspora), Mizrahi (Israel, Middle Eastern, and diaspora,) Ethiopian Jews, and possibly Jews from other locations such as Mountain Jews from Kazakhstan and the Caucasus.

Acadians – Descendants of about 60 French families who settled in “Acadia” beginning about 1604, primarily on the island of Nova Scotia, and intermarried among themselves and with the Mi’kmaq people. Expelled by the English in 1755, they were scattered in groups to various diasporic regions where they continued to intermarry and where their descendants are found today. Some Acadians became the Cajuns of Louisiana.

Anabaptist Protestant Faiths – Amish, Mennonite, and Brethren (Dunkards) and their offshoots are Protestant religious sects founded in Europe in the 14th, 15th, and 16th centuries on the principle of baptizing only adults or people who are old enough to choose to follow the faith, or rebaptizing people who had been previously baptized as children. These Anabaptist faiths tend to marry within their own group or church and often expel those who marry outside of the faith. Many emigrated to the American colonies and elsewhere, seeking religious freedom. Occasionally those groups would locate in close proximity and intermarry, but not marry outside of other Anabaptist denominations.

Native American (Indigenous) People – all indigenous peoples found in North and South America before European colonization descended from a small number of original founders who probably arrived at multiple times.

Indigenous Pacific Islanders – Including indigenous peoples of Australia, New Zealand, and Hawaii prior to colonization. They are probably equally as endogamous as Native American people, but I don’t have specific examples to share.

Villages – European or other villages with little inflow or whose residents were restricted from leaving over hundreds of years.

Other groups may have significant multiple lines of pedigree collapse and therefore become endogamous over time. Some people from Newfoundland, French Canadians, and Mormons (Church of Jesus Christ of Latter-Day Saints) come to mind.

Endogamy is a process that occurs over time.

Endogamy and Unknown Relatives

If you know who your relatives are, you may already know you’re from an endogamous population, but if you’re searching for close relatives, it’s helpful to be able to determine if you have endogamous heritage, at least in recent generations.

If you know nothing about either parent, some of these tools won’t help you, at least not initially, but others will. However, as you add to your knowledge base, the other tools will become more useful.

If you know the identity of one parent, this process becomes at least somewhat easier.

In future articles, we will search specifically for parents and each of your four grandparents. In this article, I’ll review each of the diagnostic tools and techniques you can use to determine if you have endogamy, and perhaps pinpoint the source.

The Challenge

People with endogamous heritage are related in multiple, unknown ways, over many generations. They may also be related in known ways in recent generations.

If both of your parents share the SAME endogamous culture or group of relatives:

  • You may have significantly more autosomal DNA matches than people without endogamy, unless that group of people is under-sampled. Jewish people have significantly more matches, but Native people have fewer due to under-sampling.
  • You may experience a higher-than-normal cM (centiMorgan) total for estimated relationships, especially more distant relationships, 3C and beyond.
  • You will have many matches related to you on both your maternal and paternal sides.
  • Parts of your autosomal DNA will be the same on both your mother’s and father’s sides, meaning your DNA will be fully identical in some locations. (I’ll explain more in a minute.)

If either (or both) of your parents are from an endogamous population, you:

  • Will, in some cases, carry identifying Y and mitochondrial DNA that points to a specific endogamous group. This is true for Native people, can be true for Jewish people and Pacific Islanders, but is not true for Anabaptist people.

One Size Does NOT Fit All

Please note that there is no “one size fits all.”

Each or any of these tools may provide relevant hints, depending on:

  • Your heritage
  • How many other people have tested from the relevant population group
  • How many close or distant relatives have tested
  • If your parents share the same heritage
  • Your unique DNA inheritance pattern
  • If your parents, individually, were fully endogamous or only partly endogamous, and how far back generationally that endogamy occurred

For example, in my own genealogy, my maternal grandmother’s father was Acadian on his father’s side. While I’m not fully endogamous, I have significantly more matches through that line proportionally than on my other lines.

I have Brethren endogamy on my mother’s side via her paternal grandmother.

Endogamous ancestors are shown with red stars on my mother’s pedigree chart, above. However, please note that her maternal and paternal endogamous ancestors are not from the same endogamous population.

However, I STILL have fewer matches on my mother’s side in total than on my father’s side because my mother has recent Dutch and recent German immigrants which reduces her total number of matches. Neither of those lines have had as much time to produce descendants in the US, and Europe is under-sampled when compared with the US where more people tend to take DNA tests because they are searching for where they came from.

My father’s ancestors have been in the US since it was a British Colony, and I have many more cousins who have tested on his side than mother’s.

If you looked at my pedigree chart and thought to yourself, “that’s messy,” you’d be right.

The “endogamy means more matches” axiom does not hold true for me, comparatively, between my parents – in part because my mother’s German and Dutch lines are such recent immigrants.

The number of matches alone isn’t going to tell this story.

We are going to need to look at several pieces and parts for more information. Let’s start with ethnicity.

Ethnicity and Populations

Ethnicity can be a double-edged sword. It can tell you exactly nothing you couldn’t discern by looking in the mirror, or, conversely, it can be a wealth of information.

Ethnicity reveals the parts of the world where your ancestors originated. When searching for recent ancestors, you’re most interested in majority ethnicity, meaning the 50% of your DNA that you received from each of your parents.

Ethnicity results at each vendor are easy to find and relatively easy to understand.

This individual at FamilyTreeDNA is 100% Ashkenazi Jewish.

If they were 50% Jewish, we could then estimate, and that’s an important word, that either one of their parents was fully Jewish, and not the other, or that two of their grandparents were Jewish, although not necessarily on the same side.

On the other hand, my mother’s ethnicity, shown below, has nothing remarkable that would point to any majority endogamous population, yet she has two.

The only hint of endogamy from ethnicity would be her ~1% Americas, and that isn’t relevant for finding close relatives. However, minority ancestry is very relevant for identifying Native ancestors, which I wrote about, here.

You can correlate or track your ethnicity segments to specific ancestors, which I discussed in the article, Native American & Minority Ancestors Identified Using DNAPainter Plus Ethnicity Segments, here.

Since I wrote that article, FamilyTreeDNA has added the feature of ethnicity or population Chromosome Painting, based on where each of your populations fall on your chromosomes.

In this example on chromosome 1, I have European ancestry (blue,) except for the pink Native segment, which occurs on the following segment in the same location on my mother’s chromosome 1 as well.

Both 23andMe, and FamilyTreeDNA provide chromosome painting AND the associated segment information so you can identify the relevant ancestors.

Ancestry is in the process of rolling out an ethnicity painting feature, BUT, it has no segment or associated matching information. While it’s interesting eye candy, it’s not terribly useful beyond the ethnicity information that Ancestry already provides. However, Jonny Perl at DNAPainter has devised a way to estimate Ancestry’s start and stop locations, here. Way to go Jonny!

Now all you need to do is convince your Ancestry matches to upload their DNA file to one of the three databases, FamilyTreeDNA, MyHeritage, and GEDMatch, that accept transfers, aka uploads. This allows matching with segment data so that you can identify who matches you on that segment, track your ancestors, and paint your ancestral segments at DNAPainter.

I provided step-by-step instructions, here, for downloading your raw DNA file from each vendor in order to upload the file to another vendor.

Ethnicity Sides

Three of the four DNA testing vendors, 23andMe, FamilyTreeDNA, and recently, Ancestry, attempt to phase your ethnicity DNA, meaning to assign it to one parental “side” or the other – both in total and on each chromosome.

Here’s Ancestry’s SideView, where your DNA is estimated to belong to parent 1 and parent 2. I detailed how to determine which side is which, here, and while that article was written specifically pertaining to Ancestry’s SideView, the technique is relevant for all the vendors who attempt to divide your DNA into parents, a technique known as phasing.

I say “attempt” because phasing may or may not be accurate, meaning the top chromosome may not always be parent 1, and the bottom chromosome may not always be chromosome 2.

Here’s an example at 23andMe.

See the two yellow segments. They are both assigned as Native. I happen to know one is from the mother and one is from the father, yet they are both displayed on the “top” chromosome, which one would interpret to be the same parent.

I am absolutely positive this is not the case because this is a close family member, and I have the DNA of the parent who contributed the Native segment on chromosome 1, on the top chromosome. That parent does not have a Native segment on chromosome 2 to contribute. So that Native segment had to be contributed by the other parent, but it’s also shown on the top chromosome.

The DNA segments circled in purple belong together on the same “side” and were contributed to the tester by the same parent. The Native segment on chromosome 2 abuts a purple African segment, suggesting perhaps that the ancestor who contributed that segment was mixed between those ethnicities. In the US, that suggests enslavement.

The other African segments, circled, are shown on the second chromosome in each pair.

To be clear, parent 1 is not assigned by the vendors to either mother or father and will differ by person. Your parent 1, or the parent on the top chromosome may be your mother and another person’s parent 1 may be their father.

As shown in this example, parents can vary by chromosome, a phenomenon known as “strand swap.” Occasionally, the DNA can even be swapped within a chromosome assignment.

You can, however, get an idea of the division of your DNA at any specific location. As shown above, you can only have a maximum of two populations of DNA on any one chromosome location.

In our example above, this person’s majority ancestry is European (blue.) On each chromosome where we find a minority segment, the opposite chromosome in the same location is European, meaning blue.

Let’s look at another example.

At FamilyTreeDNA, the person whose ethnicity painting is shown below has a Native American (pink) ancestor on their father’s side. FamilyTreeDNA has correctly phased or identified their Native segments as all belonging to the second chromosome in each pair.

Looking at chromosome 18, for example, most of their father’s chromosome is Native American (pink). The other parent’s chromosome is European (dark blue) at those same locations.

If one of the parents was of one ethnicity, and the other parent is a completely different ethnicity, then one bar of each chromosome would be all pink, for example, and one would be entirely blue, representing the other ethnicity.

Phasing ethnicity or populations to maternal and paternal sides is not foolproof, and each chromosome is phased individually.

Ethnicity can, in some cases, give you a really good idea of what you’re dealing with in terms of heritage and endogamy.

If someone had an Ashkenazi Jewish father and European mother, for example, one copy of each chromosome would be yellow (Ashkenazi Jewish), and one would be blue (European.)

However, if each of their parents were half European Jewish and half European (not Jewish), then their different colored segments would be scattered across their entire set of chromosomes.

In this case, both of the tester’s parents are mixed – European Jewish (green) and Western Europe (blue.) We know both parents are admixed from the same two populations because in some locations, both parents contributed blue (Western Europe), and in other locations, both contributed Jewish (green) segments.

Both MyHeritage and Ancestry provide a secondary tool that’s connected to ethnicity, but different and generally in more recent times.

Ancestry’s DNA Communities

While your ethnicity may not point to anything terribly exciting in terms of endogamy, Genetic Communities might. Ancestry says that a DNA Community is a group of people who share DNA because their relatives recently lived in the same place at the same time, and that communities are much smaller than ethnicity regions and reach back only about 50-300 years.

Based on the ancestors’ locations in the trees of me and my matches, Ancestry has determined that I’m connected to two communities. In my case, the blue group is clearly my father’s line. The orange group could be either parent, or even a combination of both.

My endogamous Brethren could be showing up in Maryland, Pennsylvania, and Ohio, but it’s uncertain, in part, because my father’s ancestral lines are found in Virginia, West Virginia, and Maryland too.

These aren’t useful for me, but they may be more useful for fully endogamous people, especially in conjunction with ethnicity.

My Acadian cousin’s European ethnicity isn’t informative.

However, viewing his DNA Communities puts his French heritage into perspective, especially combined with his match surnames.

I wrote about DNA Communities when it was introduced with the name Genetic Communities, here.

MyHeritage’s Genetic Groups

MyHeritage also provides a similar feature that shows where my matches’ ancestors lived in the same locations as mine.

One difference, though, is that testers can adjust their ethnicity results confidence level from high, above, to low, below where one of my Genetic Groups overlaps my ethnicity in the Netherlands.

You can also sort your matches by Genetic Groups.

The results show you not only who is in the group, but how many of your matches are in that group too, which provides perspective.

I wrote about Genetic Groups, here.

Next, let’s look at how endogamy affects your matches.

Matches

The number of matches that a person has who is from an entirely endogamous community and a person with no endogamy may be quite different.

FamilyTreeDNA provides a Family Matching feature that triangulates your matches and assigns them to your paternal or maternal side by using known matches that you have linked to their profile cards in your tree. You must link people for the Family Matching feature known as “bucketing” to be enabled.

The people you link are then processed for shared matches on the same chromosome segment(s). Triangulated individuals are then deposited in your maternal, paternal, and both buckets.

Obviously, your two parents are the best people to link, but if they haven’t tested (or uploaded their DNA file from another vendor) and you have other known relatives, link them using the Family Tree tab at the top of your personal page.

I uploaded my Ancestry V4 kit to use as an example for linking. Let’s pretend that’s my sister. If I had not already linked my Ancestry V4 kit to “my sister’s” profile card, I’d want to do that and link other known individuals the same way. Just drag and drop the match to the correct profile card.

Note that a full or half sibling will be listed as such at FamilyTreeDNA, but an identical twin will show as a potential parent/child match to you. You’re much more likely to find a parent than an identical twin, but just be aware.

I’ve created a table of FamilyTreeDNA bucketed match results, by category, comparing the number of matches in endogamous categories with non-endogamous.

Total Matches Maternal Matches Paternal Matches Both % Both % DNA Unassigned
100% Jewish 34,637 11,329 10,416 4,806 13.9 23.3
100% Jewish 32,973 10,700 9,858 4,606 14 23.7
100% Jewish 32,255 9,060 10,970 3,892 12 25.8
75% Jewish 24,232 11,846 Only mother linked Only mother linked Only mother linked
100% Acadian 8093 3826 2299 1062 13 11
100% Acadian 7828 3763 1825 923 11.8 17
Not Endogamous 6760 3845 1909 13 0.19 14.5
Not Endogamous 7723 1470 3317 6 0.08 38
100% Native American 1,115 Unlinked Unlinked Unlinked
100% Native American 885 290 Unknown Can’t calculate without at least one link on both sides

The 100% Jewish, Acadian, and Not Endogamous testers both have linked their parents, so their matches, if valid (meaning not identical by chance, which I discussed here,) will match them plus one or the other parent.

One person is 75% Jewish and has only linked their Jewish mother.

The Native people have not tested their parents, and the first Native person has not linked anyone in their tree. The second Native person has only linked a few maternal matches, but their mother has not tested. They are seeking their father.

It’s very difficult to find people who are fully Native as testers. Furthermore, Native people are under-sampled. If anyone knows of fully Native (or other endogamous) people who have tested and linked their parents or known relatives in their trees, and will allow me to use their total match numbers anonymously, please let me know.

As you can see, Jewish, Acadian, and Native people are 100% endogamous, but many more Jewish people than Native people have tested, so you CAN’T judge endogamy by the total number of matches alone.

In fact, in order:

  • Fully Jewish testers have about 4-5 times as many matches as the Acadian and Non-endogamous testers
  • Acadian and Non-endogamous testers have about 5-6 times as many matches as the Native American testers
  • Fully Jewish people have about 30 times more matches than the Native American testers

If a person’s endogamy with a particular population is only on their maternal or paternal side, they won’t have a significant number of people related to both sides, meaning few people will fall into the “Both” bucket. People that will always be found in the ”Both” bucket are full siblings and their descendants, along with descendants of the tester, assuming their match is linked to their profiles in the tester’s tree.

In the case of our Jewish testers, you can easily see that the “Both” bucket is very high. The Acadians are also higher than one would reasonably expect without endogamy. A non-endogamous person might have a few matches on both sides, assuming the parents are not related to each other.

A high number of “Both” matches is a very good indicator of endogamy within the same population on both parents’ sides.

The percentage of people who are assigned to the “Both” bucket is between 11% and 14% in the endogamous groups, and less than 1% in the non-endogamous group, so statistically not relevant.

As demonstrated by the Native people compared to the Jewish testers, the total number of matches can be deceiving.

However, being related to both parents, as indicated by the “Both” bucket, unless you have pedigree collapse, is a good indicator of endogamy.

Of course, if you don’t know who your relatives are, you can’t link them in your tree, so this type of “hunt” won’t generally help people seeking their close family members.

However, you may notice that you’re matching people PLUS both of their parents. If that’s the case, start asking questions of those matches about their heritage.

A very high number of total matches, as compared to non-endogamous people, combined with some other hints might well point to Jewish heritage.

I included the % DNA Unassigned category because this category, when both parents are linked, is the percentage of matches by chance, meaning the match doesn’t match either of the tester’s parents. All of the people with people listed in “Both” categories have linked both of their parents, not just maternal and paternal relatives.

Matching Location at MyHeritage

MyHeritage provides a matching function by location. Please note that it’s the location of the tester, but that may still be quite useful.

The locations are shown in the most-matches to least-matches order. Clicking on the location shows the people who match you who are from that location. This would be the most useful in situations where recent immigration has occurred. In my case, my great-grandfather from the Netherlands arrived in the 1860s, and my German ancestors arrived in the 1850s. Neither of those groups are endogamous, though, unless it would be on a village level.

AutoClusters

Let’s shift to Genetic Affairs, a third-party tool available to everyone.

Using their AutoCluster function, Genetic Affairs clusters your matches together who match both each other and you.

This is an example of the first few clusters in my AutoCluster. You can see that I have several colored clusters of various sizes, but none are huge.

Compare that to the following endogamous cluster, sample courtesy of EJ Blom at Genetic Affairs.

If your AutoCluster at Genetic Affairs looks something like this, a huge orange blob in the upper left hand corner, you’re dealing with endogamy.

Please also note that the size of your cluster is also a function of both the number of testers and the match threshold you select. I always begin by using the defaults. I wrote about using Genetic Affairs, here.

If you tested at or transferred to MyHeritage, they too license AutoClusters, but have optimized the algorithm to tease out endogamous matches so that their Jewish customers, in particular, don’t wind up with a huge orange block of interrelated people.

You won’t see the “endogamy signature” huge cluster in the corner, so you’re less likely to be able to discern endogamy from a MyHeritage cluster alone.

The commonality between these Jewish clusters at MyHeritage is that they all tend to be rather uniform in size and small, with lots of grey connecting almost all the blocks.

Grey cells indicate people who match people in two colored groups. In other words, there is often no clear division in clusters between the mother’s side and the father’s side in Jewish clusters.

In non-endogamous situations, even if you can’t identify the parents, the clusters should still fall into two sides, meaning a group of clusters for each parent’s side that are not related to each other.

You can read more about Genetic Affairs clusters and their tools, here. DNAGedcom.com also provides a clustering tool.

Endogamous Relationships

Endogamous estimated relationships are sometimes high. Please note the word, “sometimes.”

Using the Shared cM Project tool relationship chart, here, at DNAPainter, people with heavy endogamy will discover that estimated relationships MAY be on the high side, or the relationships may, perhaps, be estimated too “close” in time. That’s especially true for more distant relationships, but surprisingly, it’s not always true. The randomness of inheritance still comes into play, and so do potential unknown relatives. Hence, the words “may” are bolded and underscored.

Unfortunately, it’s often stated as “conventional wisdom” that Jewish matches are “always” high, and first cousins appear as siblings. Let’s see what the actual data says.

At DNAPainter, you can either enter the amount of shared DNA (cM), or the percent of shared DNA, or just use the chart provided.

I’ve assembled a compilation of close relationships in kits that I have access to or from people who were generous enough to share their results for this article.

I’ve used Jewish results, which is a highly endogamous population, compared with non-endogamous testers.

The “Jewish Actual” column reports the total amount of shared DNA with that person. In other words, someone to their grandparent. The Average Range is the average plus the range from DNAPainter. The Percent Difference is the % difference between the actual number and the DNAPainter average.

You’ll see fully Jewish testers, at left, matching with their family members, and a Non-endogamous person, at right, matching with their same relative.

Relationship Jewish Actual Percent Difference than Average Average -Range Non-endogamous Actual Percent Difference than Average
Grandparent 2141 22 1754 (984-2482) 1742 <1 lower
Grandparent 1902 8.5 1754 (984-2482) 1973 12
Sibling 3039 16 2613 (1613-3488) 2515 3.5 lower
Sibling 2724 4 2613 (1613-3488) 2761 5.5
Half-Sibling 2184 24 1759 (1160-2436) 2127 21
Half-Sibling 2128 21 1759 (1160-2436) 2352 34
Aunt/Uncle 2066 18.5 1741 (1201-2282) 1849 6
Aunt/Uncle 2031 16.5 1741 (1201-2282) 2097 20
1C 1119 29 866 (396-1397) 959 11
1C 909 5 866 (396-1397) 789 9 lower
1C1R 514 19 433 (102-980) 467 8
1C1R 459 6 433 (102-980) 395 9 lower

These totals are from FamilyTreeDNA except one from GEDMatch (one Jewish Half-sibling).

Totals may vary by vendor, even when matching with the same person. 23andMe includes the X segments in the total cMs and also counts fully identical segments twice. MyHeritage imputation seems to err on the generous side.

However, in these dozen examples:

  • You can see that the Jewish actual amount of DNA shared is always more than the average in the estimate.
  • The red means the overage is more than 100 cM larger.
  • The percentage difference is probably more meaningful because 100 cM is a smaller percentage of a 1754 grandparent connection than compared to a 433 cM 1C1R.

However, you can’t tell anything about endogamy by just looking at any one sample, because:

  • Some of the Non-Endogamous matches are high too. That’s just the way of random inheritance.
  • All of the actual Jewish match numbers are within the published ranges, but on the high side.

Furthermore, it can get more complex.

Half Endogamous

I requested assistance from Jewish genealogy researchers, and a lovely lady, Sharon, reached out, compiled her segment information, and shared it with me, granting permission to share with you. A HUGE thank you to Sharon!

Sharon is half-Jewish via one parent, and her half-sibling is fully Jewish. Their half-sibling match to each other at Ancestry is 1756 cM with a longest segment of 164 cM.

How does Jewish matching vary if you’re half-Jewish versus fully Jewish? Let’s look at 21 people who match both Sharon and her fully Jewish half-sibling.

Sharon shared the differences in 21 known Jewish matches with her and her half-sibling. I’ve added the Relationship Estimate Range from DNAPainter and colorized the highest of the two matches in yellow. Bolding in the total cM column shows a value above the average range for that relationship.

Total Matching cMs is on the left, with Longest Segment on the right.

While this is clearly not a scientific study, it is a representative sample.

The fully Jewish sibling carries more Jewish DNA, which is available for other Jewish matches to match as a function of endogamy (identical by chance/population), so I would have expected the fully Jewish sibling to match most if not all Jewish testers at a higher level than the half-Jewish sibling.

However, that’s not universally what we see.

The fully Jewish sibling is not always the sibling with the highest number of matches to the other Jewish testers, although the half-Jewish tester has the larger “Longest Segment” more often than not.

Approximately two-thirds of the time (13/21), the fully Jewish person does have a higher total matching cM, but about one-third of the time (8/21), the half-Jewish sibling has a higher matching cM.

About one-fourth of the time (5/21), the fully Jewish sibling has the longest matching segment, and about two-thirds of the time (13/21), the half-Jewish sibling does. In three cases, or about 14% of the time, the longest segment is equal which may indicate that it’s the same segment.

Because of endogamy, Jewish matches are more likely to have:

  • Larger than average total cM for the specific relationship
  • More and smaller matching segments

However, as we have seen, neither of those are definitive, nor always true. Jewish matches and relationships are not always overestimated.

Ancestry and Timber

Please note that Ancestry downweights some matches by removing some segments using their Timber algorithm. Based on my matches and other accounts that I manage, Ancestry does not downweight in the 2-3rd cousin category, which is 90 cM and above, but they do begin downweighting in the 3-4th cousin category, below 90 cM, where my “Extended Family” category begins.

If you’ve tested at Ancestry, you can check for yourself.

By clicking on the amount of DNA you share with your match on your match list at Ancestry, shown above, you will be taken to another page where you will be able to view the unweighted shared DNA with that match, meaning the amount of DNA shared before the downweighting and removal of some segments, shown below.

Given the downweighting, and the information in the spreadsheet provided by Sharon, it doesn’t appear that any of those matches would have been in a category to be downweighted.

Therefore, for these and other close matches, Timber wouldn’t be a factor, but would potentially be in more distant matches.

Endogamous Segments

Endogamous matches tend to have smaller and more segments. Small amounts of matching DNA tend to skew the total DNA cM upwards.

How and why does this happen?

Ancestral DNA from further back in time tends to be broken into smaller segments.

Sometimes, especially in endogamous situations, two smaller segments, at one time separated from each other, manage to join back together again and form a match, but the match is only due to ancestral segments – not because of a recent ancestor.

Please note that different vendors have different minimum matching cM thresholds, so smaller matches may not be available at all vendors. Remember that factors like Timber and imputation can affect matching as well.

Let’s take a look at an example. I’ve created a chart where two ancestors have their blue and pink DNA broken into 4 cM segments.

They have children, a blue child and a pink child, and the two children, shown above, each inherited the same blue 4 cM segment and the same pink 4 cM segment from their respective parents. The other unlabeled pink and blue segments are not inherited by these two children, so those unlabeled segments are irrelevant in this example.

The parents may have had other children who inherited those same 4 cM labeled pink and blue segments as well, and if not, the parents’ siblings were probably passing at least some of the same DNA down to their descendants too.

The blue and pink children had children, and their children had children – for several generations.

Time passed, and their descendants became an endogamous community. Those pink and blue 4 cM segments may at some time be lost during recombination in the descendants of each of their children, shown by “Lost pink” and “Lost blue.”

However, because there is only a very limited amount of DNA within the endogamous community, their descendants may regain those same segments again from their “other parent” during recombination, downstream.

In each generation, the DNA of the descendant carrying the original blue or pink DNA segment is recombined with their partner. Given that the partners are both members of the same endogamous community, the two people may have the same pink and/or blue DNA segments. If one parent doesn’t carry the pink 4 cM segment, for example, their offspring may receive that ancestral pink segment from the other parent.

They could potentially, and sometimes do, receive that ancestral segment from both parents.

In our example, the descendants of the blue child, at left, lost the pink 4 cM segment in generation 3, but a few generations later, in generation 11, that descendant child inherited that same pink 4 cM segment from their other parent. Therefore, both the 4 cM blue and 4 cM pink segments are now available to be inherited by the descendants in that line. I’ve shown the opposite scenario in the generational inheritance at right where the blue segment is lost and regained.

Once rejoined, that pink and blue segment can be passed along together for generations.

The important part, though, is that once those two segments butt up against each other again during recombination, they aren’t just two separate 4 cM segments, but one segment that is 8 cM long – that is now equal to or above the vendors’ matching threshold.

This is why people descended from endogamous populations often have the following matching characteristics:

  • More matches
  • Many smaller segment matches
  • Their total cM is often broken into more, smaller segments

What does more, smaller segments, look like, exactly?

More, Smaller Segments

All of our vendors except Ancestry have a chromosome browser for their customers to compare their DNA to that of their matches visually.

Let’s take a look at some examples of what endogamous and non-endogamous matches look like.

For example, here’s a screen shot of a random Jewish second cousin match – 298 cM total, divided into 12 segments, with a longest segment of 58 cM,

A second Jewish 2C with 323 cM total, across 19 segments, with a 69 cM longest block.

A fully Acadian 2C match with 600 cM total, across 27 segments, with a longest segment of 69 cM.

A second Acadian 2C with 332 cM total, across 20 segments, with a longest segment of 42 cM.

Next, a non-endogamous 2C match with 217 cM, across 7 segments, with a longest segment of 72 cM.

Here’s another non-endogamous 2C example, with 169 shared cM, across 6 segments, with a longest segment of 70 cM.

Here’s the second cousin data in a summary table. The take-away from this is the proportion of total segments

Tester Population Total cM Longest Block Total Segments
Jewish 2C 298 58 12
Jewish 2C 323 69 19
Acadian 2C 600 69 27
Acadian 2C 332 42 20
Non-endogamous 2C 217 72 7
Non-endogamous 2C 169 70 6

You can see more examples and comparisons between Native American, Jewish and non-endogamous DNA individuals in the article, Concepts – Endogamy and DNA Segments.

I suspect that a savvy mathematician could predict endogamy based on longest block and total segment information.

Lara Diamond, a mathematician, who writes at Lara’s Jewnealogy might be up for this challenge. She just published compiled matching and segment information in her Ashkenazic Shared DNA Survey Results for those who are interested. You can also contribute to Laura’s data, here.

Endogamy, Segments, and Distant Relationships

While not relevant to searching for close relatives, heavily endogamous matches 3C and more distant, to quote one of my Jewish friends, “dissolve into a quagmire of endogamy and are exceedingly difficult to unravel.”

In my own Acadian endogamous line, I often simply have to label them “Acadian” because the DNA tracks back to so many ancestors in different lines. In other words, I can’t tell which ancestor the match is actually pointing to because the same DNA segments or segments is/are carried by several ancestors and their descendants due to founder effect.

The difference with the Acadians is that we can actually identify many or most of them, at least at some point in time. As my cousin, Paul LeBlanc, once said, if you’re related to one Acadian, you’re related to all Acadians. Then he proceeded to tell me that he and I are related 137 different ways. My head hurts!

It’s no wonder that endogamy is incredibly difficult beyond the first few generations when it turns into something like multi-colored jello soup.

“Are Your Parents Related?” Tool

There’s another tool that you can utilize to determine if your parents are related to each other.

To determine if your parents are related to each other, you need to know about ROH, or Runs of Homozygosity (ROH).

ROH means that the DNA on both strands or copies of the same chromosome is identical.

For a few locations in a row, ROH can easily happen just by chance, but the longer the segment, the less likely that commonality occurs simply by chance.

The good news is that you don’t need to know the identity of either of your parents. You don’t need either of your parent’s DNA tests – just your own. You’ll need to upload your DNA file to GEDmatch, which is free.

Click on “Are your parents related?”

GEDMatch analyzes your DNA to see if any of your DNA, above a reasonable matching threshold, is identical on both strands, indicating that you inherited the exact same DNA from both of your parents.

A legitimate match, meaning one that’s not by chance, will include many contiguous matching locations, generally a minimum of 500 SNPs or locations in a row. GEDmatch’s minimum threshold for identifying identical ancestral DNA (ROH) is 200 cM.

Here’s my result, including the graphic for the first two chromosomes. Notice the tiny green bars that show identical by chance tiny sliver segments.

I have no significant identical DNA, meaning my parents are not related to each other.

Next, let’s look at an endogamous example where there are small, completely identical segments across a person’s chromosome

This person’s Acadian parents are related to each other, but distantly.

Next, let’s look at a Jewish person’s results.

You’ll notice larger green matching ROH, but not over 200 contiguous SNPs and 7 cM.

GEDMatch reports that this Jewish person’s parents are probably not related within recent generations, but it’s clear that they do share DNA in common.

People whose parents are distantly related have relatively small, scattered matching segments. However, if you’re seeing larger ROH segments that would be large enough to match in a genealogical setting, meaning multiple greater than 7 cM and 500 SNPs,, you may be dealing with a different type of situation where cousins have married in recent generations. The larger the matching segments, generally, the closer in time.

Blogger Kitty Cooper wrote an article, here, about discovering that your parents are related at the first cousin level, and what their GEDMatch “Are Your Parents Related” results look like.

Let’s look for more clues.

Surnames

There MAY be an endogamy clue in the surnames of the people you match.

Viewing surnames is easier if you download your match list, which you can do at every vendor except Ancestry. I’m not referring to the segment data, but the information about your matches themselves.

I provided instructions in the recent article, How to Download Your DNA Match Lists and Segment Files, here.

If you suspect endogamy for any reason, look at your closest matches and see if there is a discernable trend in the surnames, or locations, or any commonality between your matches to each other.

For example, Jewish, Acadian, and Native surnames may be recognizable, as may locations.

You can evaluate in either or both of two ways:

  • The surnames of your closest matches. Closest matches listed first will be your default match order.
  • Your most frequently occurring surnames, minus extremely common names like Smith, Jones, etc., unless they are also in your closest matches. To utilize this type of matching, sort the spreadsheet in surname order and then scan or count the number of people with each surname.

Here are some examples from our testers.

Jewish – Closest surname matches.

  • Roth
  • Weiss
  • Goldman
  • Schonwald
  • Levi
  • Cohen
  • Slavin
  • Goodman
  • Sender
  • Trebatch

Acadian – Closest surname matches.

  • Bergeron
  • Hebert
  • Bergeron
  • Marcum
  • Muise
  • Legere
  • Gaudet
  • Perry
  • Verlander
  • Trombley

Native American – Closest surname matches.

  • Ortega
  • Begay
  • Valentine
  • Hayes
  • Montoya
  • Sun Bear
  • Martin
  • Tsosie
  • Chiquito
  • Yazzie

You may recognize these categories of surnames immediately.

If not, Google is your friend. Eliminate common surnames, then Google for a few together at a time and see what emerges.

The most unusual surnames are likely your best bets.

Projects

Another way to get some idea of what groups people with these surnames might belong to is to enter the surname in the FamilyTreeDNA surname search.

Go to the main FamilyTreeDNA page, but DO NOT sign on.

Scroll down until you see this image.

Type the surname into the search box. You’ll see how many people have tested with that surname, along with projects where project administrators have included that surname indicating that the project may be of interest to at least some people with that surname.

Here’s a portion of the project list for Cohen, a traditional Jewish surname.

These results are for Muise, an Acadian surname.

Clicking through to relevant surname projects, and potentially contacting the volunteer project administrator can go a very long way in helping you gather and sift information. Clearly, they have an interest in this topic.

For example, here’s the Muise surname in the Acadian AmerIndian project. Two great hints here – Acadian heritage and Halifax, Nova Scotia.

Repeat for the balance of surnames on your list to look for commonalities, including locations on the public project pages.

Locations

Some of the vendor match files include location information. Each person on your match list will have the opportunity at the vendor where they tested to include location information in a variety of ways, either for their ancestors or themselves.

Where possible, it’s easiest to sort or scan the download file for this type of information.

Ancestry does not provide or facilitate a match list, but you can still create your own for your closest 20 or 30 matches in a spreadsheet.

MyHeritage provides common surname and ancestral location information for every match. How cool is that!

Y DNA, Mitochondrial DNA, and Endogamy

Haplogroups for both Y and mitochondrial DNA can indicate and sometimes confirm endogamy. In other cases, the haplogroup won’t help, but the matches and their location information just might.

FamilyTreeDNA is the only vendor that provides Y DNA and mitochondrial DNA tests that include highly granular haplogroups along with matches and additional tools.

23andMe provides high-level haplogroups which may or may not be adequate to pinpoint a haplogroup that indicates endogamy.

Of course, only males carry Y DNA that tracks to the direct paternal (surname) line, but everyone carries their mother’s mitochondrial DNA that represents their mother’s mother’s mother’s, or direct matrilineal line.

Some haplogroups are known to be closely associated with particular ethnicities or populations, like Native Americans, Pacific Islanders, and some Jewish people.

Haplogroups reach back in time before genealogy and can give us a sense of community that’s not available by either looking in the mirror or through traditional records.

This Native American man is a member of high-level haplogroup Q-M242. However, some men who carry this haplogroup are not Native, but are of European or Middle Eastern origin.

I entered the haplogroup in the FamilyTreeDNA Discover tool, which I wrote about, here.

Checking the information about this haplogroup reveals that their common ancestor descended from an Asian man about 30,000 years ago.

The migration path in the Americans explains why this person would have an endogamous heritage.

Our tester would receive a much more refined haplogroup if he upgraded to the Big Y test at FamilyTreeDNA, which would remove all doubt.

However, even without additional testing, information about his matches at FamilyTreeDNA may be very illuminating.

The Q-M242 Native man’s Y DNA matches men with more granular haplogroups, shown above, at left. On the Haplogroup Origins report, you can see that these people have all selected the “US (Native American)” country option.

Another useful tool would be to check the public Y haplotree, here, and the public mitochondrial tree here, for self-reported ancestor location information for a specific haplogroup.

Here’s an example of mitochondrial haplogroup A2 and a few subclades on the public mitochondrial tree. You can see that the haplogroup is found in Mexico, the US (Native,) Canada, and many additional Caribbean, South, and Central American countries.

Of course, Y DNA and mitochondrial DNA (mtDNA) tell a laser-focused story of one specific line, each. The great news, if you’re seeking information about your mother or father, the Y is your father’s direct paternal (surname) line, and mitochondrial is your mother’s direct matrilineal line.

Y and mitochondrial DNA results combined with ethnicity, autosomal matching, and the wide range of other tools that open doors, you will be able to reveal a great deal of information about whether you have endogamous heritage or not – and if so, from where.

I’ve provided a resource for stepping through and interpreting your Y DNA results, here, and mitochondrial DNA, here.

Discover for Y DNA Only

If you’re a female, you may feel left out of Y DNA testing and what it can tell you about your heritage. However, there’s a back door.

You can utilize the Y DNA haplogroups of your closest autosomal matches at both FamilyTreeDNA and 23andMe to reveal information

Haplogroup information is available in the download files for both vendors, in addition to the Family Finder table view, below, at FamilyTreeDNA, or on your individual matches profile cards at both 23andMe and FamilyTreeDNA.

You can enter any Y DNA haplogroup in the FamilyTreeDNA Discover tool, here.

You’ll be treated to:

  • Your Haplogroup Story – how many testers have this haplogroup (so far), where the haplogroup is from, and the haplogroup’s age. In this case, the haplogroup was born in the Netherlands about 250 years ago, give or take 200 years. I know that it was 1806 or earlier based on the common ancestor of the men who tested.
  • Country Frequency – heat map of where the haplogroup is found in the world.
  • Notable Connections – famous and infamous (this haplogroup’s closest notable person is Leo Tolstoy).
  • Migration Map – migration path out of Africa and through the rest of the world.
  • Ancient Connections – ancient burials. His closest ancient match is from about 1000 years ago in Ukraine. Their shared ancestor lived about 2000 years ago.
  • Suggested Projects – based on the surname, projects that other matches have joined, and haplogroups.
  • Scientific Details – age estimates, confidence intervals, graphs, and the mutations that define this haplogroup.

I wrote about the Discover tool in the article, FamilyTreeDNA DISCOVER Launches – Including Y DNA Haplogroup Ages.

Endogamy Tools Summary Tables

Endogamy is a tough nut sometimes, especially if you’re starting from scratch. In order to make this topic a bit easier and to create a reference tool for you, I’ve created three summary tables.

  • Various endogamy-related tools available at each vendor which will or may assist with evaluating endogamy
  • Tools and their ability to detect endogamy in different groups
  • Tools best suited to assist people seeking information about unknown parents or grandparents

Summary of Endogamy Tools by Vendor

Please note that GEDMatch is not a DNA testing vendor, but they accept uploads and do have some tools that the testing vendors do not.

 Tool 23andMe Ancestry FamilyTreeDNA MyHeritage GEDMatch
Ethnicity Yes Yes Yes Yes Use the vendors
Ethnicity Painting Yes + segments Yes, limited Yes + segments Yes
Ethnicity Phasing Yes Partial Yes No
DNA Communities No Yes No No
Genetic Groups No No No Yes
Family Matching aka Bucketing No No Yes No
Chromosome Browser Yes No Yes Yes Yes
AutoClusters Through Genetic Affairs No Through Genetic Affairs Yes, included Yes, with subscription
Match List Download Yes, restricted # of matches No Yes Yes Yes
Projects No No Yes No
Y DNA High-level haplogroup only No Yes, full haplogroup with Big Y, matching, tools, Discover No
Mitochondrial DNA High-level haplogroup only No Yes, full haplogroup with mtFull, matching, tools No
Public Y Tree No No Yes No
Public Mito Tree No No Yes No
Discover Y DNA – public No No Yes No
ROH No No No No Yes

Summary of Endogamous Populations Identified by Each Tool

The following chart provides a guideline for which tools are useful for the following types of endogamous groups. Bolded tools require that both parents be descended from the same endogamous group, but several other tools give more definitive results with higher amounts of endogamy.

Y and mitochondrial DNA testing are not affected by admixture, autosomal DNA or anything from the “other” parent.

Tool Jewish Acadian Anabaptist Native Other/General
Ethnicity Yes No No Yes Pacific Islander
Ethnicity Painting Yes No No Yes Pacific Islander
Ethnicity Phasing Yes, if different No No Yes, if different Pacific Islander, if different
DNA Communities Yes Possibly Possibly Yes Pacific Islander
Genetic Groups Yes Possibly Possibly Yes Pacific Islander
Family Matching aka Bucketing Yes Yes Possibly Yes Pacific Islander
Chromosome Browser Possibly Possibly Yes, once segments or ancestors identified Possibly Pacific Islander, possibly
Total Matches Yes, compared to non-endogamous No No No No, unknown
AutoClusters Yes Yes Uncertain, probably Yes Pacific Islander
Estimated Relationships High Not always Sometimes No Sometimes Uncertain, probably
Relationship Range High Possibly, sometimes Possibly Possibly Possibly Pacific Islander, possibly
More, Smaller Segments Yes Yes Probably Yes Pacific Islander, probably
Parents Related Some but minimal Possibly Uncertain Probably similar to Jewish Uncertain, Possibly
Surnames Probably Probably Probably Not Possibly Possibly
Locations Possibly Probably Probably Not Probably Probably Pacific Islander
Projects Probably Probably Possibly Possibly Probably Pacific Islander
Y DNA Yes, often Yes, often No Yes Pacific Islander
Mitochondrial DNA Yes, often Sometimes No Yes Pacific Islander
Y public tree Probably not alone No No Yes Pacific Islander
MtDNA public tree Probably not No No Yes Pacific Islander
Y DNA Discover Yes Possibly Probably not, maybe projects Yes Pacific Islander

Summary of Endogamy Tools to Assist People Seeking Unknown Parents and Grandparents

This table provides a summary of when each of the various tools can be useful to:

  • People seeking unknown close relatives
  • People who already know who their close relatives are, but are seeking additional information or clues about their genealogy

I considered rating these on a 1 to 10 scale, but the relative usefulness of these tools is dependent on many factors, so different tools will be more or less useful to different people.

For example, ethnicity is very useful if someone is admixed from different populations, or even 100% of a specific endogamous population. It’s less useful if the tester is 100% European, regardless of whether they are seeking close relatives or not. Conversely, even “vanilla” ethnicity can be used to rule out majority or recent admixture with many populations.

Tools Unknown Close Relative Seekers Known Close Relatives – Enhance Genealogy
Ethnicity Yes, to identify or rule out populations Yes
Ethnicity Painting Yes, possibly, depending on population Yes, possibly, depending on population
Ethnicity Phasing Yes, possibly, depending on population Yes, possibly, depending on population
DNA Communities Yes, possibly, depending on population Yes, possibly, depending on population
Genetic Groups Possibly, depending on population Possibly, depending on population
Family Matching aka Bucketing Not if parents are entirely unknown, but yes if one parent is known Yes
Chromosome Browser Unlikely Yes
AutoClusters Yes Yes, especially at MyHeritage if Jewish
Estimated Relationships High Not No
Relationship Range High Not reliably No
More, Smaller Segments Unlikely Unlikely other than confirmation
Match List Download Yes Yes
Surnames Yes Yes
Locations Yes Yes
Projects Yes Yes
Y DNA Yes, males only, direct paternal line, identifies surname lineage Yes, males only, direct paternal line, identifies and correctly places surname lineage
Mitochondrial DNA Yes, both sexes, direct matrilineal line only Yes, both sexes, direct matrilineal line only
Public Y Tree Yes for locations Yes for locations
Public Mito Tree Yes for locations Yes for locations
Discover Y DNA Yes, for heritage information Yes, for heritage information
Parents Related – ROH Possibly Less useful

Acknowledgments

A HUGE thank you to several people who contributed images and information in order to provide accurate and expanded information on the topic of endogamy. Many did not want to be mentioned by name, but you know who you are!!!

If you have information to add, please post in the comments.

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Top Ten RootsTech 2022 DNA Sessions + All DNA Session Links

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The official dates of RootsTech 2022 were March 3-5, but the sessions and content in the vendor booths are still available. I’ve compiled a list of the sessions focused on DNA, with web links on the RootsTech YouTube channel

YouTube reports the number of views, so I was able to compile that information as of March 8, 2022.

I do want to explain a couple of things to add context to the numbers.

Most speakers recorded their sessions, but a few offered live sessions which were recorded, then posted later for participants to view. However, there have been glitches in that process. While the sessions were anticipated to be available an hour or so later, that didn’t quite happen, and a couple still aren’t posted. I’m sure the presenters are distressed by this, so be sure to watch those when they are up and running.

The Zoom rooms where participants gathered for the live sessions were restricted to 500 attendees. The YouTube number of views does not include the number of live viewers, so you’ll need to add an additional number, up to 500.

When you see a number before the session name, whether recorded or live, that means that the session is part of a series. RootsTech required speakers to divide longer sessions into a series of shorter sessions no longer than 15-20 minutes each. The goal was for viewers to be able to watch the sessions one after the other, as one class, or separately, and still make sense of the content. Let’s just say this was the most challenging thing I’ve ever done as a presenter.

For recorded series sessions, these are posted as 1, 2 and 3, as you can see below with Diahan Southard’s sessions. However, with my live session series, that didn’t happen. It looks like my sessions are a series, but when you watch them, parts 1, 2 and 3 are recorded and presented as one session. Personally, I’m fine with this, because I think the information makes a lot more sense this way. However, it makes comparisons difficult.

This was only the second year for RootsTech to be virtual and the conference is absolutely HUGE, so live and learn. Next year will be smoother and hopefully, at least partially in-person too.

When I “arrived” to present my live session, “Associating Autosomal DNA Segments With Ancestors,” my lovely moderator, Rhett, told me that they were going to livestream my session to the RootsTech page on Facebook as well because they realized that the 500 Zoom seat limit had been a problem the day before with some popular sessions. I have about 9000 views for that session and more than 7,400 of them are on the RootsTech Facebook page – and that was WITHOUT any advance notice or advertising. I know that the Zoom room was full in addition. I felt kind of strange about including my results in the top ten because I had that advantage, but I didn’t know quite how to otherwise count my session. As it turns out, all sessions with more than 1000 views made it into the top ten so mine would have been there one way or another. A big thank you to everyone who watched!

I hope that the RootsTech team notices that the most viewed session is the one that was NOT constrained by the 500-seat limited AND was live-streamed on Facebook. Seems like this might be a great way to increase session views for everyone next year. Hint, hint!!!

I also want to say a huge thank you to all of the presenters for producing outstanding content. The sessions were challenging to find, plus RootsTech is always hectic, even virtually. So, I know a LOT of people will want to view these informative sessions, now that you know where to look and have more time. Please remember to “like” the session on YouTube as a way of thanking your presenter.

With 140 DNA-focused sessions available, you can watch a new session, and put it to use, every other day for the next year! How fun is that! You can use this article as your own playlist.

Please feel free to share this article with your friends and genealogy groups so everyone can learn more about using DNA for genealogy.

Ok, let’s look at the top 10. Drum roll please…

Top 10 Most Viewed RootsTech Sessions

Session Title Presenter YouTube Link Views
1 1. Associating Autosomal DNA Segments With Ancestors Roberta Estes (live) https://www.youtube.com/watch?v=_IHSCkNnX48

 

 ~9000: 1019 + 500 live viewers + 7,400+ Facebook
2 1. What to Do with Your DNA Test Results in 2022 (part 1 of 3) Diahan Southard https://www.youtube.com/watch?v=FENAKAYLXX4 7428
3 Who Is FamilyTreeDNA? FamilyTreeDNA – Bennett Greenspan https://www.youtube.com/watch?v=MHFtwoatJ-A 2946
4 2. What to Do with Your DNA Test Results in 2022 (part 2 of 3) Diahan Southard https://www.youtube.com/watch?v=mIllhtONhlI 2448
5 Latest DNA Painter Releases DNAPainter Jonny Perl (live) https://www.youtube.com/watch?v=iLBThU8l33o 2230 + live viewers
6 DNA Painter Introduction DNAPainter – Jonny Perl https://www.youtube.com/watch?v=Rpe5LMPNmf0 1983
7 3. What to Do with Your DNA Test Results in 2022 (part 3 of 3) Diahan Southard https://www.youtube.com/watch?v=hemY5TuLmGI 1780
8 The Tree of Mankind Age Estimates Paul Maier https://www.youtube.com/watch?v=jjkL8PWAEwk 1638
9 A Sneak Peek at FamilyTreeDNA Coming Attractions FamilyTreeDNA (live) https://www.youtube.com/watch?v=K9sKqNScvnE 1270 + live viewers

 
10 Extending Time Horizons with DNA Rob Spencer (live) https://www.youtube.com/watch?v=wppXD1Zz2sQ 1037 + live viewers

 

All DNA-Focused Sessions

I know you’ll find LOTS of goodies here. Which ones are your favorites?

  Session Presenter YouTube Link Views
1 Estimating Relationships by Combining DNA from Multiple Siblings Amy Williams https://www.youtube.com/watch?v=xs1U0ohpKSA 201
2 Overview of HAPI-DNA.org Amy Williams https://www.youtube.com/watch?v=FjNiJgWaBeQ 126
3 How do AncestryDNA® Communities help tell your story? | Ancestry® Ancestry https://www.youtube.com/watch?v=EQNpUxonQO4 183

 
4 AncestryDNA® 201 Ancestry – Crista Cowan https://www.youtube.com/watch?v=lbqpnXloM5s

 

 494
5 Genealogy in a Minute: Increase Discoveries by Attaching AncestryDNA® Results to Family Tree Ancestry – Crista Cowan https://www.youtube.com/watch?v=iAqwSCO8Pvw 369
6 AncestryDNA® 101: Beginner’s Guide to AncestryDNA® | Ancestry® Ancestry – Lisa Elzey https://www.youtube.com/watch?v=-N2usCR86sY 909
7 Hidden in Plain Sight: Free People of Color in Your Family Tree Cheri Daniels https://www.youtube.com/watch?v=FUOcdhO3uDM 179
8 Finding Relatives to Prevent Hereditary Cancer ConnectMyVariant – Dr. Brian Shirts https://www.youtube.com/watch?v=LpwLGgEp2IE 63
9 Piling on the chromosomes Debbie Kennett https://www.youtube.com/watch?v=e14lMsS3rcY 465
10 Linking Families With Rare Genetic Condition Using Genealogy Deborah Neklason https://www.youtube.com/watch?v=b94lUfeAw9k 43
11 1. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=FENAKAYLXX4 7428
12 1. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=hemY5TuLmGI 1780
13 2. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=mIllhtONhlI 2448
14 DNA Testing For Family History Diahan Southard https://www.youtube.com/watch?v=kCLuOCC924s 84

 
15 Understanding Your DNA Ethnicity Estimate at 23andMe Diana Elder

 

 https://www.youtube.com/watch?v=xT1OtyvbVHE 66
16 Understanding Your Ethnicity Estimate at FamilyTreeDNA Diana Elder https://www.youtube.com/watch?v=XosjViloVE0 73
17 DNA Monkey Wrenches Katherine Borges https://www.youtube.com/watch?v=Thv79pmII5M 245
18 Advanced Features in your Ancestral Tree and Fan Chart DNAPainter – Jonny Perl https://www.youtube.com/watch?v=4u5Vf13ZoAc 425
19 DNA Painter Introduction DNAPainter – Jonny Perl https://www.youtube.com/watch?v=Rpe5LMPNmf0 1983
20 Getting Segment Data from 23andMe DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=8EBRI85P3KQ 134
21 Getting segment data from FamilyTreeDNA DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=rWnxK86a12U 169
22 Getting segment data from Gedmatch DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=WF11HEL8Apk 163
23 Getting segment data from Geneanet DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=eclj8Ap0uK4 38
24 Getting segment data from MyHeritage DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=9rGwOtqbg5E 160
25 Inferred Chromosome Mapping: Maximize your DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=tzd5arHkv64 688
26 Keeping track of your genetic family tree in a fan chart DNAPainter – Jonny Perl https://www.youtube.com/watch?v=W3Hcno7en94 806

 
27 Mapping a DNA Match in a Chromosome Map DNAPainter – Jonny Perl https://www.youtube.com/watch?v=A61zQFBWaiY 423
28 Setting up an Ancestral Tree and Fan Chart and Exploring Tree Completeness DNAPainter – Jonny Perl https://www.youtube.com/watch?v=lkJp5Xk1thg 77
29 Using the Shared cM Project Tool to Evaluate DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=vxhn9l3Dxg4 763
30 Your First Chromosome Map: Using your DNA Matches to Link Segments to Ancestors DNAPainter – Jonny Perl https://www.youtube.com/watch?v=tzd5arHkv64 688
31 DNA Painter for absolute beginners DNAPainter (Jonny Perl) https://www.youtube.com/watch?v=JwUWW4WHwhk 1196
32 Latest DNA Painter Releases DNAPainter (live) https://www.youtube.com/watch?v=iLBThU8l33o 2230 + live viewers
33 Unraveling your genealogy with DNA segment networks using AutoSegment from Genetic Affairs Evert-Jan Blom https://www.youtube.com/watch?v=rVpsJSqOJZI

 

 162
34 Unraveling your genealogy with genetic networks using AutoCluster Evert-Jan Blom https://www.youtube.com/watch?v=ZTKSz_X7_zs 201

 

 
35 Unraveling your genealogy with reconstructed trees using AutoTree & AutoKinship from Genetic Affairs Evert-Jan Blom https://www.youtube.com/watch?v=OmDQoAn9tVw 143
36 Research Like a Pro with DNA – A Genealogist’s Guide to Finding and Confirming Ancestors with DNA Family Locket Genealogists https://www.youtube.com/watch?v=NYpLscJJQyk 183
37 How to Interpret a DNA Network Graph Family Locket Genealogists – Diana Elder https://www.youtube.com/watch?v=i83WRl1uLWY 393
38 Find and Confirm Ancestors with DNA Evidence Family Locket Genealogists – Nicole Dyer https://www.youtube.com/watch?v=DGLpV3aNuZI 144
39 How To Make A DNA Network Graph Family Locket Genealogists – Nicole Dyer https://www.youtube.com/watch?v=MLm_dVK2kAA 201
40 Create A Family Tree With Your DNA Matches-Use Lucidchart To Create A Picture Worth A Thousand Words Family Locket Genealogists – Robin Wirthlin https://www.youtube.com/watch?v=RlRIzcW-JI4 270
41 Charting Companion 7 – DNA Edition Family Tree Maker https://www.youtube.com/watch?v=k2r9rkk22nU 316

 
42 Family Finder Chromosome Browser: How to Use FamilyTreeDNA https://www.youtube.com/watch?v=w0_tgopBn_o 750

 

 
43 FamilyTreeDNA: 22 Years of Breaking Down Brick Walls FamilyTreeDNA https://www.familysearch.org/rootstech/session/familytreedna-22-years-of-breaking-down-brick-walls Not available
44 Review of Autosomal DNA, Y-DNA, & mtDNA FamilyTreeDNA  – Janine Cloud https://www.youtube.com/watch?v=EJoQVKxgaVY 77
45 Who Is FamilyTreeDNA? FamilyTreeDNA – Bennett Greenspan https://www.youtube.com/watch?v=MHFtwoatJ-A 2946
46 Part 1: How to Interpret Y-DNA Results, A Walk Through the Big Y FamilyTreeDNA – Casimir Roman https://www.youtube.com/watch?v=ra1cjGgvhRw 684

 
47 Part 2: How to Interpret Y-DNA Results, A Walk Through the Big Y FamilyTreeDNA – Casimir Roman https://www.youtube.com/watch?v=CgqcjBD6N8Y

 

 259
48 Big Y-700: A Brief Overview FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=IefUipZcLCQ 96
49 Mitochondrial DNA & The Million Mito Project FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=5Zppv2uAa6I 179
50 Mitochondrial DNA: What is a Heteroplasmy FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=ZeGTyUDKySk 57
51 Y-DNA Big Y: A Lifetime Analysis FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=E6NEU92rpiM 154
52 Y-DNA: How SNPs Are Added to the Y Haplotree FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=CGQaYcroRwY 220
53 Family Finder myOrigins: Beginner’s Guide FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=VrJNpSv8nlA 88
54 Mitochondrial DNA: Matches Map & Results for mtDNA FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=YtA1j01MOvs 190
55 Mitochondrial DNA: mtDNA Mutations Explained FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=awPs0cmZApE 340

 
56 Y-DNA: Haplotree and SNPs Page Overview FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=FOuVhoMD-hw 432
57 Y-DNA: Understanding the Y-STR Results Page FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=gCeZz1rQplI 148
58 Y-DNA: What Is Genetic Distance? FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=qJ6wY6ILhfg 149
59 DNA Tools: myOrigins 3.0 Explained, Part 1 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=ACgY3F4-w78 74

 
60 DNA Tools: myOrigins 3.0 Explained, Part 2 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=h7qU36bIFg0 50
61 DNA Tools: myOrigins 3.0 Explained, Part 3 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=SWlGPm8BGyU 36
62 African American Genealogy Research Tips FamilyTreeDNA – Sherman McRae https://www.youtube.com/watch?v=XdbkM58rXIQ 153

 
63 Connecting With My Ancestors Through Y-DNA FamilyTreeDNA – Sherman McRae https://www.youtube.com/watch?v=xbo1XnLkuQU 200
64 Join The Million Mito Project FamilyTreeDNA (Join link) https://www.familysearch.org/rootstech/session/join-the-million-mito-project link
65 View the World’s Largest mtDNA Haplotree FamilyTreeDNA (Link to mtDNA tree) https://www.familytreedna.com/public/mt-dna-haplotree/L n/a
66 View the World’s Largest Y Haplotree FamilyTreeDNA (Link to Y tree) https://www.familytreedna.com/public/y-dna-haplotree/A link
67 A Sneak Peek at FamilyTreeDNA Coming Attractions FamilyTreeDNA (live) https://www.youtube.com/watch?v=K9sKqNScvnE 1270 + live viewers

 
68 DNA Upload: How to Transfer Your Autosomal DNA Data FamilyTreeDNA -Katy Rowe https://www.youtube.com/watch?v=CS-rH_HrGlo 303
69 Family Finder myOrigins: How to Compare Origins With Your DNA Matches FamilyTreeDNA -Katy Rowe https://www.youtube.com/watch?v=7mBmWhM4j9Y 145
70 Join Group Projects at FamilyTreeDNA FamilyTreeDNA link to learning center article) https://www.familysearch.org/rootstech/session/join-group-projects-at-familytreedna link

 
71 Product Demo – Unraveling your genealogy with reconstructed trees using AutoKinship GEDmatch https://www.youtube.com/watch?v=R7_W0FM5U7c 803
72 Towards a Genetic Genealogy Driven Irish Reference Genome Gerard Corcoran https://www.youtube.com/watch?v=6Kx8qeNiVmo 155

 
73 Discovering Biological Origins in Chile With DNA: Simple Triangulation Gonzalo Alexis Luengo Orellana https://www.youtube.com/watch?v=WcVby54Uigc 40
74 Cousin Lynne: An Adoption Story International Association of Jewish Genealogical Societies https://www.youtube.com/watch?v=AptMcV4_B4o 111
75 Using DNA Testing to Uncover Native Ancestry Janine Cloud https://www.youtube.com/watch?v=edzebJXepMA 205
76 1. Forensic Genetic Genealogy Jarrett Ross https://www.youtube.com/watch?v=0euIDZTmx5g 58
77 Reunited and it Feels so Good Jennifer Mendelsohn https://www.youtube.com/watch?v=X-hxjm7grBE 57

 
78 Genealogical Research and DNA Testing: The Perfect Companions Kimberly Brown https://www.youtube.com/watch?v=X82jA3xUVXk 80
79 Finding a Jewish Sperm Donor Kitty Munson Cooper https://www.youtube.com/watch?v=iKRjFfNcpug 164
80 Using DNA in South African Genealogy Linda Farrell https://www.youtube.com/watch?v=HXkbBWmORM0 141
81 Using DNA Group Projects In Your Family History Research Mags Gaulden https://www.youtube.com/watch?v=0tX7QDib4Cw 165
82 2. The Expansion of Genealogy Into Forensics Marybeth Sciaretta https://www.youtube.com/watch?v=HcEO-rMe3Xo 35

 
83 DNA Interest Groups That Keep ’em Coming Back McKell Keeney (live) https://www.youtube.com/watch?v=HFwpmtA_QbE 180 plus live viewers
84 Searching for Close Relatives with Your DNA Results Mckell Keeney (live) https://www.familysearch.org/rootstech/session/searching-for-close-relatives-with-your-dna-results Not yet available
85 Top Ten Reasons To DNA Test For Family History Michelle Leonard https://www.youtube.com/watch?v=1B9hEeu_dic 181
86 Top Tips For Identifying DNA Matches Michelle Leonard https://www.youtube.com/watch?v=-3Oay_btNAI 306
87 Maximising Messages Michelle Patient https://www.youtube.com/watch?v=4TRmn0qzHik 442
88 How to Filter and Sort Your DNA Matches MyHeritage https://www.youtube.com/watch?v=fmIgamFDvc8 88
89 How to Get Started with Your DNA Matches MyHeritage https://www.youtube.com/watch?v=JPOzhTxhU0E 447

 
90 How to Track DNA Kits in MyHeritage` MyHeritage https://www.youtube.com/watch?v=2W0zBbkBJ5w 28

 
91 How to Upload Your DNA Data to MyHeritage MyHeritage https://www.youtube.com/watch?v=nJ4RoZOQafY 82
92 How to Use Genetic Groups MyHeritage https://www.youtube.com/watch?v=PtDAUHN-3-4 62
My Story: Hope MyHeritage https://www.youtube.com/watch?v=qjyggKZEXYA 133
93 MyHeritage Keynote, RootsTech 2022 MyHeritage https://www.familysearch.org/rootstech/session/myheritage-keynote-rootstech-2022 Not available
94 Using Labels to Name Your DNA Match List MyHeritage https://www.youtube.com/watch?v=enJjdw1xlsk 139

 
95 An Introduction to DNA on MyHeritage MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=1I6LHezMkgc 60
96 Using MyHeritage’s Advanced DNA Tools to Shed Light on Your DNA Matches MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=Pez46Xw20b4 110
97 You’ve Got DNA Matches! Now What? MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=gl3UVksA-2E 260
98 My Story: Lizzie and Ayla MyHeritage – Elizbeth Shaltz https://www.youtube.com/watch?v=NQv6C8G39Kw 147
99 My Story: Fernando and Iwen MyHeritage – Fernando Hermansson https://www.youtube.com/watch?v=98-AR0M7fFE 165

 
100 Using the Autocluster and the Chromosome Browser to Explore Your DNA Matches MyHeritage – Gal Zruhen https://www.youtube.com/watch?v=a7aQbfP7lWU 115

 
101 My Story : Kara Ashby Utah Wedding MyHeritage – Kara Ashby https://www.youtube.com/watch?v=Qbr_gg1sDRo 200
102 When Harry Met Dotty – using DNA to break down brick walls Nick David Barratt https://www.youtube.com/watch?v=8SdnLuwWpJs 679
103 How to Add a DNA Match to Airtable Nicole Dyer https://www.youtube.com/watch?v=oKxizWIOKC0 161
104 How to Download DNA Match Lists with DNAGedcom Client Nicole Dyer https://www.youtube.com/watch?v=t9zTWnwl98E 124
105 How to Know if a Matching DNA Segment is Maternal or Paternal Nicole Dyer https://www.youtube.com/watch?v=-zd5iat7pmg 161
106 DNA Basics Part I Centimorgans and Family Relationships Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=SI1yUdnSpHA 372
107 DNA Basics Part II Clustering and Connecting Your DNA Matches Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=ECs4a1hwGcs 333
108 DNA Basics Part III Charting Your DNA Matches to Get Answers Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=qzybjN0JBGY 270
109 2. Using Cluster Auto Painter Patricia Coleman https://www.youtube.com/watch?v=-nfLixwxKN4 691
110 3. Using Online Irish Records Patricia Coleman https://www.youtube.com/watch?v=mZsB0l4z4os 802
111 Exploring Different Types of Clusters Patricia Coleman https://www.youtube.com/watch?v=eEZBFPC8aL4 972

 
112 The Million Mito Project: Growing the Family Tree of Womankind Paul Maier https://www.youtube.com/watch?v=cpctoeKb0Kw 541
113 The Tree of Mankind Age Estimates Paul Maier https://www.youtube.com/watch?v=jjkL8PWAEwk 1638
114 Y-DNA and Mitochondrial DNA Testing Plans Paul Woodbury https://www.youtube.com/watch?v=akymSm0QKaY 168
115 Finding Biological Family Price Genealogy https://www.youtube.com/watch?v=4xh-r3hZ6Hw 137
116 What Y-DNA Testing Can Do for You Richard Hill https://www.youtube.com/watch?v=a094YhIY4HU 191
117 Extending Time Horizons with DNA Rob Spencer (live) https://www.youtube.com/watch?v=wppXD1Zz2sQ 1037 + live viewers
118 DNA for Native American Ancestry by Roberta Estes Roberta Estes https://www.youtube.com/watch?v=EbNyXCFfp4M 212
119 1. Associating Autosomal DNA Segments With Ancestors Roberta Estes (live) https://www.youtube.com/watch?v=_IHSCkNnX48

 

 ~9000: 1019 + 500 live viewers + 7,400+ Facebook
120 1. What Can I Do With Ancestral DNA Segments? Roberta Estes (live) https://www.youtube.com/watch?v=Suv3l4iZYAQ 325 plus live viewers

 
121 Native American DNA – Ancient and Contemporary Maps Roberta Estes (live) https://www.youtube.com/watch?v=dFTl2vXUz_0 212 plus 483 live viewers

 
122 How Can DNA Enhance My Family History Research? Robin Wirthlin https://www.youtube.com/watch?v=f3KKW-U2P6w 102
123 How to Analyze a DNA Match Robin Wirthlin https://www.youtube.com/watch?v=LTL8NbpROwM 367
124 1. Jewish Ethnicity & DNA: History, Migration, Genetics Schelly Talalay Dardashti https://www.youtube.com/watch?v=AIJyphGEZTA 82

 
125 2. Jewish Ethnicity & DNA: History, Migration, Genetics Schelly Talalay Dardashti https://www.youtube.com/watch?v=VM3MCYM0hkI 72
126 Ask us about DNA Talking Family History (live) https://www.youtube.com/watch?v=kv_RfR6OPpU 96 plus live viewers
127 1. An Introduction to Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=WNhErW5UVKU

 

 183
128 2. An Introduction to Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=CRpQ8EVOShI 110

 
129 Common Problems When Doing Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=hzFxtBS5a8Y 68
130 Cross Visual Phasing to Go Back Another Generation Tanner Blair Tolman https://www.youtube.com/watch?v=MrrMqhfiwbs 64
131 DNA Basics Tanner Blair Tolman https://www.youtube.com/watch?v=OCMUz-kXNZc 155
132 DNA Painter and Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=2-eh1L4wOmQ 155
133 DNA Painter Part 2: Chromosome Mapping Tanner Blair Tolman https://www.youtube.com/watch?v=zgOJDRG7hJc 172
134 DNA Painter Part 3: The Inferred Segment Generator Tanner Blair Tolman https://www.youtube.com/watch?v=96ai8nM4lzo

 

 100
135 DNA Painter Part 4: The Distinct Segment Generator Tanner Blair Tolman https://www.youtube.com/watch?v=Pu-WIEQ_8vc 83
136 DNA Painter Part 5: Ancestral Trees Tanner Blair Tolman https://www.youtube.com/watch?v=dkYDeFLduKA 73
137 Understanding Your DNA Ethnicity Results Tanner Blair Tolman https://www.youtube.com/watch?v=4tAd8jK6Bgw 518
138 What’s New at GEDmatch Tim Janzen https://www.youtube.com/watch?v=AjA59BG_cF4

 

 515
139 What Does it Mean to Have Neanderthal Ancestry? Ugo Perego https://www.youtube.com/watch?v=DshCKDW07so 190
140 Big Y-700 Your DNA Guide https://www.youtube.com/watch?v=rIFC69qswiA 143
141 Next Steps with Your DNA Your DNA Guide – Diahan Southard (live) https://www.familysearch.org/rootstech/session/next-steps-with-your-dna Not yet available

Additions:

142  Adventures of an Amateur Genetic Genealogist – Geoff Nelson https://www.familysearch.org/rootstech/session/adventures-of-an-amateur-genetic-genealogist     291 views

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Identify Your Ancestors – Follow Nested Ancestral Segments

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15

I don’t think that we actively think about our DNA segments as nested ancestors, like Russian Matryoshka dolls, but they are.

That’s exactly why segment information is critical for genealogists. Every segment, and every portion of a segment, has an incredibly important history. In fact, you could say that the further back in time we can track a segment, the more important it becomes.

Let’s see how to unveil nested segments. I’ll use my chromosome 20 as an example because it’s a smaller chromosome. But first, let’s start with my pedigree chart.

Pedigree

Click images to enlarge.

Before we talk about nested segments that originated with specific ancestors, it’s important to take a look at the closest portion of my maternal pedigree chart. My DNA segments came from and through these people. I’ll be working with the first 5 generations, beginning with my mother as generation #1.

Generation 1 – Parents

In the first generation, we receive a copy of each chromosome from each parent. I have a copy of chromosome 20 from my mother and a copy from my father.

At FamilyTreeDNA, you can see that I match my mother on the entire tested region of each chromosome.

Therefore, the entire length of each of my chromosomes is assigned to both mother and father because I received a copy from each parent. I’m fortunate that my mother’s DNA was able to be tested before she passed away.

We see that each copy of chromosome 20 is a total of 110.20 cM long with 17,695 SNPs.

Of course, my mother inherited the DNA on her chromosome 20 from multiple ancestors whose DNA combined in her parents, a portion of which was inherited by my mother. Mom received one chromosome from each of her parents.

I inherited only one copy of each chromosome (In this case, chromosome 20) from Mom, so the DNA of her two parents was divided and recombined so that I inherited a portion of my maternal chromosome 20 from both of my maternal grandparents.

Identifying Maternal and Paternal Matches

Associating matches with your maternal or paternal side is easy at FamilyTreeDNA because their Family Finder matching does it automatically for you if you upload (or create) a tree and link matches that you can identify to their proper place in your tree.

FamilyTreeDNA then uses that matching segment information from known, identified relatives in your tree to place people who match you both on at least one significant-sized segment in the correct maternal, paternal, (or both) buckets. That’s triangulation, and it happens automatically. All you have to do is click on the Maternal tab to view your triangulated maternal matches. As you can see, I have 1432 matches identified as maternal. 

Some other DNA testing companies and third-party tools provide segment information and various types of triangulation information, but they aren’t automated for your entire match list like Family Finder matching at FamilyTreeDNA.

You can read about triangulation in action at MyHeritage, here, 23andMe, here, GEDmatch, here, and DNAPainter, which we’ll use, here. Genetic Affairs AutoKinship tool incorporates triangulation, as does their AutoSegment Triangulation Cluster Tool at GEDmatch. I’ve compiled a reference resource for triangulation, here.

Every DNA testing vendor has people in their database that haven’t tested anyplace else. Your best strategy for finding nested segments and identifying matches to specific ancestors is to test at or transfer your DNA file to every vendor plus GEDmatch where people who test at Ancestry sometimes upload for matching. Ancestry does not provide segment information or a chromosome browser so you’ll sometimes find Ancestry testers have uploaded to GEDmatch, FamilyTreeDNA  or MyHeritage where segment information is readily available. I’ve created step-by-step download/upload instructions for all vendors, here.

Generation 2 – Grandparents

In the second generation, meaning that of my grandparents, I inherited portions of my maternal and paternal grandmother’s and grandfather’s chromosomes.

My maternal and paternal chromosomes can be divided into two pieces or groups each, one for each grandparent.

Using DNAPainter, we can see my father’s chromosome 20 on top and my mother’s on the bottom. I have previously identified segments assigned to specific ancestors which are represented by different colors on these chromosomes. You can read more about how to use DNAPainter, here.

We can divide the DNA inherited from each parent into the DNA inherited from each grandparent based on the trees of people we match. If we test cousins from each side, assigning segments maternally or paternally becomes much, much easier. That’s exactly why I’ve tested several.

For the rest of this article, I’m focusing only on my mother’s side because the concepts and methods are the same regardless of whether you’re working on your maternal side or your paternal side.

Using DNAPainter, I expanded my mother’s chromosome 20 in order to see all of the people I’ve painted on my mother’s side.

DNAPainter allows us to paint matching segments from multiple testing vendors and assign them to specific ancestors as we identify common ancestors with our matches.

Based on these matches, I’ve divided these maternal matches into two categories:

  • Maternal grandmother, meaning my mother’s mother, bracketed in red boxes
  • Maternal grandfather, meaning my mother’s father, bracketed in black boxes.

The text and arrows in these graphics refer to the colors of the brackets/boxes, and NOT the colors of the segments beside people’s names. For example, if you look at the large black box at far right, you’ll see several people, with their matching segments identified by multiple colored bars. The different colored segments (bars) mean I’ve associated the match with different ancestors in multiple or various levels of generations.

Generation 3 – Great-grandparents

Within those maternal and paternal grandparent segments, more nested information is available.

The black Ferverda grandfather segments are further divided into black, from Hiram Ferverda, and gold from his wife Eva Miller. The same concept applies to the red grandmother segments which are now divided into red representing Nora Kirsch and purple representing Curtis Lore, her husband.

While I have only been able to assign the first four segments (at the top) to one person/ancestor, there’s an entire group of matches who share the grouping of segments at right, in gold, descended through Eva Miller. The Miller line is Brethren and Mennonite with lots of testers, so this is a common pattern in my DNA matches.

Eva Miller, the gold ancestor, has two parents, Margaret Elizabeth Lentz and John David Miller, so her segments would come from those two sides.

Generation 4 and 5 – Fuschia Segment

I was able to track the segment shown in fuschia indicated by the blue arrow to Jacob Lentz and his wife Fredericka Ruhle, German immigrant ancestors. Other people in this same match (triangulation) group descend from Margaret Elizabeth Lentz and John David Miller – but that fuschia match is the one that shows us where that segment originated. This allows us to assign that entire gold/blue bracketed set of segments to a specific ancestor or ancestral couple because they triangulate, meaning they all match me and each other.

Therefore, all of the segments that match with the fuschia segment also track back to Jacob Lentz and Fredericka Ruhle, or to their ancestors. We would need people who descend from Jacob’s parents and/or Fredericka’s parents to determine the origins of that segment.

In other words, we know all of these people share a common source of that segment, even if we don’t yet know exactly who that common ancestor was or when they lived. That’s what the process of tracking back discovers.

To be very clear, I received that segment through Jacob and Fredericka, but some of those matches who I have not been able to associate with either Jacob or Fredericka may descend from either Jacob or Fredericka’s ancestors, not Jacob and Fredericka themselves. Connecting the dots between Jacob/Fredericka and their ancestors may be enlightening as to the even older source of that segment.

Let’s take a look at nested segments on my pedigree chart.

Nested Pedigree

Click to enlarge.

You can see the progression of nesting on my pedigree chart, using the same colors for the brackets/boxes. The black Ferverda box at the grandparent level encompasses the entire paternal side of my mother’s ancestry, and the red includes her mother’s entire side. This is identical to the DNAPainter graphic, just expressed on my pedigree chart instead of my chromosome 20.

Then the black gets broken into smaller nested segments of black, gold and fuschia, while the red gets broken into red and purple.

If I had more matches that could be assigned to ancestors, I would have even more nested levels. Of course, if I was using all of my chromosomes, not just 20, I would be able to go back further as well.

You can see that as we move further back in time, the bracketed areas assigned to each color become smaller and smaller, as do the actual segments as viewed on my DNAPainter chromosomes.

Segments Get Progressively Smaller

You can see in the pedigree chart and segment painting above that the segments we inherit from specific ancestors divide over time. As we move further and further back in our tree, the segments inherited from any specific ancestor get smaller and smaller too.

Dr. Paul Maier in the MyOrigins 3.0 White Paper provides this informative graphic that shows the reduction in segments and the number of ancestors whose DNA we carry reaching back in time.

I refer to this as a porcupine chart.

Eventually, we inherit no segments from red ancestors, and the pieces of DNA that we inherit from the distant blue ancestors become so small and fragmented that they cannot be positively identified as coming from a specific ancestor when compared to and matched with other people. That’s why vendors don’t show small segment matches, although different vendors utilize different segment thresholds.

The debate about how small is too small continues, but the answer is not simply segment size alone. There is no one-size-fits-all answer.

As segments become smaller, the probability, or chances that we match another person by chance (IBC) increases. Proof that someone shares a specific ancestor, especially when dealing with increasingly smaller segments is a function of multiple factors, such as tree completeness for both people, shared matches, parental match confirmation, and more. I wrote about What Constitutes Proof, here.

In the Family Finder Matching White Paper, Dr. Maier provides this chart reflecting IBD (Identical By Descent) and IBC (Identical By Chance) segments and the associated false positivity rate. That means how likely you are to match someone on a segment of that size by chance and NOT because you both share the DNA from a common ancestor.

I wrote Concepts: Identical by Descent, State, Population and Chance to help you better understand how this works.

In the chart below, I’ve combined the generations, relationships, # of ancestors, assuming no duplicates, birth year range based on an approximate 30-year generation, percent of DNA assuming exactly half of each ancestor’s DNA descends in each generation (which we know isn’t exactly accurate), and the average amount of total inherited cMs using that same assumption.

Note that beginning with the 7th generation, on average, we can expect to inherit less than 1% of the DNA of an ancestor, or approximately 55 total cM which may be inherited in multiple segments.

The amount of actual cMs inherited in each generation can vary widely and explains why, beginning with third cousins, some people won’t share DNA from a common ancestor above the various vendor matching thresholds. Yet, other cousins several generations removed will match. Inheritance is random.

Parallel Inheritance

In order to match someone else descended from that 11th generation ancestor, BOTH you AND your match will need to have inherited the exact SAME DNA segment, across 11 generations EACH in order to match. This means that 11 transmission events for each person will need to have taken place in parallel with that identical segment being passed from parent to child in each line. For 22 rolls of the genetic dice in a row, the same segment gets selected to be passed on.

You can see why we all need to work to prove that distant matches are valid.

The further back in time we work, the more factors we must take into consideration, and the more confirming proof is needed that a match with another individual is a result of a shared ancestor.

Having said that, shared distant matches ARE the key to breaking through brick-wall ancestors. We just need to be sure we are chasing the real deal and not a red herring.

Exciting Possibilities

The most exciting possibility is that some segments are actually passed intact for several generations, meaning those segments don’t divide into segments too small for matching.

For example, the 22 cM fuschia segment that tracks through generations 4 and 5 to Jacob Lentz and Fredericka Ruhle has been passed either intact or nearly intact to all of those people who stack up and match each other and me on that segment. 22 cM is definitely NOT a small segment and we know that it descended from either Jacob or Fredericka, or perhaps combined segments from each. In any case, if someone from the Lentz line in Germany tested and matched me on that segment (and by inference, the rest of these people too), we would know that segment descended to me from Jacob Lentz – or at least the part we match on if we don’t match on the entire segment.

This is exactly what nested segments are…breadcrumbs to ancestors.

Part of that 22cM segment could be descended from Jacob and part from Fredericka. Then of Jacob’s portion, for example, pieces could descend from both his mother and father.

This is why we track individual segments back in time to discern their origin.

The Promise of the Future

The promise of the future is when a group of other people triangulate on a reasonably sized segment AND know where it came from. When we match that triangulation group, their identified segment may well help break down our brick walls because we match all of them on that same segment.

It is exactly this technique that has helped me identify a Womack segment on my paternal line. I still haven’t identified our common ancestor, but I have confirmed that the Womacks and my Moore/Rice family interacted as neighbors 8 generations ago and likely settled together in Amelia county, migrating from eastern Virginia. In time, perhaps I’ll be able to identify the common Womack ancestor and the link into either my Moore or Rice lines.

I’m hoping for a similar breakthrough on my mother’s side for Philip Jacob Miller’s wife, Magdalena, 7 generations back in my tree. We know Magdalena was Brethren and where they lived when they took up housekeeping. We don’t know who her parents were. However, there are thousands of Miller descendants, so it’s possible that eventually, we will be able to break down that brick wall by using nested segments – ours and people who descend from Magdalena’s siblings, aunts, and uncles.

Whoever those people were, at least some of their descendants will likely match me and/or my cousins on at least one nested Miller segment that will be the same segment identified to their ancestors.

Genealogy is a team sport and solving puzzles using nested segments requires that someone out there is working on identifying triangulated segments that track to their common ancestors – which will be my ancestors too. I have my fingers crossed that someone is working on that triangulation group and I find them or they find me. Of course, I’m working to triangulate and identify my segments to specific ancestors – hoping for a meeting in the middle – that much-desired bridge to the past.

By the time you’ve run out of other records, nested segments are your last chance to identify those elusive ancestors. 

Do you have genealogical brick walls that nested segments could solve?

__________________________________________________________

Follow DNAexplain on Facebook, here or follow me on Twitter, here. You can also subscribe to receive emails when I publish articles by clicking the “Follow” button at www.DNAexplain.com.

You’re always welcome to forward articles or links to friends.

You Can Help Out and It’s Free

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 Uploads

Genealogy Products and Services

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2021 Favorite Articles

Posted on by
8

It’s that time of the year again when we welcome the next year.

2021 was markedly different than anything that came before. (Is that ever an understatement!)

Maybe you had more time for genealogy and spent time researching!

So, what did we read in 2021? Which of my blog articles were the most popular?

In reverse order, beginning with number 10, we have:

This timeless article published in 2015 explains how to calculate the amount of any specific heritage you carry based on your ancestors.

Just something fun that’s like your regular pedigree chart, except color coded locations instead of ancestors. Here’s mine

The Autosegment Triangulation Cluster Tool is a brand new tool introduced in October 2021. Created by Genetic Affairs for GEDmatch, this tool combines autoclusters and triangulation.

Many people don’t realize that we actually don’t inherit exactly 25% of our DNA from each grandparent, nor why.

This enlightening article co-authored with statistician Philip Gammon explains how this works, and why it affects all of your matches.

Who doesn’t love learning about ancient DNA and the messages it conveys. Does your Y or mitochondrial DNA match any of these burials? Take a look. You might be surprised.

How can you tell if you are full or half siblings with another person? You might think this is a really straightforward question with an easy answer, but it isn’t. And trust me, if you EVER find yourself in a position of needing to know, you really need to know urgently.

Using simple match, it’s easy to figure how much of your ancestor’s DNA you “should” have, but that’s now how inheritance actually works. This article explains why and shows different inheritance scenarios.

That 28 day timer has expired, but the article can still be useful in terms of educating yourself. This should also be read in conjunction with Ancestry Retreats, by Judy Russell.

If I had a dollar for every time I’ve heard someone say that their ethnicity percentages were “wrong,” I’d be a rich woman, living in a villa in sun-drenched Tuscany😊

This extremely popular article has either been first or second every year since it was published. Ethnicity is both exciting and perplexing.

As genealogists, the first thing we need to do is to calculate what, according to our genealogy, we would expect those percentages to be. Of course, we also need to factor in the fact that we don’t inherit exactly the same amount of DNA from each grandparent. I explain how I calculated my “expected” percentages of ethnicity based on my known tree. That’s the best place to start.

Please note that I am no longer updating the vendor comparison charts in the article. Some vendors no longer release updates to the entire database at the same time, and some “tweak” results periodically without making an announcement. You’ll need to compare your own results at the different vendors at the same point in time to avoid comparing apples and oranges.

The #1 Article for 2021 is…

  1. Proving Native American Ancestry Using DNA

This article has either been first (7 times) or second (twice) for 9 years running. Now you know why I chose this topic for my new book, DNA for Native American Genealogy.

If you’re searching for your Native American ancestry, I’ve provided step-by-step instructions, both with and without some percentage of Native showing in your autosomal DNA percentages.

Make 2022 a Great Year!

Here’s wishing you the best in 2022. I hope your brick walls cave. What are you doing to help that along? Do you have a strategy in mind?

__________________________________________________________

Follow DNAexplain on Facebook, here or follow me on Twitter, here. You can also subscribe to receive emails when I publish articles by clicking the “Follow” button at www.DNAexplain.com.

You’re always welcome to forward articles or links to friends.

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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.

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DNA for Native American Genealogy – Hot Off the Press!

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Drum roll please…my new book, DNA for Native American Genealogy, was just released today, published by Genealogical.com.

I’m so excited! I expected publication around the holidays. What a pleasant surprise.

This 190-page book has been a labor of love, almost a year in the making. There’s a lot.

  • Vendor Tools – The book incorporates information about how to make the best use of the autosomal DNA tools offered by all 4 of the major testing vendors; FamilyTreeDNA, MyHeritage, Ancestry, and 23andMe.
  • Chromosome Painting – I’ve detailed how to use DNAPainter to identify which ancestor(s) your Native heritage descends from by painting your population/ethnicity segments provided by FamilyTreeDNA and 23andMe.
  • Y and Mitochondrial DNA – I’ve described how and when to utilize the important Y and mitochondrial DNA tests, for you and other family members.
  • Maps – Everyone wants to know about ancient DNA. I’ve included ancient DNA information complete with maps of ancient DNA sites by major Native haplogroups, gathered from many academic papers, as well as mapped contemporary DNA locations.
  • Haplogroups – Locations in the Americas, by haplogroup, where individual haplogroups and subgroups are found. Some haplogroups are regional in nature. If you happen to have one of these haplogroups, that’s a BIG HINT about where your ancestor lived.
  • Tribes – Want to know, by tribe, which haplogroups have been identified? Got you covered there too.
  • Checklist – I’ve provided a checklist type of roadmap for you to follow, along with an extensive glossary.
  • Questions – I’ve answered lots of frequently asked questions. For example – what about joining a tribe? I’ve explained how tribes work in the US and Canada, complete with links for relevant forms and further information.

But wait, there’s more…

New Revelations!!!

There is scientific evidence suggesting that two haplogroups not previously identified as Native are actually found in very low frequencies in the Native population. Not only do I describe these haplogroups, but I provide their locations on a map.

I hope other people will test and come forward with similar results in these same haplogroups to further solidify this finding.

It’s important to understand the criteria required for including these haplogroups as (potentially) Native. In general, they:

  • Must be found multiple times outside of a family group
  • Must be unexplained by any other scenario
  • Must be well-documented both genetically as well as using traditional genealogical records
  • Must be otherwise absent in the surrounding populations

This part of the research for the book was absolutely fascinating to me.

Description

Here’s the book description at Genealogical.com:

DNA for Native American Genealogy is the first book to offer detailed information and advice specifically aimed at family historians interested in fleshing out their Native American family tree through DNA testing.

Figuring out how to incorporate DNA testing into your Native American genealogy research can be difficult and daunting. What types of DNA tests are available, and which vendors offer them? What other tools are available? How is Native American DNA determined or recognized in your DNA? What information about your Native American ancestors can DNA testing uncover? This book addresses those questions and much more.

Included are step-by-step instructions, with illustrations, on how to use DNA testing at the four major DNA testing companies to further your genealogy and confirm or identify your Native American ancestors. Among the many other topics covered are the following:

    • Tribes in the United States and First Nations in Canada
    • Ethnicity
    • Chromosome painting
    • Population Genetics and how ethnicity is assigned
    • Genetic groups and communities
    • Y DNA paternal direct line male testing for you and your family members
    • Mitochondrial DNA maternal direct line testing for you and your family members
    • Autosomal DNA matching and ethnicity comparisons
    • Creating a DNA pedigree chart
    • Native American haplogroups, by region and tribe
    • Ancient and contemporary Native American DNA

Special features include numerous charts and maps; a roadmap and checklist giving you clear instructions on how to proceed; and a glossary to help you decipher the technical language associated with DNA testing.

Purchase the Book and Participate

I’ve included answers to questions that I’ve received repeatedly for many years about Native American heritage and DNA. Why Native DNA might show in your DNA, why it might not – along with alternate ways to seek that information.

You can order DNA for Native American Genealogy, here.

For customers in Canada and outside the US, you can use the Amazon link, here, to reduce the high shipping/customs costs.

I hope you’ll use the information in the book to determine the appropriate tests for your situation and fully utilize the tools available to genealogists today to either confirm those family rumors, put them to rest – or maybe discover a previously unknown Native ancestor.

Please feel free to share this article with anyone who might be interested.

_____________________________________________________________

Disclosure

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 Uploads

Genealogy Products and Services

My Book

Genealogy Books

Genealogy Research

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

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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.

Endogamy

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?

Imputation

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?

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.

Whew!!!

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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Thank you so much.

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How to Download Your DNA Matching Segment Data and Why You Should

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There are two or three types of data that testers may be able to download from DNA testing sites. Genealogy customers need to periodically download as much as possible.

  1. Raw data files needed for transferring DNA files from the company where you tested to other testing or analysis/comparison sites such as FamilyTreeDNA, MyHeritage, and GEDmatch for matching and other tools.
  2. Matching segment files which detail your matches, segment by segment with people whom you match.
  3. Match information files that provide you with additional information about your matches. What’s included varies by vendor.

This type of information is not uniformly available from all vendors, but is available as follows:

Vendor Raw Data File Matching Segment File Match Information File
FamilyTreeDNA Yes Yes Yes
MyHeritage Yes Yes Yes
23andMe Yes Yes Yes
Ancestry Yes No No
GedMatch Not a testing company, so no Yes Yes

I have provided step-by-step information about how to download your raw DNA data files and upload them to other vendors in a series of articles that you can find here.

Some of the answers in the table above need caveats because each vendor is different. Let’s take a look.

Matching Segment Files

In this article, I’ll provide information about how to download your matching segment and match information file(s).

Unfortunately, Ancestry does not provide any segment data at all, nor do they provide a way to download your match information. Third-party tools that did this for you have been banned by Ancestry, under threat of legal action, so this information is no longer available to Ancestry customers.

You can’t obtain this information from Ancestry, but you can transfer your DNA file to other vendors such as FamilyTreeDNA, MyHeritage and the third-party site, GEDmatch where you’ll receive additional matches. Some Ancestry matches will have transferred elsewhere as well, and you can take advantage of your matching segment information.

Why Do I Want a Matching Segment File?

The matching segment file provides you with information about exactly how and where you match each person.

Here’s an example that includes the match name, chromosome, start and end location of the match along with the total number of CentiMorgans (cM) and total SNPs in the matching segment. Your matching segment file consists of hundreds/thousands of rows of this information.

Determining who matches you on the same segment is important because it facilitates the identification of common ancestors. Segment matching is also the first step in triangulation which allows you to confirm descent from common ancestors with your matches.

I wrote about triangulation at each vendor in the following articles:

Matching and Triangulation help you sort out legitimate matches, and which ancestors that DNA segment comes from.

Sorting For Legitimate Matches

On each segment location of your DNA, you will match:

  • People from your Mom’s side
  • People from your Dad’s side
  • People that are identical by chance (IBC) where they match you because part of the DNA from your Mom’s side and part from your Dad’s side just happens to look like their DNA (or vice versa.)

You can see how matching works in this example of 10 DNA locations. You inherited half of your Mom’s DNA and half of your Dad’s.

  • Legitimate maternal matches to you on this segment will have all As in this location.
  • Legitimate paternal matches to you will have all Cs in this location.
  • Identical by chance matches will match you, because they have the same DNA as both of your parents that you carry – interspersed. They will not match either of your parents individually.

IBC matches DO technically match you, but accidentally. In other words, they are identical by chance (IBC) because they just happen to match the DNA of both of your parents intermixed. Conversely, you can match the DNA of their parents intermixed as well. Regardless of why, they are not a legitimate maternal or paternal match to you.

For example, you can see that the identical by chance (IBC) match to you, above, won’t match the legitimate maternal or legitimate paternal matches.

When comparing your matches on any segment, you’ll wind up with a group of people who match you and each other on your maternal side, a group on your paternal side, and “everyone else” who is IBC.

I wrote about IBD, identical by descent DNA and IBC, identical by chance DNA and how that works, here.

A downloadable segment match file allows you to sort all of your matches by chromosome and segment. That’s the first step in determining if your matches match each other – which is how to determine if people are legitimate matches or IBC.

Additionally, these files allow you to utilize features at DNAPainter along with the tools at DNAGedcom and Genetic Affairs.

Match Information File

There’s a second file you’ll want to download as well except at 23andMe who includes all of the information in one file. You’ll want to download these files from each vendor at the same time so they are coordinated and include the same matches from the same time.

Downloading the second file, your match information, provides additional information which will be helpful for your genealogy. The information in this file varies by vendor, but includes items such as, but not limited to:

  • Tree link
  • Haplogroup
  • Match date
  • Predicted Relationship Range
  • Actual Relationship
  • Total shared cM
  • Longest segment cM
  • Maternal or paternal bucket (FamilyTreeDNA)
  • Notes
  • Email
  • Family Surnames
  • Location
  • Percent of shared DNA

You never know when vendors are going to change something that will affect your matches, like 23andMe did last fall, so it’s a good idea to download periodically.

Downloading your segment match and match information files are free, so let’s do this.

Downloading Your Segment Match & Information Files

FamilyTreeDNA

Sign on to your account.

click images to enlarge

Under your Family Finder Autosomal DNA test results, click on Chromosome Browser.

On the chromosome browser page, at the top right, click on Download All Segments.

Caveat – if you access the chromosome browser through the Family Finder match page, shown below, you will receive the segment matches ONLY for the people you have selected.

After selecting specific matches, as shown above, the option on the chromosome browser page will only say “Download Segments.” It does NOT say “Download All Segments.”

Clicking on this link only downloads the segments that you match with those people, so always be sure to access “Download ALL Segments” directly through the chromosome browser selection on your Autosomal DNA Family Finder menu without going to your match page and selecting specific matches.

The segment download file includes only the segments, but not additional information, such as which side, maternal or paternal, those matches are bucketed to, surnames and so forth. You need to download a second file.

To download additional information about your matches, scroll to the very bottom of your Family Finder match page and click on either Download Matches or Download Filtered matches. If you’ve used a filter such as maternal or paternal, you’ll receive only those matches, so be sure no filters are in use to download all of your matches’ information.

Your reports will be downloaded to your computer, so save them someplace where you can find them.

MyHeritage

Sign in to your account and click on the DNA tab, then DNA Matches.

At the far right-hand side, you’ll see three little dots. Click on the dots and you’ll see the options to export both the entire DNA Matches list and the shared DNA segment info for all DNA Matches.

You’ll want to download both. The first file Is the DNA matches list.

To download your segment matches, select the second option, “Export shared DNA segment info…”

Your files will be emailed to you.

23andMe

At 23andMe, sign on to your account and click on “DNA Relatives” under the Ancestry tab.

You’ll see your list of matches. Scroll to the very bottom where you’ll see the link to “Download aggregate data.”

23andMe combines your segment and match information in one file.

Remember that at 23andMe, your matches are limited to 2000 (unless you’re a V5 subscriber), minus the number of people who have not opted in to Relative Sharing. Additionally, there will be a number of people in the download file whose names appear, but who don’t have any segment data. Those people opted-in to Relative Sharing, but not to share segment information.

For example, my download file has 2827 rows. Of those, 1769 are unique individuals, meaning that I have matches with multiple segments for 1058 people. This means that of my 2000 allowed matches, 231 (or more) did not opt-in for Relative Sharing. The “or more” means that 23andMe does not roll matches off the list if you have communicated with the person, so some people may actually have more than 2000 matches. It’s impossible to know how 23andMe approaches calculations in this case.

Of those 1769 unique individuals on my match list, 257, or 15% did not share segment information. I’d sure like for those to be automatically rolled off and replaced with the next 257 who do share. 1512 or roughly three-quarters, 75%, of my 2000 allowed matches are useful for genealogy.

Initially, when 23andMe made their changes last fall, they were reportedly limiting the download file number to 1000, but they have reversed that policy on the V3 and V4 chips. I downloaded files from both chip versions to confirm that’s true.

I don’t have the V5 chip subscription level, nor am I going to retest to do that, so I don’t know if V5 subscribers receive all 5000 of the allowed matches in their download file.

This is the perfect example of why it’s a good idea to download your match files periodically. 23andMe is the only testing vendor that restricts your matches and when they roll off your list, they are irretrievable.

Aside from that, safe is better than sorry. You never know when something will change at a vendor and you’ll wish you had downloaded your match files earlier.

GedMatch

GedMatch, a third-party vendor, provides lots of tools but isn’t intuitive and provides almost no tutorial or information about how to navigate or use their site. There are some YouTube videos and Kitty Cooper has written several how-to articles. GEDmatch has promised a facelift soon.

GEDmatch provides many tools for free, along with a Tier1 level which provides advanced features by subscription.

At GEDmatch, you can see up to 2000 matches for free, but you must be a Tier 1 subscription member to download your matches – and the download is restricted to your top 1000 matches.

There are two Tier 1 one-to-many comparison options that are very similar. For either, you’ll enter your kit number and make your selection. Given that you’re restricted to 1000 in the download, there is no reason to search for more than 1000 kits.

click to enlarge

Then, click on Visualization options

You will then see the list of visualization options which includes “List/CSV.”

Clicking on “List/CSV” provides you with options.

click to enlarge

You’ll want to select the Matched Segment List, and you can either select “Prevent Hard Breaks,” or not. Allowing hard breaks means that small non-matching regions between two matching segments is not ignored, and the two segments are reported as two separate segments – if they are large enough to be reported.

If you prevent hard breaks, non-matching regions of less than 500,000 thousand base positions are ignored, creating one larger blended segment. It’s my preference to allow hard breaks because I’ve seen too many instances of erroneously “blended” segments.

When your matching segment file is complete, you will be prompted to download to your computer.

Thanks to Genetic Affairs, I discovered an alternate way to obtain more than 1000 downloaded matches from GEDmatch.

GEDmatch Alternative Methodology

Genetic Affairs suggests using the DNA Segment Search with a minimum of 5000 kits, and to enable the option to “Prevent Hard Breaks.”

Do not close the session while GedMatch is processing or you’ll need to restart your query.

When finished click “Here” to download the file to your system.

Now you’re ready for part 2.

Next, you’ll want to select the Triangulation feature.

These functions take time, so you’ll be watching as the counter increases. Or maybe go eat dinner or research some genealogy.

I can hear the “Jeopardy countdown music…

When finished, click on “Here” to download this second file.

Whew! Now you should have your segment and match information files from each company that supports this information and provides downloads.

Saving Files

I generally save my files by vendor and date. However, if you’re going to use the files for a special project – you may want to make a copy elsewhere. For example, I’m going to use these files for Genetic Affairs’ AutoSegment feature, so I’ve downloaded fresh files from each vendor on the same date and made a separate copy, stored in my Genetic Affairs folder. I’ll let you know how that goes😊

Bottom Line

  • Test at vendors that don’t accept transfers. Ancestry and 23andMe
  • Test at or transfer to the rest. FamilyTreeDNA, MyHeritage and GEDmatch
  • Unlock or subscribe to the advanced tools that include chromosome browsers, ethnicity, and more, depending on the vendor. FamilyTreeDNA, MyHeritage, GEDmatch
  • Upload or create trees at each vendor (except 23andMe who doesn’t support trees.)
  • Download as much information as you can from each vendor.
  • Work your matches through shared (in common with) matches, trees, segments, and clusters!

Have fun!!!

_____________________________________________________________

Disclosure

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

Genealogy Products and Services

Books

Genealogy Research

Concepts: Inheritance

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Inheritance.

What is it?

How does it work?

I’m not talking about possessions – but about the DNA that you receive from your parents, and their parents.

The reason that genetic genealogy works is because of inheritance. You inherit DNA from your parents in a known and predictable fashion.

Fortunately, we have more than one kind of DNA to use for genealogy.

Types of DNA

Females have 3 types of DNA and males have 4. These different types of DNA are inherited in various ways and serve different genealogical purposes.

Males Females
Y DNA Yes No
Mitochondrial DNA Yes Yes
Autosomal DNA Yes Yes
X Chromosome Yes, their mother’s only Yes, from both parents

Different Inheritance Paths

Different types of DNA are inherited from different ancestors, down different ancestral paths.

Inheritance Paths

The inheritance path for Y DNA is father to son and is inherited by the brother, in this example, from his direct male ancestors shown by the blue arrow. The sister does not have a Y chromosome.

The inheritance path for the red mitochondrial DNA for both the brother and sister is from the direct matrilineal ancestors, only, shown by the red arrow.

Autosomal DNA is inherited from all ancestral lines on both the father’s and mother’s side of your tree, as illustrated by the broken green arrow.

The X chromosome has a slightly different inheritance path, depending on whether you are a male or female.

Let’s take a look at each type of inheritance, how it works, along with when and where it’s useful for genealogy.

Autosomal DNA

Autosomal DNA testing is the most common. It’s the DNA that you inherit from both of your parents through all ancestral lines back in time several generations. Autosomal DNA results in matches at the major testing companies such as FamilyTreeDNA, MyHeritage, Ancestry, and 23andMe where testers view trees or other hints, hoping to determine a common ancestor.

How does autosomal DNA work?

22 autosomes

Every person has two each of 22 chromosomes, shown above, meaning one copy is contributed by your mother and one copy by your father. Paired together, they form the two-sided shape we are familiar with.

For each pair of chromosomes, you receive one from your father, shown with a blue arrow under chromosome 1, and one from your mother, shown in red. In you, these are randomly combined, so you can’t readily tell which piece comes from which parent. Therein lies the challenge for genealogy.

This inheritance pattern is the same for all chromosomes, except for the 23rd pair of chromosomes, at bottom right, which determined the sex of the child.

The 23rd chromosome pair is inherited differently for males and females. One copy is the Y chromosome, shown in blue, and one copy is the X, shown in red. If you receive a Y chromosome from your father, you’re a male. If you receive an X from your father, you’re a female.

Autosomal Inheritance

First, let’s talk about how chromosomes 1-22 are inherited, omitting chromosome 23, beginning with grandparents.

Inheritance son daughter

Every person inherits precisely half of each of their parents’ autosomal DNA. For example, you will receive one copy of your mother’s chromosome 1. Your mother’s chromosome 1 is a combination of her mother’s and father’s chromosome 1. Therefore, you’ll receive ABOUT 25% of each of your grandparents’ chromosome 1.

Inheritance son daughter difference

In reality, you will probably receive a different amount of your grandparent’s DNA, not exactly 25%, because your mother or father will probably contribute slightly more (or less) of the DNA of one of their parents than the other to their offspring.

Which pieces of DNA you inherit from your parents is random, and we don’t know how the human body selects which portions are and are not inherited, other than we know that large pieces are inherited together.

Therefore, the son and daughter won’t inherit the exact same segments of the grandparents’ DNA. They will likely share some of the same segments, but not all the same segments.

Inheritance maternal autosomalYou’ll notice that each parent carries more of each color DNA than they pass on to their own children, so different children receive different pieces of their parents’ DNA, and varying percentages of their grandparents’ DNA.

I wrote about a 4 Generation Inheritance Study, here.

Perspective

Keep in mind that you will only inherit half of the DNA that each of your parents carries.

Looking at a chromosome browser, you match your parents on all of YOUR chromosomes.

Inheritance parental autosomal

For example, this is me compared to my father. I match my father on either his mother’s side, or his father’s side, on every single location on MY chromosomes. But I don’t match ALL of my father’s DNA, because I only received half of what he has.

From your parents’ perspective, you only have half of their DNA.

Let’s look at an illustration.

Inheritance mom dad

Here is an example of one of your father’s pairs of chromosomes 1-22. It doesn’t matter which chromosome, the concepts are the same.

He inherited the blue chromosome from his father and the pink chromosome from his mother.

Your father contributed half of his DNA to you, but that half is comprised of part of his father’s chromosome, and part of his mother’s chromosome, randomly selected in chunks referred to as segments.

Inheritance mom dad segments

Your father’s chromosomes are shown in the upper portion of the graphic, and your chromosome that you inherited from you father is shown below.

On your copy of your father’s chromosome, I’ve darkened the dark blue and dark pink segments that you inherited from him. You did not receive the light blue and light pink segments. Those segments of DNA are lost to your line, but one of your siblings might have inherited some of those pieces.

Inheritance mom dad both segments

Now, I’ve added the DNA that you inherited from your Mom into the mixture. You can see that you inherited the dark green from your Mom’s father and the dark peach from your Mom’s mother.

Inheritance grandparents dna

These colored segments reflect the DNA that you inherited from your 4 grandparents on this chromosome.

I often see questions from people wondering how they match someone from their mother’s side and someone else from their father’s side – on the same segment.

Understanding that you have a copy of the same chromosome from your mother and one from your father clearly shows how this happens.

Inheritance match 1 2

You carry a chromosome from each parent, so you will match different people on the same segment. One match is to the chromosome copy from Mom, and one match is to Dad’s DNA.

Inheritance 4 gen

Here is the full 4 generation inheritance showing Match 1 matching a segment from your Dad’s father and Match 2 matching a segment from your Mom’s father.

Your Parents Will Have More Matches Than You Do

From your parents’ perspective, you will only match (roughly) half of the DNA with other people that they will match. On your Dad’s side, on segment 1, you won’t match anyone pink because you didn’t inherit your paternal grandmother’s copy of segment 1, nor did you inherit your maternal grandmother’s segment 1 either. However, your parents will each have matches on those segments of DNA that you didn’t inherit from them.

From your perspective, one or the other of your parents will match ALL of the people you match – just like we see in Match 1 and Match 2.

Matching you plus either of your parents, on the same segment, is exactly how we determine whether a match is valid, meaning identical by descent, or invalid, meaning identical by chance. I wrote about that in the article, Concepts: Identical by…Descent, State, Population and Chance.

Inheritance on chromosomes 1-22 works in this fashion. So does the X chromosome, fundamentally, but the X chromosome has a unique inheritance pattern.

X Chromosome

The X chromosome is inherited differently for males as compared to females. This is because the 23rd pair of chromosomes determines a child’s sex.

If the child is a female, the child inherits an X from both parents. Inheritance works the same way as chromosomes 1-22, conceptually, but the inheritance path on her father’s side is different.

If the child is a male, the father contributes a Y chromosome, but no X, so the only X chromosome a male has is his mother’s X chromosome.

Males inherit X chromosomes differently than females, so a valid X match can only descend from certain ancestors on your tree.

inheritance x fan

This is my fan chart showing the X chromosome inheritance path, generated by using Charting Companion. My father’s paternal side of his chart is entirely blank – because he only received his X chromosome from his mother.

You’ll notice that the X chromosome can only descend from any male though his mother – the effect being a sort of checkerboard inheritance pattern. Only the pink and blue people potentially contributed all or portions of X chromosomes to me.

This can actually be very useful for genealogy, because several potential ancestors are immediately eliminated. I cannot have any X chromosome segment from the white boxes with no color.

The X Chromsome in Action

Here’s an X example of how inheritance works.

Inheritance X

The son inherits his entire X chromosome from his mother. She may give him all of her father’s or mother’s X, or parts of both. It’s not uncommon to find an entire X chromosome inherited. The son inherits no X from his father, because he inherits the Y chromosome instead.

Inheritance X daughter

The daughter inherits her father’s X chromosome, which is the identical X chromosome that her father inherited from his mother. The father doesn’t have any other X to contribute to his daughter, so like her father, she inherits no portion of an X chromosome from her paternal grandfather.

The daughter also received segments of her mother’s X that her mother inherited maternally and paternally. As with the son, the daughter can receive an entire X chromosome from either her maternal grandmother or maternal grandfather.

This next illustration ONLY pertains to chromosome 23, the X and Y chromosomes.

Inheritance x y

You can see in this combined graphic that the Y is only inherited by sons from one direct line, and the father’s X is only inherited by his daughter.

X chromosome results are included with autosomal results at both Family Tree DNA and 23andMe, but are not provided at MyHeritage. Ancestry, unfortunately, does not provide segment information of any kind, for the X or chromosomes 1-22. You can, however, transfer the DNA files to Family Tree DNA where you can view your X matches.

Note that X matches need to be larger than regular autosomal matches to be equally as useful due to lower SNP density. I use 10-15 cM as a minimum threshold for consideration, equivalent to about 7 cM for autosomal matches. In other words, roughly double the rule of thumb for segment size matching validity.

Autosomal Education

My blog is full of autosomal educational articles and is fully keyword searchable, but here are two introductory articles that include information from the four major vendors:

When to Purchase Autosomal DNA Tests

Literally, anytime you want to work on genealogy to connect with cousins, prove ancestors or break through brick walls.

  • Purchase tests for yourself and your siblings if both parents aren’t living
  • Purchase tests for both parents
  • Purchase tests for all grandparents
  • Purchase tests for siblings of your parents or your grandparents – they have DNA your parents (and you) didn’t inherit
  • Test all older generation family members
  • If the family member is deceased, test their offspring
  • Purchase tests for estimates of your ethnicity or ancestral origins

Y DNA

Y DNA is only inherited by males from males. The Y chromosome is what makes a male, male. Men inherit the Y chromosome intact from their father, with no contribution from the mother or any female, which is why men’s Y DNA matches that of their father and is not diluted in each generation.

Inheritance y mtdna

If there are no adoptions in the line, known or otherwise, the Y DNA will match men from the same Y DNA line with only small differences for many generations. Eventually, small changes known as mutations accrue. After many accumulated mutations taking several hundred years, men no longer match on special markers called Short Tandem Repeats (STR). STR markers generally match within the past 500-800 years, but further back in time, they accrue too many mutations to be considered a genealogical-era match.

Family Tree DNA sells this test in 67 and 111 marker panels, along with a product called the Big Y-700.

The Big Y-700 is the best-of-class of Y DNA tests and includes at least 700 STR markers along with SNPs which are also useful genealogically plus reach further back in time to create a more complete picture.

The Big Y-700 test scans the entire useful portion of the Y chromosome, about 15 million base pairs, as compared to 67 or 111 STR locations.

67 and 111 Marker Panel Customers Receive:

  • STR marker matches
  • Haplogroup estimate
  • Ancestral Origins
  • Matches Map showing locations of the earliest known ancestors of matches
  • Haplogroup Origins
  • Migration Maps
  • STR marker results
  • Haplotree and SNPs
  • SNP map

Y, mitochondrial and autosomal DNA customers all receive options for Advanced Matching.

Big Y-700 customers receive, in addition to the above:

  • All of the SNP markers in the known phylotree shown publicly, here
  • A refined, definitive haplogroup
  • Their place on the Block Tree, along with their matches
  • New or unknown private SNPs that might lead to a new haplogroup, or genetic clan, assignment
  • 700+ STR markers
  • Matching on both the STR markers and SNP markers, separately

Y DNA Education

I wrote several articles about understanding and using Y DNA:

When to Purchase Y DNA Tests

The Y DNA test is for males who wish to learn more about their paternal line and match against other men to determine or verify their genealogical lineage.

Women cannot test directly, but they can purchase the Y DNA test for men such as fathers, brothers, and uncles.

If you are purchasing for someone else, I recommend purchasing the Big Y-700 initially.

Why purchase the Big Y-700, when you can purchase a lower level test for less money? Because if you ever want to upgrade, and you likely will, you have to contact the tester and obtain their permission to upgrade their test. They may be ill, disinterested, or deceased, and you may not be able to upgrade their test at that time, so strike while the iron is hot.

The Big Y-700 provides testers, by far, the most Y DNA data to work (and fish) with.

Mitochondrial DNA

Inheritance mito

Mitochondrial DNA is passed from mothers to both sexes of their children, but only females pass it on.

In your tree, you and your siblings all inherit your mother’s mitochondrial DNA. She inherited it from her mother, and your grandmother from her mother, and so forth.

Mitochondrial DNA testers at FamilyTreeDNA receive:

  • A definitive haplogroup, thought of as a genetic clan
  • Matching
  • Matches Map showing locations of the earliest know ancestors of matches
  • Personalized mtDNA Journey video
  • Mutations
  • Haplogroup origins
  • Ancestral origins
  • Migration maps
  • Advanced matching

Of course, Y, mitochondrial and autosomal DNA testers can join various projects.

Mitochondrial DNA Education

I created a Mitochondrial DNA page with a comprehensive list of educational articles and resources.

When to Purchase Mitochondrial DNA Tests

Mitochondrial DNA can be valuable in terms of matching as well as breaking down brick walls for women ancestors with no surnames. You can also use targeted testing to prove, or disprove, relationship theories.

Furthermore, your mitochondrial DNA haplogroup, like Y DNA haplogroups, provides information about where your ancestors came from by identifying the part of the world where they have the most matches.

You’ll want to purchase the mtFull sequence test provided by Family Tree DNA. Earlier tests, such as the mtPlus, can be upgraded. The full sequence test tests all 16,569 locations on the mitochondria and provides testers with the highest level matching as well as their most refined haplogroup.

The full sequence test is only sold by Family Tree DNA and provides matching along with various tools. You’ll also be contributing to science by building the mitochondrial haplotree of womankind through the Million Mito Project.

Combined Resources for Genealogists

You may need to reach out to family members to obtain Y and mitochondrial DNA for your various genealogical lines.

For example, the daughter in the tree below, a genealogist, can personally take an autosomal test along with a mitochondrial test for her matrilineal line, but she cannot test for Y DNA, nor can she obtain her paternal grandmother’s mitochondrial DNA directly by testing herself.

Hearts represent mitochondrial DNA, and stars, Y DNA.

Inheritance combined

However, our genealogist’s brother, father or grandfather can test for her father’s (blue star) Y DNA.

Her father or any of his siblings can test for her paternal grandmother’s (hot pink heart) mitochondrial DNA, which provides information not available from any other tester in this tree, except for the paternal grandmother herself.

Our genealogist’s paternal grandfather, and his siblings, can test for his mother’s (yellow heart) mitochondrial DNA.

Our genealogist’s maternal grandfather can test for his (green star) Y DNA and (red heart) mitochondrial DNA.

And of course, it goes without saying that every single generation upstream of the daughter, our genealogist, should all take autosomal DNA tests.

So, with several candidates, who can and should test for what?

Person Y DNA Mitochondrial Autosomal
Daughter No Y – can’t test Yes, her pink mother’s Yes – Test
Son Yes – blue Y Yes, his pink mother’s Yes – Test
Father Yes – blue Y Yes – his magenta mother’s Yes – Test
Paternal Grandfather Yes – blue Y – Best to Test Yes, his yellow mother’s – Test Yes – Test
Mother No Y – can’t test Yes, her pink mother’s Yes – Test
Maternal Grandmother No Y – can’t test Yes, her pink mother’s – Best to Test Yes – Test
Maternal Grandfather Yes – green Y – Test Yes, his red mother’s – Test Yes – Test

The best person/people to test for each of the various lines and types of DNA is shown bolded above…assuming that all people are living. Of course, if they aren’t, then test anyone else in the tree who carries that particular DNA – and don’t forget to consider aunts and uncles, or their children, as candidates.

If one person takes the Y and/or mitochondrial DNA test to represent a specific line, you don’t need another person to take the same test for that line. The only possible exception would be to confirm a specific Y DNA result matches a lineage as expected.

Looking at our three-generation example, you’ll be able to obtain a total of two Y DNA lines, three mitochondrial DNA lines, and 8 autosomal results, helping you to understand and piece together your family line.

You might ask, given that the parents and grandparents have all autosomally tested in this example, if our genealogist really needs to test her brother, and the answer is probably not – at least not today.

However, in cases like this, I do test the sibling, simply because I can learn and it may encourage their interest or preserve their DNA for their children who might someday be interested. We also don’t know what kind of advances the future holds.

If the parents aren’t both available, then you’ll want to test as many of your (and their) siblings as possible to attempt to recover as much of the parents’ DNA, (and matches) as possible.

Your family members’ DNA is just as valuable to your research as your own.

Increase Your Odds

Don’t let any of your inherited DNA go unused.

You can increase your odds of having autosomal matches by making sure you are in all 4 major vendor databases.

Both FamilyTreeDNA and MyHeritage accept transfers from 23andMe and Ancestry, who don’t accept transfers. Transferring and matching is free, and their unlock fees, $19 at FamilyTreeDNA, and $29 at MyHeritage, respectively, to unlock their advanced tools are both less expensive than retesting.

You’ll find easy-to-follow step-by-step transfer instructions to and from the vendors in the article DNA File Upload-Download and Transfer Instructions to and from DNA Testing Companies.

Order

You can order any of the tests mentioned above by clicking on these links:

Autosomal:

Transfers

_____________________________________________________________

Disclosure

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

Genealogy Products and Services

Genealogy Research