Category Archives: TMRCA

Haplogroups: DNA SNPs Are Breadcrumbs – Follow Their Path

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Recently a reader asked some great questions.

If Y-DNA is unchanged, then why isn’t the Y-DNA of every man the same today? And if it’s not the same, then how do we know that all men descend from Y-Adam? Are the scientists just guessing?

The scientists aren’t guessing, and the recent scientific innovations behind how this works is pretty amazing, so let’s unravel these questions one at a time.

The first thing we need to understand is how Y-DNA is inherited differently from autosomal DNA, and how it mutates.

First, a reminder that:

  • Y-DNA tests the Y chromosome passed from father to son in every generation, unmixed with any DNA of the mother. This article focuses on Y-DNA.
  • Mitochondrial DNA tests the mitochondria passed from mothers to all of their children, but is only passed on by the females, unmixed with the DNA of the father. This article also pertains to mitochondrial SNPS, but we will cover that more specifically later in another article.
  • Autosomal DNA is passed from both parents to their children. Each child inherits half of each parent’s autosomal DNA.

Let’s look at how this works.

Autosomal vs Y-DNA Inheritance

Click on image to enlarge

Autosomal DNA, shown here with the green (male) and pink (female) images, divides in each generation as it’s passed from the parent to their child. Each child inherits half of each parent’s autosomal DNA, meaning chromosomes 1-22. For this discussion, each descendant shown above is a male and has a Y chromosome.

This means that in the first generation, which would be the great-grandfather, about 700,000 locations of his green autosomal DNA are tested for genealogy purposes.

His female partner (pink) also has about 700,000 locations. During recombination, they each contribute about 350,000 SNPs (Single Nucleotide Polymorphisms) of autosomal DNA to their child. Their offspring then has a total of 700,000 SNPs, 350,000 green and 350,000 pink contributed by each parent.

This process is repeated for each child, whether male or female (with the exception of the X chromosome, which is beyond the scope of this article), but each child does not receive exactly the same half of their parents’ autosomal DNA. Recombination is random.

In the four generations shown above, the green autosomal DNA of generation one, the great-grandfather, has been divided and recombined three times. The original 700,000 locations of great-grandfather’s green DNA has now been whittled down to about 87,500 locations of his green DNA.

Y-DNA in the Same Generation

Looking now at the blue Y-DNA at left, the Y-DNA remains the same in each generation with the exception of one mutation approximately every two or three generations.

As you can see in the chart, in the exact same number of generations, the Y-DNA of each male, which he inherited from his father:

  • Never recombines with any DNA from the mother
  • Never divides and gets smaller in subsequent generations
  • Remains essentially unchanged in each generation

The key word here is “essentially.”

Y-DNA

The Y chromosome consists of about 59 million locations or SNPs of DNA. STR tests, Short Tandem Repeats, which are essentially insertions and deletions, test limited numbers of carefully curated markers selected for the fact that they mutate in a genealogically relevant timeframe. These markers are combined in panels of either 67 or 111 marker tests available for purchase at FamilyTreeDNA today, or historically 12, 25, 37, 67, and 111 marker panels. The STR test was the original Y-DNA test for genealogy and is still used as an introductory test or to see if a male matches a specific line, or not.

From the STR tests, in addition to matching, FamilyTreeDNA can reliably predict a relatively high-level haplogroup, or genetic clan, based on the frequency of the combinations of those marker values in specific STR locations.

SNPs are much more reliable than STRs, which tend to be comparatively unstable, mutating at an unreliable rate, and back mutating, which can be very disconcerting for genealogy. We need reliable consistency to be able to assign a male tester to a specific lineage with confidence. We can, however, find genealogically relevant matches that may be quite important, so I never disregard STR tests or testers. STR tests aren’t relevant for deeper history, nor can they reliably discern a specific lineage within a surname. SNP tests can and do.

The Big Y-700 SNP test gives us that and more, along with the earlier Big Y-500 test which scanned about 30 million locations. The Big Y-700 is a significant improvement; men can upgrade from the Big Y-500 or STR tests.

The Big Y-700 test scans about 50 million Y-DNA locations, known as the gold standard region, for all mutations. It reports 700 or more STR markers for matching, but more importantly, it scans for all SNP mutations in those 50 million locations.

All mutations are confirmed by at least five positive repeat scans and are then assigned a haplogroup name if found in two or more men.

Y-DNA Testing

If Y-DNA remained exactly the same, then the Y-DNA of men today would be entirely indistinguishable from each other – essentially all matching humankind’s first common ancestor. With no changes, Y-DNA would not be useful for genealogy. We need inherited mutations to be able to compare men and determine their level of relatedness to each other.

Fortunately, Y-DNA SNPs do mutate. Y-DNA is never divided or combined, so it stays essentially the same except for occasional mutations which are inherited by the following generations.

Using SNP markers scanned in the Big Y test, one new mutation happens on the average of every two or three generations. Of course, that means that sometimes there are no mutations for a few generations, and sometimes there are two mutations between father and son.

What this does, though, very effectively, is provide a trail of SNP mutations – breadcrumbs essentially – that we can use for matching, AND for tracking our mutations, which equate to ancestors, back in time.

Estes Male Breadcrumb Trail

I’ve tested several Estes men of known lineage, so I’m going to use this line as an example of how mutations act as breadcrumbs, allowing us to track our ancestors back in time and across the globe.

Multiple cousins in my Estes line have taken the Big Y-700 test.

My closest male cousin matches two other men on a unique mutation. That SNP has been named haplogroup R-ZS3700.

We know, based on our genealogy, that this mutation occurred in Virginia and is found in the sons of Moses Estes born in 1711.

How do we know that?

We know that because three of Moses’s descendants have tested and all three of those men have the same mutation, R-ZS3700, and none of the sons of Moses’s brothers have that mutation.

I’ve created a chart to illustrate the Estes pedigree chart, and the haplogroups assigned to those men. So, it’s a DNA pedigree chart too. This is exactly what the Big-Y DNA test does for us.

In the red-bordered block of testers, you can see the three men that all have R-ZS3700 (in red), and all are sons of Moses born in 1711. I have not typed the names of all the men in each generation because, for purposes of this illustration, names aren’t important. However, the concept and the fact that we have been able to connect them genealogically, either before or because of Y-DNA testing, is crucial.

Directly above Moses born in 1711, you can see his father Abraham born in 1647, along with Moses’ brothers at right and left; John, Richard, Sylvester, and Elisha whose descendants have taken the Big Y-700 test. Moses’s brothers’ descendants all have haplogroup R-BY490 (in blue), but NOT R-ZS3700. That tells us that the mutation responsible for R-ZS3700 happened between Abraham born in 1647, and Moses born in 1711. Otherwise, Moses’s brothers would have the mutation if his father had the mutation.

Moses’s descendants also have R-BY490, but it’s NOT the last SNP or haplogroup in their lineage. For Moses’s descendants, R-ZS3700 occurred after R-BY490.

You can see haplogroup R-BY490 boxed in blue.

We know that Moses and his father, Abraham, both have haplogroup R-BY490 because all of Abraham’s sons have this haplogroup. Additionally, we know that Abraham’s father, Silvester also had haplogroup R-BY490.

How do we know that?

Abraham’s brother, Richard’s descendant, tested and he has haplogroup R-BY490.

However, Silvester’s father, Robert born in 1555 did NOT have R-BY490, so it formed between him and his son, Silvester.

How do we know that?

Robert’s other son, Robert born in 1603 has a descendant who tested and has haplogroup R-BY482, but does NOT have R-BY490 or R-ZS3700.

All of the other Eates testers also have R-BY482, blocked in green, in addition to R-BY490, so we know that the mutation of R-BY490 developed between Robert born in 1555 and his son, Silvester born in 1600, because his other son’s descendant does not have it.

Looking at only the descent of the haplogroups, in order, we have

  • R-BY482 (green) found in Robert born in 1555 and all of his descendants.
  • R-BY490 (blue) found in Silvester born in 1600 and all of his descendants, but not his brother
  • R-ZS3700 (red) found in Moses born in 1711 and all of his descendants, but not his brothers

If we had Estes men who descend from the two additional documented generations upstream of Robert born in 1555, we might discover when R-BY482 occurred, but to date, we don’t have any additional testers from those lines.

Now that we understand the genesis of these three haplogroups in the Estes lineage, what else can we discover through our haplogroup breadcrumbs?

The Discover Reports

By entering the haplogroup in the Discover tool, either on the public page, here, or clicking on Discover on your personal page at FamilyTreeDNA if you’ve taken the Big-Y test, you will see several reports for your haplogroup.

I strongly suggest reviewing each category, because they cumulatively act as chapters to the book of your haplogroup story, but we’re going to skip directly to the breadcrumbs, which is called the Ancestral Path.

The Ancestral Path begins with your haplogroup in Line 1 then lists the first upstream or parent haplogroup in Line 2. In this case, the haplogroup I entered is R-ZS3700.

You can see the estimated age of the haplogroup, meaning when it formed, at about 1700 CE. Moses Estes who was born in 1711 is the first Estes man to carry haplogroup R-ZS3700, so that’s extremely close.

Line 2, R-BY490 occurred or was born about 1650, and we know that it actually occurred between Robert and Silvester born in 1600, so that’s close too.

Scanning down to Line 3, R-BY482 is estimated to have occurred about 1500 CE, and we know for sure it had occurred by 1555 when Robert was born.

We see the parent haplogroup of R-BY487 on Line 4, dating from about 750 CE. Of course, if more men test, it’s possible that more haplogroups will emerge between BY482 and BY487, forming a new branch. Given the time involved, those men wouldn’t be expected to carry the Estes surname, as surnames hadn’t yet been adopted in that timeframe.

Moving down to Line 9, we see R-ZP18 from 2250 BCE, or about 4250 years ago. Looking at the right column, there’s one ancient sample with that haplogroup. The location of ancient samples anchors haplogroups definitively in a particular location at a specific time.

Haplogroup by haplogroup, step by step, we can follow the breadcrumbs back in time to Y-Adam, the first homo sapiens male known to have descendants today, meaning he’s the MRCA, or most recent common ancestor for all men.

Neanderthals and Denisovans follow, but their Y-DNA is only available through ancient samples. They have no known direct male survivors, but someday, maybe someone will test and their Y-DNA will be found to descend from Neanderthals or Denisovans.

Now that we know when those haplogroups occurred, how did our ancestors get from Africa 232,000 years ago to Kent, England, in the 1400s? What path did they take?

The new Globetrekker tool answers that question.

The Breadcrumb Trail

In Globetrekker, each haplogroup’s location is placed by a combination of testers’ results, their identified earliest known ancestor (EKA) country and location, combined with ancient samples, climatic factors like glaciers and sea levels, and geographic features. You can read about Globetrekker here and here.

To view the Globetrekker tool, you must sign it to an account that has taken the Big Y test. It’s a tool exclusively provided for Big-Y testers.

You can click at the bottom of your Globetrekker map to play the animated video.

Beginning in Africa, our ancestors began their journey with Y-Adam, then migrated through the Near East, South Asia, East Asia, then west through central Asia into Europe. The Estes ancestors crossed the English Channel and migrated around what is now England before settling in Deal, on the east coast.

Clicking on any haplogroup provides a description of that haplogroup and how it was placed in that location.

Enabling the option for ancient DNA shows those locations as well, near the haplogroups they represent when the animation is playing.

Clicking on the shovel icon explains about that particular ancient DNA sample, what is known, and how it relates to the haplogroup it’s connected to by a dotted line on the map.

Pretty cool, huh!!

End to End

As you can see from this example, Big Y results are an end-to-end tool.

We can use the Big Y-700 haplogroups very successfully for recent genealogy – assigning testers to specific lines in a genealogy timeframe. Some haplogroups are so specific that, without additional information, we can place a man in his exact generation, or within a generation or two.

Not shown in my Estes pedigree chart is an adoptee with a different surname, of course. We know that he descends from Moses’s line because he carries haplogroup R-ZS3700, but we are still working on the more recent generations using autosomal DNA to connect him accurately.  If more of Moses’s descendants tested, we could probably place him very specifically. Without the Big Y-700 test, he wouldn’t know his biological surname or that he descends from Moses. That’s a HUGE breakthrough for him.

There’s more about the Estes line to learn, however.

If our Estes cousins tested their brothers, uncles or other Estes males in their line, they would likely receive a more refined haplogroup that’s relevant only to that line.

Using Big-Y test results, we can place men within a couple of generations and identify a common ancestor, even when all men within a haplogroup don’t know their genealogical lineage. Using those same test results, we can follow the breadcrumbs all 50 steps back in time more than 230,000 years to Y-Adam.

End to end, the Big-Y test coupled with breadcrumbs in Discover, Globetrekker, and other amazing tools is absolutely the most informative and powerful test available to male testers for their paternal line genealogy.

These amazing innovations tracking more than 50,000 haplogroups across the globe answer the original questions about how we know.

The more people who take or upgrade to the Big Y-700 test, the more haplogroup branches will be added, and the more refined the breadcrumbs, ages, and maps will become. In other words, there’s still more to learn.

Test if you haven’t, and check back often for new matches and breadcrumbs, aka updates.

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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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FamilyTreeDNA DISCOVER™ Launches – Including Y DNA Haplogroup Ages

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FamilyTreeDNA just released an amazing new group of public Y DNA tools.

Yes, a group of tools – not just one.

The new Discover tools, which you can access here, aren’t just for people who have tested at FamilyTreeDNA . You don’t need an account and it’s free for everyone. All you need is a Y DNA haplogroup – from any source.

I’m going to introduce each tool briefly because you’re going to want to run right over and try Discover for yourself. In fact, you might follow along with this article.

Y DNA Haplogroup Aging

The new Discover page provides seven beta tools, including Y DNA haplogroup aging.

Haplogroup aging is THE single most requested feature – and it’s here!

Discover also scales for mobile devices.

Free Beta Tool

Beta means that FamilyTreeDNA is seeking your feedback to determine which of these tools will be incorporated into their regular product, so expect a survey.

If you’d like changes or something additional, please let FamilyTreeDNA know via the survey, their support line, email or Chat function.

OK, let’s get started!

Enter Your Haplogroup

Enter your Y DNA haplogroup, or the haplogroup you’re interested in viewing.

If you’re a male who has tested with FamilyTreeDNA , sign on to your home page and locate your haplogroup badge at the lower right corner.

If you’re a female, you may be able to test a male relative or find a haplogroup relevant to your genealogy by visiting your surname group project page to locate the haplogroup for your ancestor.

I’ll use one of my genealogy lines as an example.

In this case, several Y DNA testers appear under my ancestor, James Crumley, in the Crumley DNA project.

Within this group of testers, we have two different Big Y haplogroups, and several estimated haplogroups from testers who have not upgraded to the Big Y.

If you’re a male who has tested at either 23andMe or LivingDNA, you can enter your Y DNA haplogroup from that source as well. Those vendors provide high-level haplogroups.

The great thing about the new Discover tool is that no matter what haplogroup you enter, there’s something for you to enjoy.

I’m going to use haplogroup I-FT272214, the haplogroup of my ancestor, James Crumley, confirmed through multiple descendants. His son John’s descendants carry haplogroup I-BY165368 in addition to I-FT272214, which is why there are two detailed haplogroups displayed for this grouping within the Crumley haplogroup project, in addition to the less-refined I-M223.

Getting Started

When you click on Discover, you’ll be asked to register briefly, agree to terms, and provide your email address.

Click “View my report” and your haplogroup report will appear.

Y DNA Haplogroup Report

For any haplogroup you enter, you’ll receive a haplogroup report that includes 7 separate pages, shown by tabs at the top of your report.

Click any image to enlarge

The first page you’ll see is the Haplogroup Report.

On the first page, you’ll find Haplogroup aging. The TMRCA (time to most recent common ancestor) is provided, plus more!

The report says that haplogroup I-FT272214 was “born,” meaning the mutation that defines this haplogroup, occurred about 300 years ago, plus or minus 150 years.

James Crumley was born about 1710. We know his sons carry haplogroup I-FT272214, but we don’t know when that mutation occurred because we don’t have upstream testers. We don’t know who his parents were.

Three hundred years before the birth of our Crumley tester would be about 1670, so roughly James Crumley’s father’s generation, which makes sense.

James’ son John’s descendants have an additional mutation, so that makes sense too. SNP mutations are known to occur approximately every 80 years, on average. Of course, you know what average means…may not fit any specific situation exactly.

The next upstream haplogroup is I-BY100549 which occurred roughly 500 years ago, plus or minus 150 years. (Hint – if you want to view a haplogroup report for this upstream haplogroup, just click on the haplogroup name.)

There are 5 SNP confirmed descendants of haplogroup I-FT272214 claiming origins in England, all of whom are in the Crumley DNA project.

Haplogroup descendants mean this haplogroup and any other haplogroups formed on the tree beneath this haplogroup.

Share

If you scroll down a bit, you can see the share button on each page. If you think this is fun, you can share through a variety of social media resources, email, or copy the link.

Sharing is a good way to get family members and others interested in both genealogy and genetic genealogy. Light the spark!

I’m going to be sharing with collaborative family genealogy groups on Facebook and Twitter. I can also share with people who may not be genealogists, but who will think these findings are interesting.

If you keep scrolling under the share button or click on “Discover More” you can order Y DNA tests if you’re a biological male and haven’t already taken one. The more refined your haplogroup, the more relevant your information will be on the Discover page as well as on your personal page.

Scrolling even further down provides information about methods and sources.

Country Frequency

The next tab is Country Frequency showing the locations where testers with this haplogroup indicate that their earliest known ancestors are found.

The Crumley haplogroup has only 5 people, which is less than 1% of the people with ancestors from England.

However, taking a look at haplogroup R-M222 with many more testers, we see something a bit different.

Ireland is where R-M222 is found most frequently. 17% of the men who report their ancestors are from Ireland belong to haplogroup R-M222.

Note that this percentage also includes haplogroups downstream of haplogroup R-M222.

Mousing over any other location provides that same information for that area as well.

Seeing where the ancestors of your haplogroup matches are from can be extremely informative. The more refined your haplogroup, the more useful these tools will be for you. Big Y testers will benefit the most.

Notable Connections

On the next page, you’ll discover which notable people have haplogroups either close to you…or maybe quite distant.

Your first Notable Connection will be the one closest to your haplogroup that FamilyTreeDNA was able to identify in their database. In some cases, the individual has tested, but in many cases, descendants of a common ancestor tested.

In this case, Bill Gates is our closest notable person. Our common haplogroup, meaning the intersection of Bill Gates’s haplogroup and my Crumley cousin’s haplogroup is I-L1195. The SNP mutation that defines haplogroup I-L1145 occurred about 4600 years ago. Both my Crumley cousin and Bill Gates descend from that man.

If you’re curious and want to learn more about your common haplogroup, remember, you can enter that haplogroup into the Discover tool. Kind of like genetic time travel. But let’s finish this one first.

Remember that CE means current era, or the number of years since the year “zero,” which doesn’t technically exist but functions as the beginning of the current era. Bill Gates was born in 1955 CE

BCE means “before current era,” meaning the number of years before the year “zero.” So 2600 BCE is approximately 4600 years ago.

Click through each dot for a fun look at who you’re “related to” and how distantly.

This tool is just for fun and reinforces the fact that at some level, we’re all related to each other.

Maybe you’re aware of more notables that could be added to the Discover pages.

Migration Map

The next tab provides brand spanking new migration maps that show the exodus of the various haplogroups out of Africa, through the Middle East, and in this case, into Europe.

Additionally, the little shovel icons show the ancient DNA sites that date to the haplogroup age for the haplogroup shown on the map, or younger. In our case, that’s haplogroup I-M223 (red arrow) that was formed about 16,000 years ago in Europe, near the red circle, at left. These haplogroup ancient sites (shovels) would all date to 16,000 years ago or younger, meaning they lived between 16,000 years ago and now.

Click to enlarge

By clicking on a shovel icon, more information is provided. It’s very interesting that I-L1145, the common haplogroup with Bill Gates is found in ancient DNA in Cardiff, Wales.

This is getting VERY interesting. Let’s look at the rest of the Ancient Connections.

Ancient Connections

Our closest Ancient Connection in time is Gen Scot 24 (so name in an academic paper) who lived in the Western Isles of Scotland.

These ancient connections are more likely cousins than direct ancestors, but of course, we can’t say for sure. We do know that the first man to develop haplogroup I-L126, about 2500 years ago, is an ancestor to both Gen Scot 24 and our Crumley ancestor.

Gen Scot 24 has been dated to 1445-1268 BCE which is about 3400 years ago, which could actually be older than the haplogroup age. Remember that both dating types are ranges, carbon dating is not 100% accurate, and ancient DNA can be difficult to sequence. Haplogroup ages are refined as more branches are discovered and the tree grows.

The convergence of these different technologies in a way that allows us to view the past in the context of our ancestors is truly amazing.

All of our Crumley cousin’s ancient relatives are found in Ireland or Scotland with the exception of the one found in Wales. I think, between this information and the haplogroup formation dates, it’s safe to say that our Crumley ancestors have been in either Scotland or Ireland for the past 4600 years, at least. And someone took a side trip to Wales, probably settled and died there.

Of course, now I need to research what was happening in Ireland and Scotland 4600 years ago because I know my ancestors were involved.

Suggested Projects

I’m EXTREMELY pleased to see suggested projects for this haplogroup based on which projects haplogroup members have joined.

You can click on any of the panels to read more about the project. Remember that not everyone joins a project because of their Y DNA line. Many projects accept people who are autosomally related or descend from the family through the mitochondrial line, the direct mother’s line.

Still, seeing the Crumley surname project would be a great “hint” all by itself if I didn’t already have that information.

Scientific Details

The Scientific Details page actually has three tabs.

The first tab is Age Estimate.

The Age Estimate tab provides more information about the haplogroup age or TMRCA (Time to Most Recent Common Ancestor) calculations. For haplogroup I-FT272214, the most likely creation date, meaning when the SNP occurred, is about 1709, which just happens to align well with the birth of James Crumley about 1710.

However, anyplace in the dark blue band would fall within a 68% confidence interval (CI). That would put the most likely years that the haplogroup-defining SNP mutation took place between 1634 and 1773. At the lower end of the frequency spectrum, there’s a 99% likelihood that the common ancestor was born between 1451 and 1874. That means we’re 99% certain that the haplogroup defining SNP occurred between those dates. The broader the date range, the more certain we can be that the results fall into that range.

The next page, Variants, provides the “normal” or ancestral variant and the derived or mutated variant or SNP (Single Nucleotide Polymorphism) in the position that defines haplogroup I-FT272214.

The third tab displays FamilyTreeDNA‘s public Y DNA Tree with this haplogroup highlighted. On the tree, we can see this haplogroup, downstream haplogroups as well as upstream, along with their country flags.

Your Personal Page

If you have already taken a DNA test at FamilyTreeDNA, you can find the new Discover tool conveniently located under “Additional Tests and Tools.”

If you are a male and haven’t yet tested, then you’ll want to order a Y DNA test or upgrade to the Big Y for the most refined haplogroup possible.

Big Y tests and testers are why the Y DNA tree now has more than 50,000 branches and 460,000 variants. Testing fuels growth and growth fuels new tools and possibilities for genealogists.

What Do You Think?

Do you like these tools?

What have you learned? Have you shared this with your family members? What did they have to say? Maybe we can get Uncle Charley interested after all!

Let me know how you’re using these tools and how they are helping you interpret your Y DNA results and assist your genealogy.

_____________________________________________________________

Follow DNAexplain on Facebook, here or follow me on Twitter, here.

Share the Love!

You’re always welcome to forward articles or links to friends and share on social media.

If you haven’t already subscribed (it’s free,) you can receive an email whenever I publish by clicking the “follow” button on the main blog page, here.

You Can Help Keep This Blog 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

My Book

Genealogy Books

Genealogy Research