FamilyTreeDNA's Big Y-700 Uncovers Family Relationships

Genetic genealogy provided evidence that three men - all contemporaries who shared the same unusual name - were closely related to each other. But what exactly was the relationship between them?

My fourth great-grandfather was Vachel Kirk. He was born in 1805 in Ohio to Thomas and Sarah (Bonar) Kirk and lived in Licking County where he married Jane Delzell.

He was my family tree’s first Vachel. When I discovered two other men with the same peculiar name living in the same era and in generally close proximity, I had to take a closer look.

• Vachel Kirk #2: Born in 1783 in either Ohio, Pennsylvania, or Virginia (his children couldn’t agree on a location), he married Rachel Hall. Records place him in Fayette County, Pennsylvania through 1815. Beginning in 1820, he appeared in Butler County, Ohio, where he lived the rest of his life.

• Vachel Kirk #3: Born in about 1803 in Ohio, he married Susanna Allstaff. Records place him in eastern Ohio (Belmont, Harrison, then Morgan counties) from 1825 through 1850. In 1855, he moved to Hendricks County, Indiana where he lived the rest of his life.

Mindful of traditional naming patterns, I wondered if they were related.

Y-DNA Testing Establishes a Connection

A third great-grandson of Vachel Kirk #2 took an autosomal and Y-37 DNA test with AncestryDNA and FamilyTreeDNA respectively. The Y-DNA results indicated that he was a close genetic match to a dozen direct male descendants of Thomas Kirk, including his son Vachel. The autosomal test also surfaced more than a dozen matches with descendants of Thomas Kirk. However, the low levels of shared DNA make it difficult to pinpoint a specific family relationship with any certainty.

Encouraged by the initial matches, we upgraded the descendant’s Y-DNA test from Y-37 to Y-111 and then finally Big Y-500. At each level of higher testing, the matches with descendants of Thomas Kirk remained the closest.

In April 2023, I finally located several living direct male descendants of Vachel Kirk #3. One of the men, a descendant of Vachel’s son Isaac Kirk, agreed to a Big Y-700 test.

The results showed that he was a close Y-DNA match to all of Thomas Kirk’s descendants and the descendant of Vachel Kirk #2.

Finally, I had evidence that all three Vachel Kirks were indeed genetically related to each other.

 

Y-DNA Mutation Suggests Close Relationship

The Big Y results for the descendants of Vachel Kirk #2 and #3 suggested a particularly close relationship.

In fact, Vachel #2 and #3 are so closely related that both men belong to their own recently identified haplogroup, branching off from the haplogroup shared by Thomas Kirk and his descendants, including his son Vachel Kirk #1.

Y-DNA matches are defined by naturally yet random occurring mutations in the Y chromosome. These mutations are what allow us to distinguish Kirk men from any other man you pass on the street. They define our paternal ancestry. Men pass these mutations or haplogroup on to their sons which makes it possible for genetic genealogists to trace patterns of relatedness (source: David Vance).

Both Vachel Kirks have a newly identified Y-DNA mutation or haplogroup called R-BY100766 that is unique to them.

So why is this important and what does this reveal about my genealogy?

First, if Thomas Kirk (1778-1846) and Vachel Kirk #2 (1783-1836) were brothers (as I initially theorized), then the R-BY100766 mutation had to occur in Vachel #2 because Thomas’ descendants are negative for this haplogroup. 

However, if the R-BY100766 mutation occurred in a generation before Vachel #2 and he inherited it from his father, then he is NOT a brother to Thomas Kirk who is negative for the mutation.

Focusing on the relationship between Vachel #2 and #3, their shared R-BY100766 mutation suggests that they could be:

Father and son

Hypothetical father and son relationship for Vachel Kirk #2 and #3

Although the Y-DNA indicates it is a genetic possibility, a father and son relationship seems unlikely because Vachel #2 and his wife Rachel Hall eventually named one of their children Vachel in 1834 – over three decades after the birth of Vachel #3 (note that this child is not accounted among the three men referenced in this study). Why would Vachel #2 name two of his sons Vachel – especially if the first son of that name was still alive?

The father/son relationship theory is also undermined by the fact that Vachel #2’s future wife Rachel Hall was only 13 in 1803 when Vachel #3 was born. While not biologically impossible, it seems unlikely that she was his mother. There is currently no evidence that Vachel #2 had a relationship prior to Rachel Hall that resulted in children.

It may also be telling that there were just a dozen autosomal DNA matches between the descendants of Thomas Kirk and the descendant of Vachel Kirk #2. A previous case study examining siblingship between Thomas and Mary (Kirk) Geiger surfaced over 100 paired matches. The fewer number of matches between Thomas and Vachel #2 may be a sign that the relationship was more distant thus explaining the drop off in autosomal matches.

Because of the genealogical unlikelihood that Vachel #3 was a son of Vachel #2, it seems probable the R-BY100766 mutation was inherited from a previous generation, suggesting Vachel #2 and Thomas were not brothers.

A more likely relationship scenario is that Vachel #2 and #3 were:

Uncle and nephew

Hypothetical uncle and nephew relationship for Vachel Kirk #2 and #3

FamilyTreeDNA estimates that the most recent common ancestor of the R-BY100766 haplogroup was born around 1770 which they round down to 1750. Although not conclusive, this age approximation would fit well with the birth of Vachel #2’s father.

This would mean that the R-BY100766 mutation was inherited by Vachel #2 from his father (whose identity we don’t yet know). Vachel #2’s unknown father would then be the grandfather to Vachel #3.

In this theory, Vachel #3 would be the son of an unknown Kirk who was brother to Vachel #2.

What do you think? Does this seem possible to you?

Regardless of the scenario, to surface answers, our path forward will require more testing (both Y-DNA and autosomal). Thank goodness for Black Friday and Cyber Monday deals! 

We're getting closer to definitive answers. One cheek swab and saliva sample at a time.

The Limits of Triangulation

I recently wrote about my difficulties with triangulating DNA cousin matches (see The Trials and Tribulations of Triangulation). Among my challenges were that:

• Most of my DNA matches tested with AncestryDNA, which does not presently give access to the segment data necessary for triangulation.

• Encouraging these cousins to transfer their data to a third-party site that does provide access to segment data is sloooow going. 

I really stepped in it, though, when I said that triangulation was the gold standard for identifying a common ancestor among genetic cousins.

While these challenges are real and resonated with many, genetic genealogists were quick to flag that triangulation “was never the gold standard.”

I’ve spent the last couple weeks boning up on the shortcomings of triangulation to better understand its limits.

Let’s look at those limits in the context of the research question I am investigating.

An 18th Century Siblingship Hypothesis

I believe my fifth great-grandfather Thomas Kirk (1778-1846) was the younger brother of his neighbor Mary (Kirk) Geiger (1774-1832).

From beginning to end, their lives followed similar geographical trajectories:

• Both were born in Virginia
• Both settled in the southern part of Licking County shortly after Ohio gained statehood 
• Both are buried in a small cemetery just yards apart 

I've blogged a considerable amount about Thomas and Mary and the many curious tangential links that led to speculation about a family relationship. Recently, I've turned to genetic genealogy to complement the traditional research.

With more than 40 one-to-one autosomal DNA matches between descendants of Thomas and Mary – and each of those matches sharing amounts of DNA expected for their speculated relationship level if Thomas and Mary were in fact siblings – it seemed there was strong supporting evidence for my theory within reach.

Was there a more conclusive way to interpret what the DNA was telling me and credibly substantiate my hypothesis?

An Example Case Study

I got an idea after I read a case study published in the National Genealogical Society Quarterly.

In a nutshell, a professional genealogist was trying to identify the father of a woman born in 1789. Although traditional genealogy had surfaced a candidate for paternity within her small community, it failed to provide a definitive answer. Turning to genetics, there were significant amounts of shared autosomal DNA between descendants of the woman and her suspected paternal family. To reinforce the argument, these one-to-one matches were supplemented with a handful of triangulated matches among third to sixth great-grandchildren of the alleged father. The case study concluded that the paired and triangulated DNA matches supported the theory that the woman was the daughter of the possible paternal candidate.

This example seemed like a perfect fit that was analogous to my own research hypothesis. If this approach was good enough for a professional case study, then surely it could help me conclude that Thomas and Mary were siblings. I determined I would replicate the model, and search for triangulated matches among the dozens of paired matches already found between Thomas and Mary.

That’s when I crashed head-on with the triangulation trials and tribulations and realized that - while the methodology offers potential value - it was not a gold standard.

Approach with Caution

The odds for finding a triangulated match between descendants of my 5th great-grandfather and his possible sister are not in my favor. In fact, they're downright daunting. I knew that would be the case, but I didn’t realize how poor my chances were.

My DNA is too far removed from Thomas and Mary and their parents, the Most Recent Common Ancestor (MRCA), to be an effective magnet for cousins. As a fifth great-grandson, I could expect – on average - to share less than 1% of Thomas’ DNA (0.78% to be exact).¹ It's easy to imagine how grim the odds are for inheriting any DNA from his parents, my sixth great-grandparents. They're edging on genealogical ancestors who no longer have an imprint on my genetic family tree.²

I needed proxies closer in time to Thomas and Mary who inherited more of their DNA and could boost the odds for matches. Fortunately, several third great-grandchildren of Thomas and Mary are still alive and have tested (all would be fourth great-grandchildren to the parents of Thomas and Mary - the MRCA).

Odds of Inheriting DNA

According to AncestryDNA,³ there's a 100% likelihood that we've inherited DNA from our ancestors up to five generations removed. This means that the tested descendants almost certainly inherited some of their DNA from Thomas and Mary. Although we’re only talking about, on average, 3.12%.

At six generations, AncestryDNA estimates that there’s still a 99.99% chance that we’ve inherited DNA from our ancestors (meaning it’s probable that the tested descendants have inherited DNA from the parents of Thomas and Mary).

Knowing that there’s a 99.99% chance that we inherited DNA dating back at least six generations, but mindful that it’s a slim amount, how likely are these fourth great-grandchildren of the MRCA to share DNA with each other?

Odds of Sharing DNA

According to AncestryDNA, there's a 100% chance that you'll share DNA with siblings through second cousins. Beginning with third cousins there’s a 98% chance, but then the odds dip and decline dramatically for each subsequent generation:

• fourth cousins (71%)
• fifth cousins (32%) 
• sixth cousins (11%) 
• seventh cousins (3.2%) 

Fourth great-grandchildren of the Kirk MRCA would be fifth cousins and, at least at AncestryDNA as a result of their phasing methodologies,⁴ would have a 32% chance of sharing DNA.

While the odds aren't great, they're not entirely insignificant and may explain why I’ve found over 40 one-to-one matches between descendants of Thomas and Mary at AncestryDNA.

Odds of a Triangulated DNA Match

When it comes to triangulation, however, it’s not enough to just find a match. It requires that a group of cousins share the same segments of DNA.

What are the chances of that happening?

Not good.

The process of recombination – how our DNA is randomly mixed up before it’s passed to each new generation – ensures we inherit a mishmash of our parents’ DNA.⁵

This amalgamation of DNA passed from one generation to the next makes it unlikely that three fourth great-grandchildren of the Kirk MRCA would all share overlapping DNA segments.

AncestryDNA found - with a threshold of five centiMorgans (cM) - that three random first cousins shared the same DNA segment 84% of the time. However, when five first cousins were compared, there was only a 40% chance that they each shared the same segment. The likelihood of sharing the same DNA segment among ten first cousins plummeted to 0%.

Even though first cousins will share DNA 100% of the time, the recombination process keeps us on our toes and makes it unlikely that cousins will inherit the exact same pieces of DNA.

Bottom line, the odds are daunting and not in favor of triangulation for recent relationships. Imagine how much grimmer the prospects are for finding triangulated segments among descendants of the Kirk MRCA.

The lesson learned, according to AncestryDNA's computational scientist was that, "We can't rely on those pieces of [matching segments of] DNA in order to bring people together." The odds aren’t in our favor.

And this doesn’t even touch on other complicating factors like

• larger shared segments potentially coming from more distant ancestors, or
• the DNA match actually coming from shared ancestors who are not currently known nor mapped out in the pedigree, or 
• misleading pile ups on certain DNA segments. 

Clearly, triangulation is not the gold standard for identifying and verifying ancestral matches.

The dim probabilities (coupled with challenges inherent to DNA-testing at AncestryDNA) likely explain why I’ve only found, to-date, two triangulated matches between descendants of Thomas and Mary from the 40+ paired matches.

I'm not discounting these triangulated matches or the value of triangulation in certain cases, but I am meditating on alternative approaches to determine how best to leverage these DNA matches to prove or disprove that Thomas Kirk and Mary (Kirk) Geiger were siblings.

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[1] https://dna-explained.com/2017/06/27/ancestral-dna-percentages-how-much-of-them-is-in-you/
[2] https://gcbias.org/2013/11/11/how-does-your-number-of-genetic-ancestors-grow-back-over-time/
[3] https://www.ancestry.com/academy/course/ancestry-dna-circles
[4] https://cruwys.blogspot.com/2016/01/autosomal-dna-triangulation-part-2.html
[5] https://cruwys.blogspot.com/2016/01/autosomal-dna-triangulation-part-1.html

The Amalgamation of Me: DNA Ethnicity Estimates

I'm a zealous convert when it comes to incorporating DNA into traditional genealogy. As a tool, it empowers research in ways never before imagined.

I speak from experience.

Genetic genealogy confirmed a long-suspected Non-Paternal-Event (NPE) in my own family tree (that four-part saga begins with A Family History Mystery Revealed). 

DNA connected me to my biological patrilineal pedigree, bypassing a fiction that had been touted as truth and perpetuated for more than 80 years. Without the insights from genetic cousin matching, it's doubtful that the truth would have ever surfaced or been confirmed through conventional paper trail research. 

Family historians imperil their own research when neglecting genetic testing.

But that's not what prompts many people to test

Let's face it, many consumers are not interested in - or even aware of - the full potential of DNA testing. Instead, they're lured to spit in tubes by flashy promotions that distill ancestral genetic testing down to simple geographical ethnicity estimates.

Why bother trawling through vital records, census enumerations, or tax and land deeds if you can get answers from salivating? Just wait a couple weeks and let the lab tell you who you are and where your people come from.

And I get it. To the average Joe, the appeal of this aspect of DNA testing fits with how we often casually discuss ancestry. 

"Where do your people come from?"

Which is met with an Atlas-grab of countries peppered with eyebrow-raising stories of a Mayflower voyage to the Americas and, for good measure, lineage anchored to [insert royal monarch here].

Of course, the DNA estimates are only as accurate as the sample populations against which your saliva is compared. They are interesting, for sure, but not something that has served my researched genealogy in meaningful ways. Not yet, anyway.

Don't get me wrong, I'm fine with the glossy appeal of ethnicity mapping features. After all, it's probably why millions of folks have tested who wouldn't have otherwise. Who knows, maybe one among them will help me bust through a research brick wall.

While I've long disregarded the ethnicity mapping featured by the companies with which I've tested, the recent results from a fourth company finally piqued my curiosity. 

Where do my people come from?

I've taken autosomal DNA tests with four of the leading genetic genealogy providers. How did my results stack up against each testing company? 

The results, while interesting, highlight the varying interpretations a tester is apt to get.

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AncestryDNA

 
• England, Wales & Northwestern Europe: 69%
• Ireland and Scotland: 21%
• Greece and the Balkans: 3%
• Sweden: 2%
• Norway: 2%
• Italy: 1%
• Portugal: 1%
• Cameroon, Congo, and Southern Bantu Peoples: 1%

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Family Tree DNA

• West and Central Europe: 59%
• British Isles: 39%
• Finland: < 1%
• West Africa: < 2%

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23andMe

• British & Irish: 53.9%
• French & German: 11.2%
• Italian: 4%
• Scandinavian: 3.3%
• Iberian: 1.9%
• Balkan: 1.8%
• Sardinian: 0.2%
• Finnish: 0.1%
• Broadly Northwestern European: 18.3%
• Broadly Southern European: 2.2%
• Broadly European: 1.7%
• West African 0.7%
• North African & Arabian: 0.3%
• Southeast Asian: 0.1%
• Broadly East Asian & Native American: 0.1%

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MyHeritage

• English: 31.7%
• Scandinavian: 26.7%
• Irish, Scottish, and Welsh: 21.9%
• Iberian: 14.9%
• Italian: 4.8%

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There's a lot of variation across the European continent, which is likely the result of each company's differing sample populations against which my DNA is compared as well as their proprietary behind-the-scenes numbers-crunching. 

I think the results are clear: I'm an amalgamation of Europe with consensus on strong concentrations in Britain (God save the Queen!) and Ireland. My Italian ancestry is interpreted in varying fashions, and the Scandinavian consistently finds its way into the tally. 

Taken on the whole, I see where my paper trail dovetails with these estimates. But my research path isn't directed by these maps.

How do your estimates compare across companies? In what ways do ethnicity estimates inform your genealogy?