Why the Y?

Sometimes people ask me: can Y-DNA testing help my genealogy? (Only men have the Y chromosome, but if you’re female and can test a brother or male paternal cousin, that will work.) If you are looking for an ancestor within the last 300-400 years on your direct paternal line (your father’s father’s father, etc.), this topic is for you.

The test is offered by FamilyTreeDNA (FTDNA). First, you’ll want a basic intro to Y-DNA. If you want to know what a haplogroup is, or the difference between a SNP and a STR, the ISOGG wiki on Y-DNA is always a great place to start. You’ll find an overview of Y-DNA and links to many helpful articles.

Here I am going to focus on what I think is the single most valuable aspect of your Y-DNA results for brick walls or questions in a genealogical time frame. And that is:



Your match list.

Similar to other DNA tests, FTDNA will sort our list of Y-DNA matches by how closely they think those ‘cousins’ may be related to us. With both types of tests, sharing trees with our matches offers the most potential to help our genealogy. But with Y-DNA, we know our matches will be on our direct paternal line and should share our surname if that’s our cultural tradition. See Image 1.

Image 1.


What can my match list tell me?

Here is a sampling of the kinds of results I have seen with my relatives, friends, and clients. I’ve changed some names to protect privacy. You might see results like these if you’re just “fishing” to see what you can discover. You might also see them if you have a case of adoption or other to-be-determined biological surname that you are hoping to resolve.

* Zero matches on Y-37?

I tested my mom’s paternal first cousin Ted. We’re descended from our brick wall ancestor James Hammond, born in Pennsylvania in 1806. Result? Zero matches at Y-37. In fact, zero matches at Y-25, and only one at Y-12. Yikes! Genetic genealogist Maurice Gleeson explains this scenario in this post in his blog DNA and Family Tree Research:

“There are several reasons for why you may have no or few matches:

  • you may be the first person with your Y-DNA signature to do the test;
  • your DNA signature may be very rare because you are the last of your line,
  • or few people with that particular signature are left in the world; you may have unusual mutations which have moved you away from the rest of your group.”

FTDNA told us Ted was predicted to be in the I-M233 haplogroup, so I joined the I-M233 haplogroup project and reached out to its coordinator. He analyzed our data, comparing it to others within that haplogroup, and wrote back that Ted “is most like part of the I-BY3100 branch. You could order just BY3100 or test Big Y to find out for sure just where he is placed in the SNP tree and what other new SNP locations he has. If anyone else tests in the future and matches any of those Novel SNP locations, they will form a new named branch downstream and you have found his closest paternal line relative that has tested.”

Now, I confess, I’m a newbie too when it comes to SNP testing in Y-DNA. To be honest, I don’t think this is going to help me with my Hammond genealogy in the late 1700s. But in the spirit of learning more, I paid the $39 for FTDNA to test Ted’s DNA sample they already have, this time for the BY3100 SNP. That was 3 months ago; we’re still waiting. No hurry. It’s always possible someone in the future will test who is a close enough match to help us too.

* Some matches, including—but not limited to—the expected surname.

We tested W. Kinney at Y-37, and his closest matches were ten men found at a Genetic Distance of 3 (GD=3). That doesn’t refer to generations distant; it means these ‘cousins’ matched him on 34 of 37 markers but not on the other three markers. (So… GD=3.) Eight of the ten men, including the first two, had a surname of Mobley! Uh oh! Just one of those ten was a Kinney. But at least there was one. We decided to upgrade to Y-67 to see if we could learn more. (Y-67 is valuable if you have many matches and want more accuracy in which ones are likely to be more closely related.) At Y-67, David Kinney was the top match, at a Genetic Distance of 4 (i.e. matching on 63 of 67 markers). Brian Kinney matched at GD=5. Thomas Kinney and (anonymous) Mobley matched at GD=6, and seven more Mobleys (and a few other surnames but no Kinneys) matched at GD=7.

So what does all this tell me? FTDNA predicts about a 2/3rd chance that our common ancestor with our top match, David Kinney, is within 8 generations (i.e. mid 1700s). See Image 2 for where to find the TIP icon to click, and see Image 3 for the TIP results between David and W.

Image 2.

TIP icon Apr 2018 blog

Image 3.

TIP image results Apr 2018 blog


So the match list told me two things.

  1. Sometime, long ago, my tree likely had a case of mis-attributed paternity (MPE). This is also sometimes called an NPE: Not the Parent Expected. I might have an ancestor who was a Mobley, whose son was raised in a household of Kinneys and took that surname. Or perhaps that Mobley son just took the surname Kinney because it was his mother’s name, or because he liked it.
  2. Despite that, since my closest matches were all Kinneys and their trees went back two centuries, it looks like my paternal line has been Kinneys for probably at least the last 200 years.

Note: if there were just two or three Mobley’s, I might consider the possibility that the MPE happened on their line: that a Mobley boy was raised a Kinney. But with eight Mobley matches, some of whom trace their paternal line back to the 1600s or 1700s, and three Kinneys who trace their lineage back to just 1807, I suspect my Kinney line came from a Mobley originally.)

For poor Irish Catholic tenant farmers, we’ll probably never find records with the answer. But I feel these results do validate the documentary research I have done on this paternal line—my Kinneys over the last 200 years really were Kinneys. That’s always a plus.

* Some matches on Y-37, but none were the expected surname! Lots of them, however, were a specific unexpected surname.

For this tester, we were expecting the Graham surname, but there were no Grahams on the match list. In fact, the matches were mostly Joyce. At some unknown point in my tree, this tester has an MPE. A man named Joyce probably fathered his Graham ancestor. It could be two or three or four or more generations back. We would definitely want to recruit some more cousins of varying degrees on that line to test to try to figure this out. We might inquire about joining the Joyce surname project too. Surname project administrators can be very helpful.

* Some matches at Y-37, but not the expected surname, and no consistent surname either.

For my Scott cousin, there were no matches closer than the 17 matches at GD=3 (matching 34 of 37 makers), and they had 17 different surnames. Maybe their common ancestor lived back before the time when surnames were common. The tester chose not to upgrade to Y-67, but to wait and see if a closer relative tests someday.

* Some matches at Y-37, with the expected surname, and potential !

Daniel Burket, who married in southwest Ohio in 1820, was probably born in Virginia in the late 1700s. He’s a brick wall. His descendant Arthur took the Y-37 test. He has one match at GD=2, whose most distant known Burkett came from Kentucky. At a GD=3, Arthur has another cousin, whose ancestor Christian Byrket (1732-1801) came from Switzerland to Pennsylvania. These are worthwhile leads. We can try to trace Christian Byrket (and any brothers) forward in time to see if we can discover any reference to  Daniel. Also, Kentucky is not far from where Daniel married; we might expand our search for records referring to Daniel in those nearby Kentucky counties too.

TIP: Just like with autosomal DNA testing, sometimes we get leads to look for new geographic places to look for records, and sometimes we have to try to develop our matches’ trees to find out where we connect.

What about targeted testing?

Suppose I have a hypothesis I want to test. My Nathan Jennings is a census neighbor to three other Jennings households (Amos and David and William) in 1820 Ohio. All but William are age 26-45; William is 45+. Nathan moved away to Indiana in 1825. William died in 1829 and left his land to his two sons Amos and David. I have a theory that my Nathan is Amos and David’s brother, and William’s son. See image 4.

Image 4.

tree blog April 2018

I can do a Y-DNA test on a Jennings male descended from Nathan (Tester A). And I can recruit Jennings males descended from Amos (Tester B) and from David (Tester C). If Amos and David’s descendants match each other, and Nathan’s descendant is not on their match list, then that’s pretty convincing that Nathan is not related to Amos and David, at least not on their Jennings line.

If Testers A and B and C all appear on each other’s match lists, they do share a common direct paternal line ancestor. It doesn’t prove that Nathan is the brother of Amos and David; he could be their cousin for example. But if I’m collecting lots of documents with indirect evidence to build a case, I could include these Y-DNA results as additional evidence that supports my theory.


There is a lot more to learn about Y-DNA. I hope these examples give you an idea on whether it may be a worthwhile option for your genealogy goals.

Ann Raymont © 2018



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