The downside of DNA testing
Reader Beth Griffin has run into a snag in using DNA testing to help with her family history. She writes:
I am completely new to DNA use in genealogy. I had my dad submit a DNA sample to ancestry.com paternal lineage testing, 46 marker test. It came back and not a single person on the list shares his last name. People who reportedly share a common ancestor with him as recent as 6 generations back (about 150 years) number about 10, with three of them having the same last name but none of these are dad’s. How is this possible and, can you give a tutorial in layman’s terms about the process and what to look for?
Beth, there are a lot of factors at play here but oh yeah… it sure is possible — and not at all unusual — that there is a mismatch between a person’s DNA and that of others with the same surname, even a common surname. The fact that one test can’t always give us the answer we want — and sometimes not an answer at all — is the downside of DNA testing. That, and the fact that, occasionally, DNA testing can tell us something we might not want to know…
First, let’s do a quick trip through the type of DNA test your Dad did. It’s a test of his YDNA, the gender-linked type of DNA that only men have. So it’s a test that traces only the men in your Dad’s line: his father, his grandfather, his great grandfather and so on. All of the male descendants of these men will also have very similar DNA, so your uncles and male cousins and brothers will similarly have the same or very similar results.1
YDNA generally doesn’t change very much over very long time periods, though there may be small differences from generation to generation and even between brothers or cousins. Because it’s usually pretty stable over the generations, it’s a good way to see if two men could descend from a common ancestor.
For a good overview of YDNA testing generally, let me recommend a couple of websites. First, read up on this kind of testing at the Sorenson Molecular Genealogy Foundation. The animation it offers makes it pretty clear how YDNA works. Then check out the YDNA page of the International Society of Genetic Genealogists Wiki. And you really can’t go wrong with Debbie Kennett’s new book on DNA testing2 or with the older but very readable DNA book by Megan Smolenyak and Ann Turner.3
The key thing to remember here are that YDNA by itself doesn’t tell you who your Dad descends from. It’s only when his DNA is compared to the DNA of other men who’ve tested and that you’e compared the paper trails of these men that you really have any useful information.
When I say “the DNA is compared,” the value of the information you get really depends on four things: how many people have been tested by your testing company (how many results are in the overall database), how many specific DNA areas (called markers) are tested for each person, how many markers are the same between any two or more people tested, and whether those tested share a surname.
The size of the database is a big factor: you want to be able to look at as many different results as you can. The fact that your Dad doesn’t match others with the same surname at Ancestry.com could mean nothing more than that nobody else who shares your father’s bloodline and his surname has tested with Ancestry.
That being said, Ancestry’s YDNA database is big enough to offer value here. Still, it’s not the biggest around and I’d certainly recommend that you test with other companies if you can — and Family Tree DNA has the biggest database around.4
How many markers are tested is also a big factor, and the more tested, the better. That’s because there’s a huge difference between having, say, 12 out of 12 markers that are the same, and having 67 of 67 the same. The significance of a difference in a marker helps figure out what’s called genetic distance, or the number of differences between two sets of results5 — and there again it depends on the number of markers tested: you’re a lot less likely to be related if you only match in 11 of 12 markers than if you only match in 66 of 67 markers. Ancestry’s 46-marker test is a good one, but again if you can afford to transfer his results over and test with FTDNA, 67 or 111 markers is better.
How big the genetic distance is between two people is what lets the testing companies predict how recently you may find a common ancestor. But I want to emphasize here that any statement as to how recently two people who’ve been tested might find a common ancestor is an estimate, not a guarantee. Because YDNA doesn’t change very much, it’s entirely possible to have absolutely identical YDNA results and yet the common ancestor won’t be recent at all but many many generations back. By the same token, it’s entirely possible for two brothers to have one marker out of 46 that’s different from each other.
The different testing companies report matches a little differently, and Ancestry is generally regarded as being… well… let’s just say a little optimistic in saying how recently two people who’ve tested might find a common ancestor. Even though Ancestry predicts that you should find a common ancestor with these other folks in the last six generations (150 years or so), most other testing companies would report the odds of that being the case as much lower.
For example, several of your father’s reported within-six-generations matches have two of the 46 tested markers that are different from your father’s, or a genetic distance of two. Family Tree DNA estimates that the chances that two people with a genetic distance of two will have a common ancestor within the last eight generations are only about 30 percent. It doesn’t go to 50-50 until about 11 generations, and doesn’t hit 75% until 17 generations, give or take a few years.6
So figuring — say — about 25 years per generation, the odds are only 50-50 that the common ancestor between your father and these folks was alive 275 years ago and there’s a one-in-four chance that the common ancestor lived more than 400 years ago.
As you note, however, there are three different people who’ve all tested with Ancestry who all share a last name that’s different from your Dad’s, and they’re all at a genetic distance of one from him. According to the Sorenson folks, that “may indicate a surname change in one line or may be coincidence.”7
To really understand what a surname change means, we need to factor in the history of the use of surnames. Though we can’t imagine anyone not having a surname today, it’s actually a fairly new phenomenon, dating back to only around 1500-1600 for us common folk.8 The poorer and more rural our ancestors, the later historically they were likely to have adopted and used a surname.9
And, when surnames were adopted, there was nothing to stop two brothers from adopting different surnames. Just as an example, one brother might have become a blacksmith and so might have chosen to use the surname Smith. His brother might have taken up farming the family plot and might have chosen simply to be known as the son of his father Will… in today’s terms, Wilson.
Now I don’t want to suggest that surname choice a long time ago is the only reason why two men today might test the same or very similarly and yet not share a surname. Whenever we see this, we also have to consider what’s called a non-paternity event (NPE).
This does NOT mean that one of the mothers somewhere in one of the lines was foolin’ around on the side. Sure, it’s possible that an illegitimate child would use his mother’s surname — I have that situation in my own family.10
But there are many more common explanations for a surname change than illegitimacy. It was very common for a child who was orphaned to be raised by relatives, and that child often chose to use the surname of the family who raised him. A nephew raised by his mother’s brother or his father’s sister’s family, a grandson raised by his mother’s father, might well have used a surname other than the one he was born with. It was also very common for widows with young children to remarry, and for their young sons to use the surnames of their stepfathers.
Was there an NPE in your Dad’s genetic history? I ran that question past two of the smartest genetic genealogists I know, CeCe Moore, who blogs as Your Genetic Genealogist, and Blaine Bettinger, who blogs as The Genetic Genealogist. Both agree that the answer can only come from more testing… but that there is a chance that there might have been.
Your father’s surname is one of the 10 most common in the United States11 and hundreds of people with that surname have tested with Family Tree DNA and joined the testing project for that surname. Your father doesn’t match any of them exactly. Blaine explains why that’s significant: “If there are 200 people with a surname who’ve been tested and another person with that surname tests and doesn’t match any of the others, this is more suggestive than him not matching 20 people with his surname.” He adds that a better question than who your Dad matches is whether there’s anyone who’s already tested that he should be expected to match and doesn’t — a distant cousin, for example.
CeCe notes that the genetic distance between your father and his closest matches in his own surname project is four12 — which drops the odds of a common ancestor but doesn’t eliminate it. It’s possible that the markers that are different are ones that change much more commonly and more quickly than others — which, she notes, appears to be more the case in your Dad’s surname than in the other surname where he shares a close result. In men with that other surname, there is one marker that all of them seem to share, and your father doesn’t. That, she suggests, could mean it’s really not as close a relationship as the numbers may make it seem.
Bottom line: it’s time for more testing to know for sure. But, just in case, you just might want to start talking to those folks from that other surname to see where their roots and yours might be intertwined.
SOURCES
- See generally ISOGG Wiki (http://www.isogg.org/wiki), “Y chromosome DNA test,” rev. 23 Jul 2011. ↩
- Debbie Kennett, DNA and Social Networking: A Guide to Genealogy in the Twenty-First Century (Charleston, S.C. : The History Press, 2012). ↩
- Megan Smolenyak and Ann Turner, Trace Your Roots with DNA: Use Your DNA to Complete Your Family Tree (New York : Rodale Books, 2004). ↩
- Family Tree DNA reports that its database contains results from more than 228,000 YDNA tests and that its overall database is larger than the combined databases of all other testing companies. See “About The Family Tree DNA Database,” Family Tree DNA (http://www.familytreedna.com : accessed 7 Apr 2012). ↩
- Glossary: Genetic Distance, Family Tree DNA (http://www.familytreedna.com : accessed 7 Apr 2012). ↩
- These figures are drawn from some of my own family YDNA tests at Family Tree DNA and are calculated against people sharing a surname. ↩
- “Matching Y-Chromosome DNA Results,” Sorenson Molecular Genealogy Foundation (http://www.smgf.org : accessed 7 Apr 2012). ↩
- Wikipedia (http://www.wikipedia.com), “family name,” rev. 29 Mar 2012. ↩
- See e.g. Sean Murphy MA, “What’s in a Surname?,” Directory of Irish Genealogy (http://homepage.eircom.net/~seanjmurphy/dir/index.htm : accessed 7 Apr 2012). ↩
- See “Friedrike, how COULD you?“, posted 7 Jan 2012, The Legal Genealogist (https://www.legalgenealogist.com/blog : accessed 7 Apr 2012). ↩
- Wikipedia (http://www.wikipedia.com), “List_of_most_common_surnames_in_North_America,” rev. 4 Apr 2012. ↩
- Ancestry and FTDNA test different markers so only 32 of Ancestry’s 46 can be directly compared to those who’ve tested at FTDNA. ↩
Is “GRIFFIN” the surname in question here or is it another surname. Judy, you were not too clear on that. Can you tell us the EXACT Surname of the Father in question here and how many generations back Beth has a paper trail?
Also, you said: “As you note, however, there are three different people who’ve all tested with Ancestry who all share a last name that’s DIFFERENT from your Dad’s.” Can you tell us the EXACT Surnames of these 3 other persons and what the average GD is from the GRIFFIN … what STRs did they differ on … some fast moving ones or slow moving ones?
http://www.americansurnames.us/surname/griffin US Rank for GRIFFIN = 114
You had said: “Your father’s surname is one of the 10 MOST COMMON in the United States ….”
Perhaps you can clarify your assertion. Other sources, such as the one noted above, indicate “GRIFFIN” ranks about 114 in the U.S. One should also look at the Geographical State Clusters in the above link for clues and include variants such as Griffith.
IMHO, instead of considerable noise and refs. about surnames, you might have directed her to: http://gbnames.publicprofiler.org/Map.aspx?name=GRIFFIN&year=1881&altyear=1998&country=GB&type=name and seen that GRIFFIN is pretty much of Welsh origins.
In addition Griffin is a “First Name” as well as a “Last Name”. This line very easily could have come from a Griffin ap William, William ap Griffin, or a Griffin ap Stuart etc.
Also, give some of your other readers a little credit, in addition to CeCe and Blaine, who perhaps having an equal or greater degree of skill than they do in certain areas, on best ways to address Beth’s questions.
What Haplgroup are we talking about? You did not state one and they can be predicted in many cases with a 90%+ probaability with known STRs and various Haplogroup Predictors. http://www.rcasey.net/DNA/R_L21/SNP_Predictor/index.php
Is this “GRIFFIN” on the “R” Tree as I suspect?
Perhaps a rare R-L371 with Welsh origins? http://tech.groups.yahoo.com/group/RL371/ If we had access to the STRs we could help! We know how to ID “Signature STRs” and do our magic.
Please, give us a look at those GRIFFIN markers, or a YSearch ID if there is one. If not you could easily create one or direct Beth how to do it … which I did not see you did.
What Blaine said is not always true: “If there are 200 people with a surname who’ve been tested and another person with that surname tests and doesn’t match any of the others, this is more suggestive than him not matching 20 people with his surname.”
I say that is not completely true. There “are” Rare and Private SNPs which have yet to be discovered via “Walk the Y” AND very Rare ISOGG SNPs with less than 20 “Tested” or “Predicted” members in them. In addition, there are rare Surnames which I work with every day which appear in NO YDNA databases. I would certainly consider those facts prior to jumping off the cliff on NPEs.
In addition, It is very important to state the Race of this Griffin or others you write about. White – Black – Mulatto- Chinese – Native American – Etc. As we know, there are many African Americans who plucked a surname out of thin air such as Booker T. Washington. Contrary to what many believe, African American slaves in the reconstruction period adopted the surname of the slave older in only about 5% of the cases.
I think one of the first steps I would advise Beth is to transfer her results to FTDNA; join the Griffith Surname Group; contact the Group Admin and ask for suggestions. How developed is her paper records … perhaps a Board Certified Genealogist could assist her.
I tried to make my comments constructive and helpful … so don’t please don’t give me too much of tongue lashing :-}
Your comments are fine, George, and perfectly appropriate: no tongue-lashing at all! I didn’t mention the exact surnames because that’s something that both of these families may wish to explore in private before taking so much information public. I’m sure Beth will appreciate your suggestions!
Hi George….I’m Beth Griffin. No, the surname is not Griffin, that is my married name. The surname is Wilson. I had tracked my dad’s surname back to a particular William Wilson who lived in Morgan County, Ga. from about 1814 – 1852. On the 1850 census his birthplace is shown as Virginia. Have been trying to find where in Virginia and anything further back than him for about 15-20 years, off and on. DNA research is just about my last hope and I have recently sent off another DNA test on daddy from Family Tree DNA that will look at 67 markers. I’ve learned they have a big larger database than Ancestry, curious to see if I get similar results there. I have read your comments with much admiration and respect for your knowledge….learning a LOT from the Legal Genealogist and folks like you. Thanks so much for your insights and input!
One more thing….on the ancestry 46 marker test, daddy’s haplogroup comes back as R1b.
Hi Beth,
Did you transfer your dad’s Ancestry Y-DNA test to FTDNA and order an upgrade or did you order an entirely new test?
CeCe
Hi CeCe…to answer your question, I ordered a whole new test from FTDNA with the 67 markers. I also manually entered the results from ancestry.com test into Sorenson’s web site DNA section. Expecting the results of FTDNA any day now.
Hi Beth,
I understand from the recent posts and clarifications your Father (Surname = Wilson) is in the R1b Haplogroup.
Most likely R1b1a2 (SNP = M269).
As seen here, R1b1a2 (SNP = M269), includes a “very large group of persons”: http://xa.yimg.com/kq/groups/30100016/homepage/name/766219?type=sn
From the “Genetic” part of “Genetic Genealogy” Your PRIMARY GOAL at this stage is to ID a Downstream / Descendant Haplogroup BELOW M269 so your Father’s Y-DNA and your research can be limited to a “smaller group of persons” from a Y-DNA Genetic standpoint.
In addition from the “Genealogy” part of “Genetic Genealogy”, we now have some clues to search Georgia and Virginia Wilsons (and their migration patterns) from 1750 to 1850.
If your family is like others I have researched … you could also go back into Pennsylvania in the 1680 to 1750 timeframe … and from there perhaps back into Ireland – England – Scotland. The Haplogroup is a key part of that puzzle.
The goal is to put your Father and his ancestors in a SMALLER BUCKET (i.e.R-M222)versus a LARGE WASHTUB (i.e. R-M269). Once we have him in that SMALLER BUCKET … we can start to look at finer and finer branches on the “R” tree in that Haplogroup and look at possible lineages within “that” smaller Haplogroup
Even with 46 Y-STR Markers I can try to help you find / predict this SMALLER BUCKET HAPLOGROUP but you have to provide info as detailed below:
YSEARCH (part of FTDNA) is the Internet place to LIST your Father’s 46 Y-STR markers right now if you want others to assist and guide you on a gratis basis. It’s also “ONE OF” the “MAJOR SITES” others go to SEARCH for close matches to their Y-STR profile.
Step 1: Go to http://www.ysearch.org/add_start.asp?uid= and list your Father’s 46 Markers.
Step 2: You will also need to follow these instructions to convert some of the Ancestry.com Y-STR Markers into the FTDNA format required at YSearch. http://www.ysearch.org/conversion_page.asp Double Check your entries!
Step 3: Once you get a YSearch ID# …. POST It here on Judy’s website.
The next step will be for some of us to eyeball the markers and use a Haplogroup Predictor to try to predict a Haplogroup.
If we can’t readily predict a Haplogroup … then we will suggest either a FTDNA $29 SNP Test or a $139 DeepClade Test for multiple R-SNPs.
Since you already ordered a Y-67 test at FTDNA … I suggest you also consider at this point ordering a FTDNA DeepClade Test at $139 to “Lab Test” for various R-SNPs. Call FTDNA at(713) 868-1438 and give them your Kit# and tell them you want a R-DeepClade Test.
Hi Beth,
Just to clarify –
If you follow George’s advice and manually enter your father’s Ancestry.com’s Y-DNA values at Y-Search, your father’s value at DYS442 should be 12 and for GATA-H4 also enter 12. When I reviewed his results, I found the conversion tables were a bit confusing for your dad since it appears his test was processed when Ancestry.com was using Relative Genetics to process their DNA tests. In this case, you subtract 1 rather than the 11 that you would normally subtract. If we subtracted 11 as directed, he would have a value of 2 which is not in the known range for that marker.
CeCe
It is so terrific to have folks like you adding so much information here! Thanks!
I was swamped at work so didn’t have time to get any of this done….tomorrow when I get a chance I will indeed follow some of the suggestions given by George and CeCe. Glad you guys understand all this…you kind of lost me there early on! But if Judy says you know your stuff, then you’re okay with me! Thanks so VERY much for your help and interest in this….you guys are awesome!
Beth
Okay George, I did everything you suggested and have received a YSearch User ID ….it is AUHHM. I have not had time to go in and create a password yet and probably won’t tonight. If you need one to get in, let me know. Or you can create one for me and let ME know, if that’s even possible. I’ve got to go now, but thanks again for all of your help and to CeCe also, attempting to follow all instructions as time permits! Cheers!
Beth Griffin
A few years ago I completed FT’s Y-37. I also have done ancestry’s family DNA, sorry name escapes me at the moment, I am a participant in FT’s and Sackett family Assoc. Sackett DNA project, It’s been a surprise to me that I have not been able to resolve what is referred to as the New Haven Sackett line’s origin. It is considered that DNA has proven that that the New Haven, CT and Cambridge/ Boston Sackett lines are not related. It’s left to wonder though, that with all the DNA testing that has occurred in the last 10 years or so no cookie crumb DNA trail has been found regarding who where the New Haven Sackett’s before New Haven? Where they a separate branch of Sackett’s or where they something else? The New Haven Sackett line, depending on your perspective, seems to start or stop in New Haven CT with no previous history.. That of course is an impossibility.
It’s always frustrating when we don’t find the evidence we know has to exist somewhere… but we just have to be patient sometimes until someone from that branch tests to give us the comparator we need.