Monday, 16 May 2016

Y-DNA matches with Different Surnames

Why do I have Y-DNA matches that don't have the same surname as me? 

This is a common question that is asked when people first get their Y-DNA results. And there are several explanations for it. The Y-DNA test only compares Y chromosome DNA to other Y chromosome DNA. A “match” between two men usually means one of three Scenarios (bear in mind there are exceptions to every general rule):

Scenario 1. 
The two men are related via a common ancestor who lived some time since the appearance of surnames (e.g. within the last 1000 years or so in Britain & Ireland). And there are several sub-scenarios in this situation:
a) the two men have the same surname - in which case, they are probably related via a common ancestor (who bore that same surname) some time within the last c.1000 years. This is the scenario we are most interested in and forms the basis of surname studies.
b) the two men have different surnames - in which case an NPE may be present i.e. Non-Paternity Event (or Not the Parent Expected). In other words, both men have a common ancestor within the last c.1000 years, but the surname on ONE of their lines (we don’t know which one) has changed over the years because of a secret adoption, or infidelity, or illegitimacy, etc. Postscript: as mentioned in the Comments below, there are many other possible causes for "surname discontinuity". For example, some families adopted new surnames after emigrating to the US, changing the name to perhaps sound more English. And of course some societies adopted inherited surnames quite late (e.g. Turkey in 1934) or not at all (e.g. Iceland, Tibet).
Scenario 2. 
The two men are related before the appearance of surnames (e.g. pre-1000 AD) - in this scenario, the two men will have different surnames (with rare exceptions). This scenario can arise where there has been very little mutation in the DNA over the course of the last c.1000 years or so. Or where there has been a degree of Convergence (see below).

Scenario 3. 
The two men are related but much further back then they look. This is because of Convergence, where the two genetic profiles were identical 10,000 years ago (for example), but then mutate away from each other gradually over the millennia, and then (by chance) start mutating back towards each other so that it looks like the common ancestor is closer than he is (say 500 years ago rather than 10,000 years ago). Convergence is still being studied and not a huge amount is known about how commonly it is encountered. It is likely that it is more common in some haplogroup subclades than in others.


So in the situation where a man matches a man with a different surname, these are either cases of Scenario 1b (NPE) or Scenario 2 (pre-surname match) or Scenario 3 (Convergence). How can you distinguish between these three scenarios? Not easily, but there are certain clues that can help.

If one of the men matches other people with his surname, then it is less likely that his particular surname is the result of an NPE. And if the other man matches nobody with his surname (and there are people with his surname in the FTDNA database that he could potentially match), then the likelihood that an NPE has occurred somewhere along that man's direct male line is higher. On the other hand, if both men match others with their surname, then perhaps this is a case of Convergence.

If the two men have tested to 37 markers (or higher) and are exact matches, then this makes Scenario 1b more likely (i.e. an NPE has occurred somewhere in the past). The likelihood increases if there is an exact match at 67 markers or 111 markers. And on the contrary, the less close the match is (say 4/37 or 3/37), then the more likely this is a case of Scenario 2 (pre-surname match) or Scenario 3 (Convergence).

Looking at the terminal SNP results of a man's matches may give a clue as to which of the three scenarios is most likely to be present. You can examine the terminal SNPs of a man's matches (at the 111 marker level down to the 25 marker level) and see which SNPs are most common among his matches. Then by plotting these SNPs on the haplotree* you can get some indication whether or not there is evidence of Convergence (i.e. the SNPs fall onto different branches of the haplotree) or no evidence of Convergence (all of the SNPs fall onto the same branch of the haplotree). If there is no evidence of Convergence, then this makes Scenarios 1b or Scenario 2 more likely.  In the example below, the terminal SNPs of a man's matches all fall below SNP L226, suggesting that he and his matches all sit on the L226 branch of the haplotree. However, there may be some Convergence further downstream, as two of his matches sit on different branches below SNP FGC5628.

Performing additional downstream SNP testing (e.g. a SNP Pack or Big Y test) will help differentiate between the three scenarios. Here is what you might expect:
Scenario 1b (NPE) - the two men sit on the same downstream branch that is associated with the surname of one of them. The age of the common SNP might be somewhere in the last 1000-2000 years.
Scenario 2 (pre-surname match) - the two men sit on the same branch upstream (i.e. representative of a major subclade of the haplogroup, say L226). The age of the common SNP might be somewhere in the last 2000-8000 years.
Scenario 3 (Convergence) - the two men sit on completely different (i.e. very distantly related) branches of the haplotree and the common SNP is (say) >8000 years old.
If a recent NPE is suspected, autosomal DNA testing can help establish if the two men are closely related (i.e. within the past 5 generations or so).


Using these techniques will help distinguish between the three possible scenarios but in many cases there is unlikely to be a single definitive test that will give you the answer. The best you might be able to hope for is that taking all the evidence together, the balance of probabilities points toward a particular scenario as being the most likely.


Example: Plotting terminal SNP results of a man's matches shows that they all fall below SNP L226
(i.e. no evidence of Convergence before SNP FGC5628)
(click to enlarge)



*I use FTDNA's but you can use others too - ISOGG, the Big Tree, or YFULL's tree







40 comments:

  1. For scenario 1b you should be more specific about promoting adoption of a name based upon geography or profession over infidelity, adoption,..... Specifically mention how surnames were established within Jewish communities in the early 1800's as an example.

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    1. Thanks Wayne - good point. I have added a note to the body of the text above.

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  2. When we can have more men in our surname project on the same playing field of DNA testing, it is going to answer this kind of question, as you suggest. We have already begun doing just that. What a well written blog on DNA and Family Tree Research! I hope others may share this as a learning tool with their group project members, including ours?
    Patty and variant spellings, now including Petty is our surname project.

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  3. A note to scenario 1, in some parts of Europe fixed surnames only became common after the 1500s and in some cases even much later. That means some people are out of luck with relying on surnames with patronyms need a very solid paper trail to find a connection, add to that the difficulty of common name combinations in larger towns, I wouldn't want to be in their shoes.

    I don't have those difficulties with my research (surnames and no patronyms); I know for a fact my line has a documented NPE (or in this case NO paternal event), but I have no close matches so I have no idea where to continue the research. I'm just hoping for a close match someday to find a clue for the papertrail research.

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    1. Very true. My focus is largely on Irish genealogy so most of my ancestors would have surnames that originated around about 1000 AD and which would have come into common usage a century or two later. But, as you say, in many places inherited surnames were adopted relatively late. There are parts of Wales where they were only accepted in the mid-1800's. And there are certain parts of the world where they have not been adopted at all.

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  4. Maurice, This is a nicely succinct and helpful summary of a common question I get. I intend to make your summary available to members of our Rothwell surname group. Thank you!

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  5. This is exactly what I needed, as this is a situation I'm currently tackling. Thanks a mil!

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  6. In scenario 1 it`s possible there could be NPEs in both lines to the common ancestor.

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  7. Interesting article. I am a Marshall, matching no other Marshalls (and there are many). I have a 65/67 match with a Harrison surname. The Harrison match doesn't match any known Harrisons (and there are plenty). So neither of us match our given surname, but we match each other. Anyone want to speculate? -John

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    1. This comment has been removed by the author.

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    2. Same here John. I would really appreciate any ideas at this moment.

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  8. Did you take into account that many mothers gave their own surname to their children rather than that of the father? This has been the case in my family.

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    1. Matronymic naming patterns occur in several cultures and are another potential cause of "surname discontinuity". There is an interesting article about them here ...
      https://en.wikipedia.org/wiki/Matronymic

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  9. Does anyone know the software used to create the phylotree?

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    1. You could contact Alex Williamson directly and ask him. You'll find his email on his website ...
      www.ytree.net

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  10. A very interesting article indeed. May I also suggest a 4. scenario. If you would have scandinavian ancestry, the surename would not be the same along the Y-line. In scandinavia we had patronymicons, men and women had only firstnames by birth, and kept their fathers first name and added sen/son and datter/dotter, to mark the kinship. For example Ola Hanssen/Hanson.

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    1. Thanks for that. Patronymic naming patterns are another cause of "surname discontinuity". I think we need to devote a whole article to the topic and make a comprehensive list of the possible causes of NPE's and "surname discontinuity". I'm looking forward to the new post already!

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    2. Hi my dad I was born in Albania what used to be a part of Greece he says he is Greek,I think there are other ethnicities. My mom's sister's husband did some genealogy on her side we know we have German and Irish he had to stop the search I hear we might have Native American and possibly other ethnicities what is the least expensive way to find out this information can I do it with just one test?

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    3. Hi my dad I was born in Albania what used to be a part of Greece he says he is Greek,I think there are other ethnicities. My mom's sister's husband did some genealogy on her side we know we have German and Irish he had to stop the search I hear we might have Native American and possibly other ethnicities what is the least expensive way to find out this information can I do it with just one test?

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  11. "The two men are related before the appearance of surnames (i.e. pre-1000 AD)" - Most surnames date back to the 15th to 17th century. The connection might be somewhere in the late Middle Ages, not necessarely before 1000 AD!

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    1. Good point. My focus is primarily on Irish & British names, which emerged about 700-1000 years ago. However, the adoption of inherited surnames varied from region to region.

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  12. Whether or not a man who has an NPE in his ancestry matches others with his same surname depends greatly on how many generations back the NPE occurred. In our family we have an NPE that occurred over 5 generations ago snd there are many matches of the same surname but all connected to that same ancester 5 generations back. But of course these men also match many more men of a second surname of the male line prior to the NPE.

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    1. Excellent point, Nancy.

      The incidence of NPE's is estimated to be about 1% per generation, and if surnames arose (in Ireland for example) 1000 years ago, that would mean that the chances of genetic discontinuity with that surname over those 1000 years is somewhere around 30-40% (allowing 33.3 and 25 years per generation to make the maths easy). In other words, the chances that the DNA currently associated with any (Irish) surname originated with the originator of the surname is only about 60-70%.

      And that NPE could have happened anywhere within the last 1000 years - 900 years ago or 90 years ago. And the older the NPE, the more likely there will be descendants carrying the introgressive Y-DNA today. As research progresses, It will be very interesting to see if we can identify "Ancient NPEs". I'm sure they are a lot more common than people imagine.

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  14. Surname patterns are often very irregular with reference to African Americans, in part (but not always) because of the enslavement experience. I know in my own direct paternal lineage three brothers assumed different surnames. So, tracking paternal lineages by surname can be futile to a certain degree. This is equally the case on my maternal side tracing an indirect paternal lineage. One brother assumed "Aldridge" and the another "Hadley". For us, relying on direct lineage surnames can be tricky and not always the best method for tracing ancestry.

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    1. For most African Americans, any family surname that may have existed before the arrival of their ancestors in America has been lost. The only case I know of (and there may be some other rare examples) is the intriguing story of Joe Mozingo, a Los Angeles reporter, who traced his surname back to an African named Edward Mozingo who gained his freedom in 1672 in Virginia. Joe also travels back to Africa and finds that forms of the surname are still in use today. The story is brilliantly told in his engaging book "The Fiddler on Pantico Run" ... http://www.amazon.com/Fiddler-Pantico-Run-African-Descendants/dp/1451627483

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  15. Thank you for reply back. Yes, are many reasons and circumstances that surnames have been changed over time. But for the most part, mine are some what related to each other. At least by allied and related family trees, it would appear. Just have to put them together and track them. Is laborious I know. There are rape, incest, bigamy, desertion, or like Gerald FORD, admiration of his step father, etc. Guardianship's or just plain friendship, as well.

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  16. For African Americans who descend from a white male and a black female from before Emancipation (as one of my family lines does), the surname, in most cases, will be that of the mother. The same would be true in cases of rape by a known or unknown predator. Even after emancipation, many states had laws against mixed marriage, although there we many interracial relationships which carried on (or started) well past the Civil War's end. There are many scenarios, like these, which have resulted in entire lines of families carrying the surname of a matriarch, because (for whatever the reason) children were born out of wedlock. None of these reasons equates to an NPE. Just wanting to point this out.

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  17. Your article helped clear up a few things for me. Having a Greek surname and apparently not having any vestiges of Greek genetically, but rather Welch, has been a bit quandry for me. Having taken the Big Y, with the results indicating my nearest relative, who has also taken the test, has the terminal snp of FGC5494 like myself, with numerous common snp's downstream, has the surname Phillips on Alexs's Big Tree. In addition I match a number of other Phillips, at various levels of testing. Thanks

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  18. My great great gradmother was the wife of Richard O'Farrel what we need to do for DNA testing.

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    1. Hi Tania, if you have male Farrell cousins, start off by doing the Y-DNA-37 test.

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  19. It's been thought that my mom's "physical" father is not the man her mother was married to. (All are deceased). Paternal side of my mom's family (by marriage) is from Ireland (migrated through Canada) and appears from ancestry tracing that the link is very clear back to Ireland. We think that the man who fathered my mother is American Native (Upper Peninsula of Michigan). What is the best test I can take to show American Native lineage and that might disprove lineage on the paternal side from Ireland?

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  20. I have 700 plus matches at the 25 marker level with different surnames I read one comment that stated, Sometimes mutations can occur through many generations in completely unrelated families which result in matching haplotypes in the present time frame. Basically, with enough time and enough possible combinations of mutations, it is possible to end up with matching or closely matching Y-DNA marker results in individuals who do NOT share a common ancestor on the male line.

    What is going on I thought YDNA was more accurate than that,seems I just wasted a lotto money for nothing!

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  21. I was looking for information on Haplo FGC10117 and ran across your comment on Farrow/Farrell made last year. I was recently put into that group as the result of a BigY test, the results of which are currently being analyzed. Did not know where to post this for your Farrell in FGC10117 shoebox. OUt of 25000 folks on my tree I have both Farrow and Farrell. However, the closest is a first cousin of a 1C6XR named Jane Farrow 1802 to 1865 married to a David West in 1818 b 1787 Maryland d 1868 North Carolina. Given I can't get my surname MItchell past 1791 it is hard to say if there are other connections I don't know about yet. Like I said, he can shoebox this info in the event something shows up later. Sorry if this is a little too speculative for purposes of your blog. BTW, only one distant Mitchell line out of thousands of matches. Most are Campbell, Thompson, Rayburn, McCutcheon, Gillespie. Kit 8817.

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    1. If you haven't done so already, you should join the Farrell DNA Project here ... www.familytreedna.com/group-join.aspx?act=groupjoin&group=Farrell

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  22. Looking for Grandfather Smith lineage. Had one Uncle tested at 23and me. No surname matches. But interestingly 4 differentnsurnames show up on one chromosone (lg segs). I have reversed searched the names in GEDmatch, viewed many trees and have found a common pattern. I have been able to link these surnames with a female Smith-between 1700 and 1900. Could be some Maternal nae-changing. But it seems significant to me that these 4 surnames all show a maternal Smith. And to make it even more confusing. There are Smith lines in both Maternal and Paternal Grandparents.They appear to come from the same Smith lineage. What a haystack. Next option - have my Uncle do a Y-37 test. any other ideas out there. My reverse search was through the function in GEDmatch with these 4 surnames and then sub searching the Smith name, then using the User lookup function to see if any DNA is in the GEDcom. Then a one to one match. Have found some Smiths-very distant, but sharing the same Y. I believe I have a start point?? Thanks satinhorseswon@aol.com

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  23. My experience is that getting a match on the surname is the exception. I am involved with testing men on 8 different surnames (my side and my husband's). Only for 2 of the surnames did the men tested get matches to men of the same surname (apart from men I had specifically asked to test).

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  24. I really like the visual in 1b of two men sitting on the same downstream branch....

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  25. WHAT IS A 'REVERSE SEARCH' AT GEDMATCH? HOW IS THIS DONE?

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