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sharing a haplogroup

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  • sharing a haplogroup

    I've taken the Big Y test, and one other man shares a confirmed haplogroup with me. Does this mean that we share a male line if we go back far enough? and a surname, if surnames were in use then?

  • #2
    All men share the same paternal ancestor, but if you both have taken Big Y and share the same haplogroup, he is probably your nearest Big Y tested paternal relative. Look at Block tree view. Number of private variants can give you a rough estimate how distant he is. If you both have taken Big Y-700, the rule of thumb is 83 years per SNP. Things get more complex if one of tests if olrder Big Y-500.


    • #3
      If you share the same "terminal SNP", that fact is presumed to mean that there was a shared patrilineal ancestor at some point in the distant past. Exactly how far back, it is usually very hard to guess.

      However, surnames are more difficult. Some men happen to have a "terminal SNP" that places them within a cluster of men who all, or nearly all, have the same surname. If you happened to be a Buchanan, or a descendant of Deacon Edmund Rice, that would probably be your experience. The interpretation is that the original family began using a permanent surname around the time their "terminal SNP" was established. Other men find themselves in a cluster with a wide range of surnames. That was my experience. The interpretation is that the SNP arose well before the families who had it started using permanent surnames, and so that the same SNP has ended up in families with diverse names.

      Permanent surnames passed from father to child are a relatively recent development. While surnames were certainly in use in some areas of Europe as early as the 13th Century or even earlier, they were often used very flexibly, so that different branches of the same family might end up with different surnames. In other areas, the general rule was a patronymic system, so that the "family name" effectively changed with each generation -- the existence of a huge number of surnames that derive from given names (Johnson is the most popular example) is a remnant of the patronymic system.

      Using Y DNA to discover a lost surname is an uncertain proposition. Sometimes it works (Buchanan or Rice, for example), at other times there is no clear result. However, in my case, the uninformative result was still helpful: it told me that my McCoy family is not one of those whose Y DNA has already been studied. I can effectively ignore the genealogies of those other McCoy's, because they are clearly not connected to me.