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  • Y-DNA chances of success

    I'm wondering how successful others have been with their Y-DNA tests.

    About two-and-a-half years ago, I bought a Y-DNA67 test in hopes of learning about the paternal lineage of my paternal grandfather, who was adopted with no record of his birth father. My closest matches are four men at 37 markers with a genetic distance of 4, so I have no useful leads.

    The best scenario would involve my grandfather's father having another son, who had a son, who had a son--my second cousin. Failing that, I'd hope that my grandfather's father had a brother who had a son, who had a son, who had a son--my third cousin.

    It occurs to me that the farther back I imagine in hopes of finding a common ancestor, the smaller the chance of finding someone with an unbroken male line.

    I'll explain. For a Y-DNA test to match me with a first cousin, I just need him to be the son of my father's brother. Going back another generation, my great-grandfather would have had to have another son, who had a son, who had a son. Going back yet another generation, my great-great-grandfather would have had to have another son, who had a son, who had a son, who had a son.

    However, the farther back I go, the greater the chances of a female child breaking the male line. The chances of finding a connection with an unbroken male line diminish as the number of generations increases.

    So I'm beginning to think that I might never find a true match, and I'm wondering how the rest of you are doing.

  • #2
    Y-DNA chances of success

    Same problem for me - closest matches have a genetic distance of 4 (the test was done on my brother). My father did not have a brother, I did not know for sure if my grandfather had any siblings - I think he did not have a brother. Possibly my great-grandfather did not have any brothers (I know so little about him). My only chance is if my great-great grandfather had any other sons. It is possible he did not, so the trail has gone cold for finding out more.

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    • #3
      Even with Y-111, there are no matches for my McCoy surname, and the closest matches (mostly McMillan) turn out (Big Y) to be separated from me by quite a few SNP's. Big Y, as interpreted by YFull and the "Big Tree" project, was really helpful: I am out on a twig by myself, and can safely ignore all the other McCoy's that have been tested, as well as the McMillans.

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      • #4
        success

        Probably the biggest reason for the lack of closer matches is because few people have done the Y STR tests.

        in America just 1 in 2500 men have taken a Y DNA test. Thus even if you have 300 fourth cousins on your paternal line the odds are against finding them here.

        when STR testing for 111 markers drops below $99 we will probably start finding more matches.

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        • #5
          Re "in America just 1 in 2500 men have taken a Y DNA test. Thus even if you have 300 fourth cousins on your paternal line the odds are against finding them here."

          Yet in my Adams Surname Y-DNA project about 60% find a match
          Per this site
          http://names.mongabay.com/most_common_surnames.htm

          There are 432,738 Adams if half are male and 3/4 of those
          are over 21 that means there are about 150,000 candidates
          with about 500 men tested or 1 in 300
          Hmmm that is a lot different than 1 in 2500
          But still a small sample of all possible.

          And for the Adams surname over half find a match.

          John W

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          • #6
            Originally posted by jova99 View Post
            when STR testing for 111 markers drops below $99 we will probably start finding more matches.
            Dream on!

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            • #7
              It depends what is meant by success.

              If you mean finding a very close match with the same surname, the probability will depend on how many genetically distinct families have ended up with your surname. If you mean, being able to distinguish among distinct families that happen to have the same surname, the probability is much higher.

              Take a look at some different Y chromosome surname projects. For Rice, there are relatively few distinct families, and the odds of a new member being assigned to a known family are relatively high. For Smith, the number of distinct families is apparently too large to be measured, and the odds of a new member being assigned to a known family are very small.

              I haven't found a match for my McCoy family yet, but I find it very useful to know that none of the families that have been tested are good matches. I can ignore them all! That's a lot more than I knew before I was tested.

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              • #8
                Relative to finding like surnames that do not match with
                Y-DNA " I can ignore them all! That's a lot more than I knew before I was tested."

                That is an important point that is often overlooked when
                we talk about Y-DNA testing!
                It has saved me from doing research trips to court houses where I did not have a DNA match but thought I should.
                The cost of just one field trip is much less than the DNA testing.

                John W

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                • #9
                  My datapoint:

                  y-111

                  No matches at 111 markers

                  Two matches at 67 markers; one GD of 6, one GD of 7.

                  Four at 37 markers; all GD of 4; two are from the above, two new

                  Six at 25 markers; one GD of 1 [new], five GD of 2 - Two new names, three repeats from the above.

                  NONE are surname matches but that is expected due to scandinavian use of patronymics.

                  Strangely I'm still glad I did the y-111 and am trying to stay current with SNPs as the haplotree is refined. I'm I2a2b2 [I-L38 with S2606+, F780- and 'almost assuredly' S24121+]

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