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Excessive yDNA matches

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  • Excessive yDNA matches

    Same uncommon surname for all 3 trees.
    Three genetic family trees that do not appear connected.
    Same common haplogroup R1b in all 3.
    Genealogy can trace all 3 trees back about 300 to 400 years for each tree.
    Results of yDNA 12 markers comparison:
    Tree A – average 6.2 matches
    Tree B – average 460 matches
    Tree C – average 2 matches

    I am trying to understand why tree B has so many more yDNA matches for 12 markers compared to the other two trees.
    Comments please.

  • #2
    Matching is solely based on the values of the first 12 markers. The algorithm doesn't consider the surname or geographic origin of the line.

    So, the answer probably is that the first and last person have at least 2 uncommon marker values for R1b. Since matches at the 12 marker level must be 11/12 or exact, that would mean they get few matches.

    The middle person probably has 11 or all 12 markers with common values and gets lots of matches because of that. This is a situation often seen in R1b men, since many of them have the same common 12 marker results - see Western Atlantic Modal Haplotype (WAMH) at Does the middle person have the WMAH badge which is shown on the page I linked to?

    Do you think that these three men are all related based on the same uncommon surname? That may or may not be borne out by the results, but don't judge based on how many 12 marker matches they have. Matches at less than the 37 marker level (12 or 25 markers) are not considered reliable in many, if not most, cases, especially in R1b men.


    • #3
      Looking at 37 markers for the 3 groups.

      Thanks for your comment MMaddi.
      I don’t believe the 3 groups of men with the exact same surnames are related unless we are going back long before surnames. In the 3 groups I have more then a dozen man so I compared them by groups. All 3 groups started in the USA in the northern eastern area (NH, NY). One man from NH is interesting in the fact even at 37 markers he has over 250 matches (up to 4 steps) while the others that tested at least 37 markers has only a couple of matches each. When we look at 2 steps the number of matches comes down to 6 matches. It appears this one man has some very common yDNA markers.
      It is also interesting to note there are references that indicate the surname in question likely came from another variant name that can be traced back to about the year 1200 in Northern England. (Oxford Dictionary of English Surnames). Testing yDNA of a number of men with the variant surname indicates no genetic relationship but even in this variant surname there appears to be more then one genetic tree.