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Segment Too Long For Common Ancestry around 1700?

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  • Segment Too Long For Common Ancestry around 1700?

    This is one of the rare occasions when I've found matches who are in common with each other and who have common ancestors in their trees. For the matches the common ancestors would have been born in the early 1800s, so the segments lengths they share with each other aren't surprising. In order for my mother's ancestors to have crossed paths with the common ancestors these matches have, I would have to go back to around 1700, maybe as late as 1750 and it would have to be in one of my mother's "brick wall" lines.

    Match A, the closest of these matches has tested at FTDNA, where she shares a total of 66 cM, longest segment 33.16 cM with my mother.

    Match A and Mom - chromosome 7 from 2,890,110 to 22,321,142. Length 33.16 cM
    Match B and Mom - chromosome 7 from 15,056,977 to 21,763,530. Length 9.74 cM
    Match A and Match B - chromosome 7 from 15,738,076 to 21,763,530. Length 9.02 cM
    Match C and Mom - chromosome 7 from 5,326,206 to 22,484,519. Length 28.90 cM
    Match A and Match C - chromosome 7 from 4,902,198 to 25,336,560. Length 32.70 cM

    Match A has tested at both FTDNA and at Ancestry and has uploaded to Gedmatch, Match C tested at Ancestry and uploaded to Gedmatch. Match B is only at FTDNA and never answers email, but he does have a tree. So I don't have info on what B and C share.

    On the "Shared" lists Mom has with A and C at Ancestry are 3 other people descended from this colonial American couple. My mother's 1st cousin is also on the shared match list of both A and C. Mom never met this 1st cousin and he doesn't reply to messages.

    Would you say common Ancestry is proven? And do you think the amount of DNA Mom share with match A is a bit high for a common ancestor around 1700?

    Common ancestors would have to be in the line of my mother's one grandparent who had colonial American ancestry. The other grandparent came from France as a child in 1852 and there is none of his descendants who have tested at Ancestry are on the shared match lists of the above matches.

  • #2
    I don't think you can ever quite say proven, but it does look like the most likely scenario. One of my relatives has a match with a 4C2R that looks very like the match with A. Longest segment about 30cM, but they're only on FtDNA and no one else shares that segment. The couple they both descend from married in the 1760s. The match has numerous cousins in the US but if they any are matches I'm not recognising them yet.


    • #3
      Too Long for So Far Back?

      I would say it's unlikely, but definitely possible. I have one French-Canadian match of 71.3 cM, with the longest segment at 28.4 cM. Our most recent common ancestors seem to be eight generations back, but he has an extraordinary amount of endogamy on his maternal side - so much endogamy that 48% of his ancestors circa 1650 were also my ancestors!