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How Distant of an Ancestor?

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  • How Distant of an Ancestor?

    I'm a newbie to the DNA side of genealogy.

    Can two people who have done autosomal DNA testing show up as a "false positive" match? In other words, they have no reasonably near common ancestor but show up as a match anyway?

    Reason I am asking is that I found someone in my match list that was 5th-8th cousin. I have looked extensively at their tree, and there is certainly nothing in it that would be a reasonable match. What tantalized me was that a big part of their tree was from a place in Switzerland where I and other researchers have suspected distant kinship with the part of Switzerland my kin come from. Thing is, exhaustive studies of the parish registers from there show no link (back to when they started keeping registers). So my supposed common ancestor with the DNA tester would have been pre-1600. It would be great to have evidence for a link through the DNA match, but I am suspicious something so far back would show up as a match.

    Can autosomal testing at all pick up a cousin match that distant?

    I didn't find the right solution from the internet.
    References:Links removed
    Last edited by Darren; 9 September 2017, 12:02 AM. Reason: Please no links to outside company websites

  • #2

    Does it provide you the quality of the match with this cousin (measured in cM)? If it is less than 7 cM there is high probability that it is a false match (IBS - identical by state).


    • #3
      Our DNA had to come from somewhere, so it is likely that SOME autosomal matches are in fact due to a very remote ancestor. The difficulty is in proving it! It would be extremely difficult to prove that a match comes from a particular ancestor in the 17th Century, and not from some other part of the pedigree, because few pedigrees are sufficiently complete that far back.

      The case for a 17th Century match would be stronger if you can find additional matches that share the same segment (in other words, a triangulation group, such that the members of the group match each other on the same segment in all combinations) and if the members of such a group have a common ancestor in their pedigrees.


      • #4
        I don't think the Familyfinder product has a category for 5th-8th cousin. If you tested elsewhere, you may want to contact the company that tested you.

        As previously mentioned, it would be important to find others on the same segment. If the company is Ancestry, they do not have a chromosome browser to back up their claims.