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Ashkenasi Jews genealogy

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  • Ashkenasi Jews genealogy

    Wiki article about Endogamy claims that FamilyTreeDNA has a special algorithm, dealing with the specific problems related to Jewish genealogy. Resulting from a small population there is a lot of "interbreeding" which affects
    results of DNA testing. Does anybody know about it? whom to ask?

  • #2
    My understanding is that FTDNA does use an adjustment in their algorithm for Ashkenazi Jews. That's due to the problems caused by endogamy that make Ashkenazis seem more closely related than they actually are.

    But that's not unusual to FTDNA. 23andMe also makes an adjustment in their relationship algorithm to account for the problem of Ashkenazi endogamy. I don't know about Ancestry.com, but I'd be surprised if they don't make a similar adjustment.

    Each company has their own algorithm, which is proprietary. Because of that, they will not publicly discuss the details of their alogithm.

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    • #3
      Originally posted by MMaddi View Post
      My understanding is that FTDNA does use an adjustment in their algorithm for Ashkenazi Jews. That's due to the problems caused by endogamy that make Ashkenazis seem more closely related than they actually are.

      But that's not unusual to FTDNA. 23andMe also makes an adjustment in their relationship algorithm to account for the problem of Ashkenazi endogamy. I don't know about Ancestry.com, but I'd be surprised if they don't make a similar adjustment.

      Each company has their own algorithm, which is proprietary. Because of that, they will not publicly discuss the details of their alogithm.
      I wonder if Ashkenazis also have higher percentages of FF matches who are X matches for the same reason.

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      • #4
        Originally posted by MMaddi View Post
        My understanding is that FTDNA does use an adjustment in their algorithm for Ashkenazi Jews. That's due to the problems caused by endogamy that make Ashkenazis seem more closely related than they actually are.

        But that's not unusual to FTDNA. 23andMe also makes an adjustment in their relationship algorithm to account for the problem of Ashkenazi endogamy. I don't know about Ancestry.com, but I'd be surprised if they don't make a similar adjustment.

        Each company has their own algorithm, which is proprietary. Because of that, they will not publicly discuss the details of their alogithm.

        There is an excellent review of Ashkenazi endogeny at FTDNA. An article by Paull, Tannenbaum, and Briskman at the Surname Dna Journal "Differences In Autosomal Characteristics Between Jewish And Non Jewish Populations" It concludes that My Origins is more accurate than Population Finder. There is a very brief mention of the Ashkenazi adjustment which involves comparing the first and second longest blocks.
        Last edited by josh w.; 17 January 2015, 07:39 PM.

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        • #5
          Originally posted by josh w. View Post
          There is an excellent review of Ashkenazi endogeny at FTDNA. An article by Paull, Tannenbaum, and Briskman at the Surname Dna Journal "Differences In Autosomal Characteristics Between Jewish And Non Jewish Populations" It concludes that My Origins is more accurate than Population Finder. There is a very brief mention of the Ashkenazi adjustment which involves comparing the first and second longest blocks.
          The article is briefly reviewed in Wikipedia- Genetic Studies Of Jews----autosomal section

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          • #6
            Originally posted by josh w. View Post
            There is an excellent review of Ashkenazi endogeny at FTDNA. An article by Paull, Tannenbaum, and Briskman at the Surname Dna Journal "Differences In Autosomal Characteristics Between Jewish And Non Jewish Populations" It concludes that My Origins is more accurate than Population Finder. There is a very brief mention of the Ashkenazi adjustment which involves comparing the first and second longest blocks.
            The study also found that endogamy increased the number of Ashkenazi matches even when controlling for the number of Jews in FTDNA's sample. It turns out that even small shared chromosome segments may not be due to chance in the Ashkenazi population. The endogamy was mainly the result of having distant rather than recent ancestors in common.

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            • #7
              See also the paper I have just referenced in another thread
              An estimate of Ashkenazi population bottleneck (from Nature Communications)
              http://forums.familytreedna.com/showthread.php?t=36766

              W.

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              • #8
                Originally posted by dna View Post
                See also the paper I have just referenced in another thread
                An estimate of Ashkenazi population bottleneck (from Nature Communications)
                http://forums.familytreedna.com/showthread.php?t=36766

                W.
                Thanks. The Paull paper also pointed to the fairly recent expansion of the Ashkenazi population. The Nature Communications paper, co-authored by Atzmon, supports the view that the Ashkenazi composite is split about 50-50 between Asia and Europe----some earlier studies had produced a higher Asian component.
                Last edited by josh w.; 18 January 2015, 08:50 PM.

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                • #9
                  I have just ordered FF. How will FTDNA know to apply the Ashkenazi algorithm....do I have to inform them to do so?

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