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Regarding Shared Ancestor

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  • Regarding Shared Ancestor

    I'm pretty sure this is a very simplistic question, so please bear with me.

    I am going on the assumption that Y-DNA is replicated exactly in the direct male line from one generation to another.

    Based on that, is it possible that people testing I1a2a (I1 and I1d1) and I2a (I2bi) would share the same male ancestor in their direct male lines in the 11th century? Also could others testing H, G, J2, R1b1b2, and T also share that same 11th century ancestor. If the answers is yes for any or all combinations of the cited haplogroups, how is the deviation or change in the Y-DNA accounted for? Ultimately, doesn't the Y-DNA have to pass from one generation to the other unchanged?

    Thank you very much for any time and help you may be able to provide.

  • #2
    I am not quite sure the exact answer to this and I doubt anyone does. When humans left Africa we were all one group no? So how did one Y group turn into another Y group? When did one subclade turn into another? The various allele values and SNP's measured are subject to mutations. Some allele values are more prone to mutation than others. The rates of change of various values are calculated, as best mathematicians can do. So probably the only person who can answer your question more specifically would be perhaps an I group guru who is steeped in statistical analysis.

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    • #3
      Many thanks for your thoughts

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      • #4
        Originally posted by Nicholas3 View Post
        I'm pretty sure this is a very simplistic question, so please bear with me.

        I am going on the assumption that Y-DNA is replicated exactly in the direct male line from one generation to another.

        Based on that, is it possible that people testing I1a2a (I1 and I1d1) and I2a (I2bi) would share the same male ancestor in their direct male lines in the 11th century? Also could others testing H, G, J2, R1b1b2, and T also share that same 11th century ancestor. If the answers is yes for any or all combinations of the cited haplogroups, how is the deviation or change in the Y-DNA accounted for? Ultimately, doesn't the Y-DNA have to pass from one generation to the other unchanged?

        Thank you very much for any time and help you may be able to provide.
        The answer is no. All of those groups, including I1a2a and I2a, branched off from their common ancestor long long before the 11th century A.D.

        I don't have the exact figures, but even I1a2a and I2a, although both in y haplogroup I, parted company long before the 11th century. The most recent common ancestor that all of those haplogroups shared would have belonged to y haplogroup F and probably spent much of his time hiding from sabre-toothed cats.

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        • #5
          Thanks, I appreciate the information and the humor. And while I suspect I know what your answer may be: By extending the logic of your reply, I1a2a and I1d1 would not share an 11th century common ancestor either, correct?

          Thanks again, and take care.

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          • #6
            To elaborate what others have said, there are random, occasional "mistakes" in the dna one passes on to one's descendant. Likely, if one could hypothetically check all the million + bases of the Y chromosome of an 11th century ancestor and one's own, one would find a number of mutations that have accumulated in these centuries.

            The mutations that are used to define haplogroups, like I1a etc, are ancient mutations. The ancestor who fist had them happened, again by chance, to have millions of descendants along the male lineage.

            cacio

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            • #7
              Thank you very much for your words about mutations. Helped to clear things up.

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