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1/312.5 to 1/150?

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  • 1/312.5 to 1/150?

    Just some thoughts about YSTR's and population demographics. Does anyone know if there is an established literature on this topic?

    Demographic historian Jan Van Dries estimates that there were approximately 40 million people living in Western Europe at 1500 C.E. This year is often cited as the point at which surnames came into common use. Obviously some names are much older (e.g., O'Cleirigh, etc.), and some societies did not regularize their use until the 1800's. But 1500 C.E. is sometimes given as a useful generalization.

    Let's assume that 1/2 or 20 million were male. Let's also take the perhaps ridiculously conservative assumption that each of them bore a distinctive 25-market Y STR haplotype.

    Finally, let's assume that 2/3 of FTDNA customers have deep ancestry in Western Europe. With current database size of 96k (i.e., 124k total less 28k 12-loci haplotypes=96k), I guess that means that a conservative guess re: probability of a 100% match at 25 + loci are approx. 1 in 312.5 (i.e., 20 million / [96k * 2/3]=312.5).

    But that ignores large standard deviation in reproductive success between individuals in the historical population, degree of kinship within the original 1500 C.E. population, and skewing of FTDNA customer base (i.e., I'm sure that most customers go on to encourage close relatives to participate in projects). Maybe an appropriately conservative estimate of the lower-bound of match probability is 1/150 chance of a 100% match at 25 loci?

    Would 15 million to 30 million men have to participate in order to statistically guarantee one 100% match at 25 loci? What about folks with deep ancestry outside of Western Europe?


    P.S. Have you ever REALLY looked at your hands?

  • #2
    Just read this post to another list that may bear on your question:


    • #3
      Thanks, Tom.

      It'll take me a while to work through the technical lingo, but this is definitely along my train of thought.



      • #4
        The poster's email link is operable. I bet if you posted him he could offer some guidance.