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How exactly do you calculate TMRCA?

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  • How exactly do you calculate TMRCA?

    I've been interested in this lately.

    Wondering how its done. I've read its not an exact science given all the variables but it is still interesting to find a calculation that places a relation at some point in history!

    Good luck to all

  • #2
    The tool in FTDNA works good for most purposes.

    Just click on the icon in the Y DNA Matches page.

    Here is a comparison between me and my 60/67 match.

    In comparing 67 markers, the probability that Mr. X and Mr. Y shared a common ancestor within the last...
    4 generations is .96%
    8 generations is 15.48%
    12 generations is 46.59%
    16 generations is 74.48%
    20 generations is 90.14%
    24 generations is 96.75%

    I use a range of 25 to 30 for calculating a generation.

    They say:

    Since each marker has a different mutation rate, identical Genetic Distances will not necessarily yield the same probabilities. In other words, even though Mr. Y has a Genetic Distance‡ of 7 from X, someone else with the same Genetic Distance may have different probabilities, because the distance of 7 was prompted by mutations in different markers, with different mutation rates.
    The differences are not large, however.
    Last edited by rucksack; 17 June 2009, 03:15 PM.


    • #3
      The above is regarding TMRCA between two individuals, not between two haplogroups.