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About STR genetic distance and share common ancestor time

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  • About STR genetic distance and share common ancestor time

    Hi,

    I uploaded STR data from FTDNA to ysearch and I found that the closest match is at Y67 level with genetic distance 15. I'm curious how many generations ago that we shared the same ancestor? Is it possible that we belong to the same subclade and subgroup?

    Thanks.

  • #2
    I found another one

    His genetic distance is 13 at Y67 level

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    • #3
      About 32 generations, if you have the same haplogroup. Choose a generation length you think is correct, 25 or 30 years, multiply that by 32.

      http://www.scs.illinois.edu/~mcdonald/tmrca.htm

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      • #4
        A gd of 13 or 15 on a comparison of 67 markers is quite large. According to FTDNA's guidelines for interpreting 67-marker reuslts ( https://www.familytreedna.com/learn/...s-interpreted/ ), anything over a gd of 10 would be mean that you are almost certainly not related within the genealogical time frame (which FTDNA defines as the most recent 15 generations). FTDNA's TiP tool and other TMRCA (time to most recent common male ancestor) calculators will estimate how long ago you might be related. See https://isogg.org/wiki/Y-DNA_tools Most likely, they will say something like there is a 80% chance you have a common ancestor sometime within the past 20-45 generations, which is not very helpful. All TMRCA calculations are just probabilities and have large margins of error, which get larger the farther back you go.

        Re subclade - You would almost certainly have the same haplotype. "Subclade" is an imprecise term and does not indicate how far down the phylogenetic tree you are talking about. https://isogg.org/wiki/Subclade It is likely that you are part of the same higher level subclades, but have different lower level subclades and almost certainly different terminal SNPs.
        Last edited by TwiddlingThumbs; 13th January 2018, 09:28 AM.

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