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12/12 match ignoring surnames

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  • 12/12 match ignoring surnames

    1. In Scandinavia there is a tradition of patronymic names until recently. So the most recent anchester thing FTDNA operates with is useless for us. So if we ignore last names and only look at the numbers. If two people match 12/12 what is the statistics of relatednes if looking purely at the genetics? What about the statistics for 25/25 and 37/37 and near matches.

    2. Another question is what is the importance of the marker range. I observe that most scientific research is done within the first 12 marker range. Often we see they only have 9 DYS + SNP testing. What if you match a person on the 12 markers but dont match so well at the new 13 (Y-25) but match well at the last 12 (Y-37). Do the 12 markers make the foundation for the additional ones? In other words using a analogy: Do the Y-12 give you the country, the Y-25 give you the state and the Y-37 give you the county? So what if you match the country, but the additional 13 markers in Y-25 is equal to a state in another country? What if the last additional 12 (Y-37) match a county in another country and in another state?

    Hope I managed to express myself clearly in the last question

  • #2
    Noaide, I have checked with Ftdna on the first question regarding Walsh's graphs. The statistical graphs apply whether or not there is a surname match. When there is a surname match the graphs may overestimate the number of generations to the MRCA. That is, the number of generations on the graphs might be reduced if there were a surname match. However the graphs apply if there is not a surname match.

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    • #3
      https://www.familytreedna.com/trs_explain.html

      "Without the genealogy research, and where 2 participants with the same surname match on the 12 marker test, then the scientific answer to the degree of relatedness is that 50% of the time the common ancestor would have occurred within 7 generations, or within approximately 150 years. The range of generations for the common ancestor extends to 76.9 generations, or almost 2000 years for those cases where there is not a surname in common. Therefore the importance of a surname link is paramount to provide a comfortable conclusion of relatedness. Most of the time random matches with people with different surnames do not stand the test for extended DNA testing".

      So we are talking almost 2 000 years?

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      • #4
        Originally posted by Noaide
        [url]Most of the time random matches with people with different surnames do not stand the test for extended DNA testing".
        I think that means exactly what happened to me. I had one 12/12 match, but when the tests were extended to 25 markers, that match was only 22/25. But instead I had a better 23/25 match with someone who I only had a 10/12 match after the first 12 markers. With a close relative, the match would probably had been 25/25 or at least 24/25.

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        • #5
          N3a boat floats

          Noaide,
          I spent a good deal of time last nite reviewing some of the papers you posted on other threads and that I had avoided up to this time cuz I'm basically lazy and going blind <grin>.
          The 12 marker test is essentially a base set that can in most cases be used to estimate a haplogroup (which an SNP test would confirm if need be).
          Even with 37+ markers the conclusion about relatedness is a 'tendency to confirm" as opposed to PROOF whcih it is NOT. The TMRCA is, for most of us, just a feel-good thingy. Some of the PhD math guys seem to be able to treat the times with a confidence I just don't understand .. but hey, I've found out in the past that I don't know everything <grin>.
          I'm matched to a family of suspected cousins at a 24/25 marker level and 32/37 matches on the larger test .. they are from a farm south of Oulu, Finland .. SAVILAAKSO and prior to that SAARALA .. my readings last nite indicated the Savo region of Finland is one that has my Y-STR profile at a 50% level or so.
          Bottom line for all this is .. you need to have a confirmed (thru SNP testing) haplogroup and as many markers as you can afford or find in STR terms and then you wait for the academics in Russia and Scandinavia to go forth ..they indicated in those papers that such was/is underway ..and wait too on the wave of new personal data that NG has prompted to fall back and establish a new level of knowedge about this field.
          With your direct link to Saami ancestry you can sorta rest easy but I'm an adoptee looking for a (probably) Finnish grandfather...gonna be tougher.
          ChrisS

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          • #6
            Noaide, I am well aware of Ftdna's stated position on this issue. All I can say is that Walsh's methodological notes and private correspondence with Ftdna staff support the position I posted above. The apparent contradiction has me puzzled as well.

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            • #7
              Noaide, I am well aware of Ftdna's stated position on this issue. All I can say is that Walsh's methodological notes and private correspondence with Ftdna staff support the position I posted above. The apparent contradiction has me puzzled as well.

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              • #8
                P.S. To further elaborate: The issue is not whether a common surname makes a difference in the number of generations to the MCRA. Presumably common surname does make a difference, although it would be extremely difficult to test this proposition especially for the more distant generations. The issue is whether Walsh's graphs apply only to the common surname condition or whether the graphs apply to both circumstances (common surname and lack of a common surname). In generating the graphs Walsh explicitly chose not to make an adjustment for common surname, possibly because there was a lack of empirical evidence to guide the numerical adjustment to the formula that Walsh employed. If Walsh had made the adjustment then the graphs would only be appropriate if there were a common surname. That is, adjusting for common surname would have resulted in graphs different from the ones Ftdna published.

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