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Thread: Pile-up related matches at commercial DNA companies (23andme, Myheritage, FTDNA...)

  1. #1
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    Pile-up related matches at commercial DNA companies (23andme, Myheritage, FTDNA...)

    So I finally got one (Romanian), out of three (a Romanian, a Iranian-Jewish and a Corsican-French match), of my "excessive matches" on the 10th chromosome to upload to Gedmatch.

    The contrasting results from Gedmatch are interesting to say the least.

    Here is our matching segments over at 23andme:



    Here we are again over at Gedmatch (I lowered the setting to 5cM and 250SNP so as to include any micro segments):


    Next I ran my other relatives to check what matches they might have with this person (I only posted the ones who have a match):

    Brother 1 (FTDNA tested):


    Brother 2 (FTDNA tested):


    Maternal uncle (23andme V2 tested):


    Paternal aunt (23andme V2 tested):


    So it seems Gedmatch screens for "excessive matches" on the 10th chromosome, but 23andme does not..
    https://isogg.org/wiki/Identical_by_...ss_IBD_sharing :
    Last edited by evon; 01-25-2018 at 12:24 PM.

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  3. #2
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    I have spotted another instance of "fake" matches. This time via Myheritage, and located on the 15th chromosome.

    They are usually listed as 3-5th cousin:


    On a confirmed "excessive matching spot" on the 15th chromosome:


    I have not looked into all of the "in common matches", but the ones I did look at are all British..


    PS: maybe the moderators can change the thread title to; "fake" matches via commercial DNA companies.
    Last edited by evon; 02-08-2018 at 02:49 PM.

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     CyrylBojarski (12-02-2020)

  5. #3
    Except my North African, Iberian and Sephardic MyHeritage matches, all my other matches share with me around 8cM on the chromosome 8. Sometimes, we don't even have any "shared ethnicity", which is obviously weird.. I wonder if it's a fake matching segment or a really ancient shared segment with those people (all of European heritage).

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    Last edited by mershechu; 02-08-2018 at 03:23 PM.

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    Quote Originally Posted by mershechu View Post
    Except my North African, Iberian and Sephardic MyHeritage matches, all my other matches share with me around 8cM on the chromosome 8. Sometimes, we don't even have any "shared ethnicity", which is obviously weird.. I wonder if it's a fake matching segment or a really ancient shared segment with those people (all of European heritage).

    fake match.jpg
    Admixture has little to do with matches, these are two different things (so they are not fake just because you dont have common admixture % with them)..

    But there is an "excessive spot" on the 8th chromosome:


    So you should check if these matches overlap with the "excessive spot".
    Last edited by evon; 02-08-2018 at 03:29 PM.

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  8. #5
    Quote Originally Posted by evon View Post
    Admixture has little to do with matches, these are two different things (so they are not fake just because you dont have common admixture % with them)..

    But there is an "excessive spot" on the 8th chromosome:


    So you should check if these matches overlap with the "excessive spot".
    Oh ! This is really interesting, thanks for enlightening me !
    But can you please explain how can I match people over 7cM without any "shared ethnicity admixtures" ?
    I also noticed (but it's maybe a pure coincidence) that I shared "ethnicity admixtures" with most of my matches who overlap with these excessive spots AND with additional shared cM around these spots (mainly on the 8th and 10th chromosomes)
    Last edited by mershechu; 02-08-2018 at 03:49 PM.

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    Quote Originally Posted by mershechu View Post
    Oh ! This is really interesting, thanks for enlightening me !
    But can you please explain how can I match people over 7cM without any "shared ethnicity admixtures" ?
    I also noticed (but it's maybe a pure coincidence) that I shared "ethnicity admixtures" with most of my matches who overlap with these excessive spots AND with additional shared cM around these spots (mainly on the 8th and 10th chromosomes)
    The simple answer is that admixture calculations are just estimations (but it ultimately has to do with methodology differences between calculating matches and admixture), which should be understood as flawed at best.

    You can read about it here as an example. But it is better that you google these terms to get a better handle om it as there are many aspects of DNA admixture and segment matching (it also depends on the various DNA company etc)..

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    Quote Originally Posted by evon View Post
    I have spotted another instance of "fake" matches. This time via Myheritage, and located on the 15th chromosome.

    They are usually listed as 3-5th cousin:


    On a confirmed "excessive matching spot" on the 15th chromosome:


    I have not looked into all of the "in common matches", but the ones I did look at are all British..


    PS: maybe the moderators can change the thread title to; "fake" matches via commercial DNA companies.
    I can add that I also have a Russian and Hungarian match on the same spot at roughly the same 20+ cM as the British matches..

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    Quote Originally Posted by evon View Post
    I have spotted another instance of "fake" matches. This time via Myheritage, and located on the 15th chromosome.

    They are usually listed as 3-5th cousin:


    On a confirmed "excessive matching spot" on the 15th chromosome:


    I have not looked into all of the "in common matches", but the ones I did look at are all British..


    PS: maybe the moderators can change the thread title to; "fake" matches via commercial DNA companies.
    Interesting you write about this one - my father matches a bunch of mostly British looking individuals at this pile-up area, too. I don't think all of them were British. I ran some admixture tests on a list of the matching persons and noticed that a lot of them seemed to have slightly elevated South Asian scores, like 1% to 3% on Eurogenes K13 and PuntDNAL K13, but tended to match a British single population the best. Did you happen to do that, too, and did you happen to notice the same thing? The area itself didn't seem to be anything but typical Western European looking. I know that it is difficult to determine recent ancestry with these kinds of areas, but they can be handy if associated with some specific ethnicity. I wanted to write you about it because the South Asian minor admixture kept popping up and thought you may know something about it with your Roma research.

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    Quote Originally Posted by randwulf View Post
    Interesting you write about this one - my father matches a bunch of mostly British looking individuals at this pile-up area, too. I don't think all of them were British. I ran some admixture tests on a list of the matching persons and noticed that a lot of them seemed to have slightly elevated South Asian scores, like 1% to 3% on Eurogenes K13 and PuntDNAL K13, but tended to match a British single population the best. Did you happen to do that, too, and did you happen to notice the same thing? The area itself didn't seem to be anything but typical Western European looking. I know that it is difficult to determine recent ancestry with these kinds of areas, but they can be handy if associated with some specific ethnicity. I wanted to write you about it because the South Asian minor admixture kept popping up and thought you may know something about it with your Roma research.
    I have noted that the matches on this particular segment are from all over Europe, which fits considering it is an "excessive spot". Therefore they are basically worthless for tracking ones own ancestry. So my advice would be to be aware of these "excessive spots" and to not look for any meaningful DNA clues among them...

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    Quote Originally Posted by evon View Post
    I have noted that the matches on this particular segment are from all over Europe, which fits considering it is an "excessive spot". Therefore they are basically worthless for tracking ones own ancestry. So my advice would be to be aware of these "excessive spots" and to not look for any meaningful DNA clues among them...
    I don't agree that they are worthless for general ancestry. I agree they aren't worth much for recent ancestry. For example, one of my father's pile ups matches to a list of persons who almost all are Ashkenazi or Sephardic. They may not be recently related because it is a pile up, but he likely has a recent ancestor of that type or the pile up wouldn't be present.

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