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Thread: Just how accurate/recent is GEDmatch? Which calculator/project combo is most recent?

  1. #1

    Just how accurate/recent is GEDmatch? Which calculator/project combo is most recent?

    Just wondering how much GEDmatch results can be trusted, and which calculator/project combo is most recent?

    I uploaded my Ancestry data to GEDmatch and pretty much all of the calculators show results that Ancestry didn't at all (or a much higher %). I've watched a huge guide on GEDmatch and read some websites too but I still don't understand if I'm supposed to be taking all these results with a grain of salt or not (as in, they're super ancient).

    Thanks in advance!

  2. #2
    Registered Users
    Chicago, Illinois
    mixed European
    Y-DNA (P)
    Dad: R1b/L21/DF63
    mtDNA (M)
    Y-DNA (M)
    mtDNA (P)

    United States of America England Wales Sweden Germany
    Which calculator is the most accurate depends on your ethnic background (and to some extent just depends).

    Gedmatch and Ancestry (or the other big commercial tests) aren't doing the same thing. To understand Gedmatch it is helpful to pick a calculator with a spreadsheet and look at the kinds of results that people of various ethnicities typically get. As you will see, people are generally mixed -- someone of, say, 100% Irish background for hundreds of years will still get a percentage of West Med, a percentage of West Asian, often even a small percentage of South Asian or Amerindian (at some levels the results are "just noise" and don't mean anything).

    Ancestry takes their results and uses them to predict what ancestry you actually are -- the country or region in which your ancestors actually lived or came from within the past several hundred years, normally. So the Irish person mentioned above would get a bunch of different components on Gedmatch (depending on the test) and 100% Irish and Scottish on Ancestry (ideally), but both would be correct.

    The oracles give a less sophisticated version of what Ancestry does in that they use the component breakdowns they see and show you what single populations you are closest too (plus the distance) and then some of many, many options for how different breakdowns are likely explanations (how close the distance is shows how close they are likely to be to the real answer, but that something is a closer distance than something else that is already pretty close doesn't mean it's more likely). There are also quirks in how the oracles work and sometimes they use the most extreme populations as bases, which throws off everything. Main thing to realize is that there's nothing magic in some ethnicity or combination being put up as a possible, and you have to look at how the other populations compare to your known to see how representative it is. For example, if within Europe you get a 95% far west population, your 5% will probably be more eastern than a breakdown that started with 80% of some more middle population.

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