Mixing it up with admixtures

No real answer

A reader and Marine Corps officer, Capt. T, wants to know what DNA test might suit his needs. “I would like to know which is the best to find out where my ancestors come from?” he writes. “What countries and continents do I have long lost family from, and what percentage am I and from where. So what do you recommend???”

The problem is that there really isn’t any answer to this question. What we’re talking about here is trying to “measure an individual’s mixed geographic heritage by identifying particular markers, called ancestry-informative markers or AIM, that are associated with populations of specific geographical areas.”1

It’s a pretty easy thing to do if all of your ancestors are from, say, some small island where the population has been stable for generations. But once you start mixing things up, in the process called admixture,2 as populations move and blend, things get dicey really fast.

Add to that the fact that different companies and different labs read the same data in different ways (and look at different base populations) and what you end up with is, well, a mess.

Let me use my own test results as an example. I’ve tested with 23andMe, AncestryDNA, Family Tree DNA, and National Geographic’s new Geno 2.0 project, and there’s really no way to reconcile the different results … except that I’m pretty much boringly European with maybe just a little tinge of this or that tossed in.

At 23andMe, on a global basis, I’m
     • 99.4% European
     • 0.2% sub-Saharan African, and
     • 0.4% “we have no clue” (unassigned).

Looking at it from a regional basis, I’m
     • 76.7% northern European
     • 1.1% southern European
     • 0.5% eastern European
     • less than 0.1% Ashkenazi
     • 21.1% “somewhere-in-Europe” (nonspecific European)
     • 0.2% sub-Saharan African, and
     • 0.4% “we have no clue” (unassigned).

On the sub-regional scale, I’m
     • 9.4% British and Irish
     • 6.4% French and German
     • 1.4% Scandinavian
     • 59.5% “somewhere-in-northern-Europe” (nonspecific northern European)
     • 1.1% “somewhere-in-southern-Europe” (nonspecific southern European)
     • 0.5% eastern European
     • less than 0.1% Ashkenazi
     • 21.1% “somewhere-in-Europe” (nonspecific European)
     • 0.2% sub-Saharan African, and
     • 0.4% “we have no clue” (unassigned).

There isn’t really any good way to compare that to — or judge its validity against — the results from AncestryDNA, where I’m
     • 43% Central European
     • 35% British Isles
     • 15% Scandinavian, and
     • 7% Finnish/Volga-Ural.

And that can’t really be squared except generically with my results at Family Tree DNA, where I’m
     • 85.82% Western European (French, Orcadian, Spanish) and
     • 14.18% European (Tuscan, Finnish, Romanian, Russian), with
     • an 11.72% margin of error on both.

And then there’s National Geographic’s Geno 2.0, where I’m
     • 41% northern European
     • 38% Mediterranean, and
     • 21% southwest Asian.

Which of these is right? My guess is, none of ‘em, entirely, not yet. Every one of these four tests is touted by people who’ll tell you it’s the right one. Yet there are reasons to doubt them all.

So… when you ask which test is recommended, and which is best, the answer really is: none of ‘em — not yet.

The results are getting better, most assuredly, and some of the questions you’re asking may eventually be answered best by the data being collected by the Geno 2.0 project. But none of them, today, is really able to tell you today where your ancestors come from, what countries and continents you might have long lost family from, and what percentage you are or from where. They may promise it, but the delivery just isn’t there.

Not yet.

That doesn’t mean you shouldn’t DNA test. Go right ahead! You can still learn about the very deep ancestry of your YDNA and mtDNA (the types of DNA passed down from father to son to son or mother to daughter to daughter and finally to you). And you can still find cousins and share information by testing your autosomal DNA.

But be realistic about the limitations particularly of the admixture part of autosomal DNA testing, keeping in mind that that part of your results should get better over time.


 
SOURCES

  1. ISOGG Wiki (http://www.isogg.org/wiki), “Genealogical DNA test: Geographical origin tests,” rev. 19 Jan 2013.
  2. There isn’t a good definition of this term online. Wikipedia may be best when it says it “occurs when individuals from two or more previously separated populations begin interbreeding. Admixture results in the introduction of new genetic lineages into a population.” Wikipedia (http://www.wikipedia.com), “Genetic admixture,” rev. 5 Jan 2013.
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3 Responses to Mixing it up with admixtures

  1. Terry Noble says:

    I would be interested to know how the different tests compare with each other on the various markers? Were they all the same? Were there differences?

    • Judy G. Russell says:

      You can’t get the raw data across the board. AncestryDNA, for example, doesn’t make it available at all. It says it will sometime this year, but…

  2. Jeff says:

    A question for the Captain is, “How much research have you done and do you know which country your family came from?”

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