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Those dratted ethnicity percentages

It’s a question that just won’t go away.

percentNo matter how many times The Legal Genealogist warns — and most others interested in genetic genealogy agree — that the ethnicity estimates provided by DNA testing companies are not all that accurate,1 people still want to know:

• What’s the best testing company to find out where in Africa my people came from?

• What’s the best testing company if I think I have Native American or American Indian ancestry and I want to know what tribe?

• What’s the best testing company if I’m English, or German, or Russian, or Italian, or…?

I really do understand the desire to know. I am sitting at an airport waiting to board a flight that will take me to meet a great nephew2 for the first time, and like many of the youngest members of my family he is adding an amazing element of diversity to our family’s ethnic mix. This little boy is contributing Korean genes to our mix, joining a cousin who has brought in African genes and others whose origins are spanning more and more of the globe.

Someday, I surely hope, young Jack will want to know more about his ancestry, and I hope will want to look at the clues hidden in his genes. And, I expect, I will hear the question from him that I hear from other researchers today: “what’s the best testing company for…”

Maybe by the time Jack is old enough to ask the question, and understand the answers, there will be an answer to that question that will satisfy him, and me, and you, and everyone else who wants to know about the evidence of our ancestry that may be found in our genetic makeup.

But the simple fact is, that day isn’t here yet.

We have to keep in mind what these admixture tests do: they take the DNA of living people — us, the test takers — and they compare it to the DNA of other living people — people whose parents and grandparents and, sometimes, even great grandparents all come from one geographic area. Then they try to extrapolate backwards into time. Nobody is out there running around, digging up 500- or 1,000-year-old bones, extracting DNA for us to compare our own DNA to.

So coming up with these percentages in these tests requires this fundamental assumption: that the DNA of the reference populations — those groups whose parents, grandparents, great grandparents and more all come from the same area — is likely to reflect what we might see if we could test the DNA of people who lived in that area hundreds and thousands of years ago.

In other words, these percentages are:

• estimates,

• estimates based on comparisons not to actual historical populations but rather to small groups of people living today, and

• estimates based purely on the statistical odds that those small groups tell us something meaningful about past populations.

In fact, because of these limitations, the very best we can get right now shouldn’t even be called an estimate of the percentage of our genes that come from a specific country. At best it might be called a guesstimate.

The reality is that these percentages are dynamite at the continental level: European versus African versus Asian. And they’re pretty good at identifying descent from populations that are fairly isolated and not mixed with other similar populations. But for the most part they’re really a crap shoot when you try to distinguish, say, English from Irish from Welsh.

These limitations are true of all of the testing companies. I’ve tested with them all, and my own results are — literally and figuratively — all over the map. I’m German with some companies, not German at all with another. Largely Scandinavian with one, only slightly Scandinavian with the others.

Just as one example, 23andMe says I am a little more than four percent Scandinavian. Family Tree DNA says I am about 12 percent Scandinavian. And AncestryDNA says I am more than 30 percent Scandinavian. I have no known Scandinavian ancestors. None at all. So which company is right? Or are they all wrong? I don’t know, and unless they start digging up those old bones, I’m not convinced I’ll ever know for sure.

So what’s the answer to the “what’s the best company” to test with question? It has to be the same answer I give about any DNA testing: test with every company you can afford to test with. You will see differences in the ethnicity estimates from each company you test with, and you can make your own decision about which set of estimates you think most closely approaches the truth.

If one of the three major testing companies detects 0.01 percent Native American and you want to believe it, you will choose that company’s results. If another detects 2.2 percent sub-Saharan African and you want to believe that, you will choose that company’s results.

In the final analysis, because the science is simply not there yet to support percentages at the country or tribal level, we’re all left choosing to accept what we want to believe.

And that’s the best we can do with tests that just aren’t all that good at detecting ethnicity on a country-by-country basis. And I can only repeat what I’ve said before: DNA testing for genealogical purposes is a wonderful tool. But people get disappointed when they see these percentages and they don’t match up to their own paper trail and don’t match up from company to company. And when they get disappointed, they may lose interest in genealogy or in DNA testing. And when they lose interest, we lose out on the paper trail information they might add to our mix.

Bottom line: We need to educate our friends and our families, our DNA cousins, to the limits of what these percentages can show — and to show them all the other things DNA testing really can help with.

Because friends don’t let friends do DNA testing only to get these percentages.


SOURCES

  1. See e.g. Judy G. Russell, “Admixture: not soup yet,” The Legal Genealogist, posted 18 May 2014 (http://www.legalgenealogist.com/blog : accessed 22 Feb 2015).
  2. Grand nephew if you prefer.
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