Admixture: not soup yet

And maybe never

The Legal Genealogist wants everyone who’s ever taken a DNA test that provides a set of ethnicity or admixture estimate percentages to repeat after me:

“It’s not soup yet.”1

And it may never be.

So… while I was on the road (and coping with the now-dry-but-once-flooded basement), Family Tree DNA released its new myOrigins ethnicity estimates, a major upgrade from the old Population Finder.

myorigins2It’s a major step forward in our quest to gain information about our distant ancestors — where they lived, where they came from. It’s as good as it comes given the limits of science. It applies the very best of a set of statistical algorithms to what science knows to come up with a formula that tells us what it can about our origins.

And the very best of what it can tell us is still a guess.

Now you may be sitting there thinking, “but they don’t teach this in law school. How can she know?”

I know because I’ve spent a fortune testing relatives who’ve been kind enough to let me manage their results. And I can see what happens when, for example, you apply the very best of a set of statistical algorithms to what science knows to come up with a formula — and then apply that formula to people whose results should be pretty much identical.

People like my mother’s full blood siblings.

Four of them have tested. They all share the same mother, same father, so same grandparents and great grandparents on back into the mists of time. Their DNA establishes that fact beyond any question. No non-paternal events here, no undocumented adoptions.

So if all four have exactly the same parents, and grandparents, and great grandparents, and on back through the generations, they ought to have the same genetic admixture, right? Ethnically, looking back at their heritage 500 or 1,000 or 10,000 years ago, they can’t be different.

Except they are, at least according to this very best of statistical algorithms. Take a look at the chart below:

myorigins1

So… the population group labeled European Northlands “centers on the people of Scandinavia.”2 Does this family have any Scandinavian ancestry? Three of the four show traces, the fourth shows none at all.

Well, then, what about the North Circumpolar group — a group that “began around the arctic as hunter-gatherer peoples … (and) stretches from Lappland east to Greenland”? Three of the four show traces of that, the fourth shows none at all.

What about the North Mediterranean Basin population? A “distinct European cluster… situated in the southwest of Europe from Spain to Greece.”3 Three of the four show traces of this group, the fourth shows none at all.

We might be tempted to say yes to all three of those cases, because three out of four — 75% — of the siblings tested do show traces.

But what about the Trans-Ural Peneplain? The “dominant group between the tundra and the steppe in Eurasia’s northwest … from the area where the North European Coastal Plain joins the forests of Central Siberia.”4 One has it, three don’t. Eastern Afroasiatic? A group that “developed in the Persian Gulf north toward the Zagros Mountains.”5 One has it, three don’t.

How can this be?

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.

These limitations are true of all of the testing companies, not just Family Tree DNA. 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.

It isn’t soup yet.

And because we aren’t about to go digging up those old bones, it may never be soup.

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. For those too young to remember the reference, the Lipton Soup Company had a string of ads in the late 1960s and early 1970s. The mother in the ad would begin preparing Lipton soup, a child would ask, over and over, “is it soup yet?” and the mother would answer “not yet” over and over until finally she’d say, “It’s soup!” So “not soup yet” means “not finished” or “not ready.”
  2. Population Clusters in myOrigins,” Family Tree DNA Learning Center (https://www.familytreedna.com/learn : accessed 17 May 2014).
  3. Ibid.
  4. Ibid.
  5. Ibid.
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16 Responses to Admixture: not soup yet

  1. Tim Campbell says:

    Thanks, Judy! I too have tested with Family Tree DNA and I too was amused when I saw myOrigins. The 95% European didn’t change (didn’t surprise me since I’m so white I’m OMG!) but the other 5% skipped a whole continent.

    I did a statistical analysis of my own and realized that Family Tree DNA only has a fraction of 1% of the world population to compare results (same with every other testing company). Genetic DNA isn’t there yet and won’t be until a few million more people get tested.

    I guess I better get out and promote DNA testing.

    • Judy G. Russell says:

      If I can offer a minor caveat… Genetic DNA is there. It’s just this one little part of it, the admixture part, that isn’t — and may never be there in the kind of detail we all want. (I don’t know about you, but forget just telling me what country my DNA comes from — I want every last jot and tittle of my DNA to have a name tag!) We absolutely can — and do — use DNA for all kinds of research questions right now. But answering the question of exactly where in the world our ancestors came from in more detail than the broad continental basis? Not now, maybe never.

  2. Peggy says:

    If one of the siblings had an estimate of greater than 25% of one of the reference populations and each of the other siblings did not at least have a trace of that same reference population then I think the results would be suspect. But as the difference between the siblings is all in those estimates of reference populations below 10%, it really just looks like the random shuffling of the deck that is DNA recombination. But hey, it’s been a long time since college statistics so perhaps someone more up-to-speed on statistics could comment?

    • Judy G. Russell says:

      I’m not a statistician, and don’t play one even in makebelieve life! — but there’s an awfully wide gap to my way of thinking between 69% European coastal plain and 39%!

      • Drew Smith says:

        For my ethnicity estimates on AncestryDNA, my Great Britain percentage is given as 30%, with a range of 0%-56%. The 30% represents the *average* of each of 40 different segments tested for a Great Britain ethnicity (apparently at least one of my segments showed no Great Britain ancestry, and at least one showed 56%).

        I have no idea how many segments Family Tree DNA tests for, but if they use a similar procedure, it would probably be more interesting to see what *range* they predict for each geographic area, and then to see if the ranges overlap between siblings.

        • Judy G. Russell says:

          I would love to see how each segment tests out, Drew! That’s a piece of information that might actually be useful for genealogy!

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  4. Jay says:

    I’m still new to DNA testing, but I’m not impressed with FTDNA’s latest ‘myorigins’. I am a multiracial person and know most of my family history, (African, Native,-both of these are recent, G-G grandparents were African,- East European, French, Swedish, Irish, Scottish, East Asian, and West Asian),and FTDNA’s results didn’t pick up on anything but the Swedish and Irish, (aka European Coastal and European Northlands. I’ve tested with other companies and they showed some of the other racial components.

  5. Robert Hobdell says:

    What you say was pretty clear to me after reading Ancestry.com’s explanation of how their DNA Ethnicity Estimate is generated. The problem is you do not get to access this information before you buy the DNA test (as far as I know). So thanks very much for enlightening potential customers about this. In my case the Ethnicity Estimate did not show me anything I did not already have a good idea of. My only surprise is I’m more Irish than expected. For those who are truly clueless about their origins an Ethnicity Estimate may point where to go looking. I think for most folks it is a waste of time.

    • Judy G. Russell says:

      I can’t stress enough that ONLY the ethnicity part is at issue here. There is so much we can all learn from autosomal testing — it’s just that these percentages aren’t really a good reason to test in the first place. So anyone interesting in genealogy SHOULD do autosomal testing, but for genealogy — for finding cousins and getting access to those parts of our family story that only those cousins have. And if we ever get decent percentage to go along with the autosomal cousins we find, well, that’ll be a net plus.

  6. Barbara says:

    I am new to the DNA testing. Just received my results and have been avidly reading and educating. I think what needs to be pointed out when testing siblings is the randomness of that 50% you receive from each parent. Just because you share the same parents does not mean you inherited the same genes. Each of us is a unique genetic combination. I am looking forward to seeing my brother’s results. We look nothing alike so I don’t need a DNA test to tell me we inherited different versions of those genes. Comparing our DNA results using the admixture testing will be very interesting and I will not be surprised if our percentages are way off.

    • Judy G. Russell says:

      Your admixture actually should be fairly close… but it’ll be interesting to see if it is!

  7. Lynn David says:

    AncestryDNA had it’s Scandanavian ethnicity so ramped up that people got mad at them. So they came up with v2 which still has its problems. Some I have pointed out here:

    http://ancestryforums.custhelp.com/posts/cd43442e65

    Anyone should be taking these estimates with a teaspoon of salt.

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