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DNA testing and reliability

Reader Wilma Bittinger was dismayed when her daughter sent her a link to an article on DNA testing that was published online in 2013.

Visualization Of Wave ParticleOriginally titled “DNA Ancestry Tests Are Meaningless for Your Genealogy Search,” the article in the online Medical Daily begins by suggesting that:

Genealogy tracking has become big business, with many companies charging up to $300 to trace your DNA to specific historical figures or ethnic groups in the distant past by analyzing ancestry tests.

A group of scientists now offers a public warning that these ancestry tests have little scientific backing, and are often so unreliable and inaccurate that they amount to “genetic astrology.”1

“Would love to know what you think of their opinion,” Wilma wrote. “I’m not trying to tie myself to any one specific historic figure but they compare DNA testing at our level to astrology. Say it isn’t so!!!”

It isn’t so.

That wasn’t what the scientists who wrote the piece the article commented on said.

And even the article itself ends up saying it isn’t so.

The scientific piece that Medical Daily commented on was “Sense About Genetic Ancestry Testing,” written by Professors David Balding and Mark Thomas, and Tabitha Innocent, Sense About Science; with assistance from Dr Turi King, Dr Lounès Chikhi, Dr Rosalind Harding, Professor Mark Jobling & Professor Guido Barbujani.2

It should tell you something to see Dr. Turi King in the list of contributors: she was one of the lead scientists who researched the Richard III case recently — using DNA evidence as part of the case that the skeleton found under a Leicester, England, parking lot was the last Plantagenet king.

So let’s begin by seeing just what it is that had the scientists upset.

What they criticized — the specific aspect that they called little more than “genetic astrology” — was the selling of DNA tests that tell you if you’re related to a distant historical figure, or that characterize your results with broad labels like “Viking” or “Zulu” or that tell you that “your ancestors moved to a particular part of the world at a specific time.”

And genetic genealogists are as critical of those advertising techniques as the geneticists themselves are.

The problem with saying you’re related to some distant historical figure is that everybody alive today traces back to the same set of far distant genetic ancestors. As the scientists put it, “If you are told that you are genetically related (share a genetic marker) to someone who lived a long time in the past, it may well be true but is not very meaningful. In reality, we all share the vast majority of our DNA through remote common ancestors.”3 That’s why you don’t find genetic genealogists telling you to add, say, Genghis Khan to your online family tree even if you’re an exact match to his known genetic markers.

As for the labels, the scientists note that “people’s genetics don’t reflect discrete groups. Even strong cultural boundaries, such as between the Germanic and Romance language groups in Europe, do not have very noticeable genetic differences.”4 So pigeon-holing results into broad categories like “Viking” or “Zulu” is patently ridiculous.

And genetic genealogists sing the same song on that issue. The Legal Genealogist has written time and time and time again about the simple reality that the percentages reported in the ethnicity estimates by DNA testing companies are just that: estimates, and nothing more.5 They are, to be blunt, cocktail party conversation starters and not a reason to do DNA testing at all.

As for the migration data, the scientists note two problems: the fact that a particular genetic group is found most commonly in one part of the world today doesn’t mean it wasn’t introduced to that part of the world more recently than we’d expect; and the fact that even if it is more common in one part of the world, you individually may have inherited it from an ancestor from another part of the world altogether.6

Yup. And genetic genealogists won’t tell you to add “North African” to your online family tree just because you and many millions of other people share that genetic marker, either.

So… so far… genetic genealogists and the geneticists are in complete agreement. There are some ways that DNA tests are being sold that are just plain silly when it comes to being useful for genealogy.

Does that mean that all DNA testing for genealogy is “genetic astrology”?

It isn’t so.

That wasn’t what the scientists said.

And even the article itself ends up saying it isn’t so.

There’s a highlighted section of the scientists’ report that reads as follows:

There are some things genetic ancestry tests can tell you quite accurately.

There are credible ways to use the genetic data from mtDNA or Y chromosomes in individual ancestry testing, such as to supplement independent, historical studies of genealogy. If, for example, two men have identified – through historical research, possibly involving surnames – a common male-line ancestor in the sixteenth century, it would be reasonable to use their Y chromosome data to test this. There are some ancestry testing companies that offer this service.

To answer a specific question about individual ancestry with any degree of confidence requires a combination of historical records and genetic information.7

And boy do genetic genealogists ever agree with that: DNA testing only works with traditional paper trail genealogy, not instead of it! As much as we might wish that DNA came with each segment neatly labeled with the name, birthdate and birthplace of each ancestor who passed it down to us, it just doesn’t work that way. Using DNA in genealogical research is hard work; it’s part of our proofs, part of our evidence, and takes a lot of effort to use it right.

But because DNA combined with historical research is such a powerful tool, even the article ended up backpedaling away from its original criticism. Medical Daily changed the title of the article from “DNA Ancestry Tests Are Meaningless for Your Genealogy Search” to “DNA Ancestry Tests Are ‘Meaningless’ for Your Historical Genealogy Search” and it added a note at the bottom of the article:

The original version of this article was entitled “DNA Ancestry Tests Are Meaningless for Your Genealogy Search,” which was inaccurate. The source material does not question the usefulness of DNA testing for questions about immediate biological relations, like paternity tests or adoptees looking for their biological families; its criticism was limited to DNA ancestry tests that claim to answer specific questions about ancestors in the distant past without supporting evidence from historical documents.8

In other words, “To answer a specific question about individual ancestry, you need to supplement your … genetic information with reliable historical records.”9

No argument there.


SOURCES

  1. Ashik Siddique, “DNA Ancestry Tests Are ‘Meaningless’ for Your Historical Genealogy Search,” Medical Daily, posted 7 Mar 2013 (http://www.medicaldaily.com/ : accessed 13 Dec 2014).
  2. David Balding, Mark Thomas and Tabitha Innocent, “Sense About Genetic Ancestry Testing,” Sense About Science (http://www.senseaboutscience.org/ : accessed 13 Dec 2014).
  3. Ibid.
  4. Ibid.
  5. See e.g. Judy G. Russell, “Admixture: not soup yet,” The Legal Genealogist, posted 18 May 2014 (http://www.legalgenealogist.com/blog : accessed 13 Dec 2014). Also, “Playing with percentages,” posted 24 Nov 2013; “Those pesky percentages,” posted 27 Oct 2013; “DNA disappointment,” posted 15 Sep 2013.
  6. Balding, Thomas and Innocent, “Sense About Genetic Ancestry Testing.”
  7. Ibid.
  8. Siddique, “DNA Ancestry Tests Are ‘Meaningless’ for Your Historical Genealogy Search.”
  9. Ibid.
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