Study probes genetic ancestry tests
America might be a melting pot, but that does not stop ancestry from bubbling up in the national consciousness. Identity springs from it, art dwells on it and society ponders it. The dawning of modern genetics has only further whetted our appetite for such knowledge, inspiring 460,000 people in the past six years to spend $100 to $900 on commercial genetic ancestry tests.
But according to a study published in the Oct. 19 issue of Science, the results of such tests should be taken with a grain of salt.
The article, titled “The Science and Business of Genetic Ancestry Testing,” was co-written by Kimberly TallBear of ASU’s department of American Indian studies. It cautions that the tests are fraught with assumptions and limitations – and, therefore, probably are not as enlightening as people would like them to be.
“The problems with the tests are both technical and social, and those two things are entangled,” TallBear says. “So we have these oversimplifications of human social and ethnic history that lead to inadequate scientific assumptions and interpretations of genetic data.”
The basic idea behind genetic ancestry testing is to compare telltale snippets of the buyer’s DNA to a geographic catalog of equivalent telltale snippets from persons around the world. Most tests scrutinize mitochondrial DNA inherited from the mother, or Y-chromosome DNA inherited from the father. The tests check less than 1 percent of the subject’s genetic code and offer clues regarding only one ancestor per generation.
A third type of test, AncestrybyDNA, offered by the company DNAPrint, uses multiple markers inherited from both parents in an attempt to get at a better overall picture – but, according to TallBear, such markers “are not definitive indicators of ethnic ancestry.”
The bottom line is that no genetic ancestry test is free of pitfalls. None can pinpoint with certainty where ancestors lived or what ethnic identity they held. All of them can miss potential matches or report false positives or false negatives. Moreover, genetic ancestry tests provide results that often are open to multiple interpretations.
Given what the authors call the “profound social, political and economic consequences” of race, the article recommends that the American Society of Human Genetics and other genetic and anthropological associations develop policy statements that clarify the limitations and potential dangers of genetic ancestry testing.
“It’s a form of peer review,” TallBear says. “Scientific pronouncements carry tremendous weight in the United States. If the science has some problems – and this science does – the people who live governed by science have a right to know about it.”
Nick Gerbis, firstname.lastname@example.org