Putting the Gene Back in Genealogy

When I told my grandfather about our family's results, I asked if he was disappointed to see no trace of African blood. "No," he said, after sitting silently for a long moment. "It
doesn't make me feel anything special, except that I think there was something wrong with that test."

Was there? "She might have been within the range for the test to pick her up," said Mark Shriver, a consultant for DNA Print and assistant professor of anthropology at Penn State, when I asked him how to interpret the results in light of family lore. "Unless she was a light-skinned African. If she was 100 percent African, that would give your grandfather 6.25 percent; if she was light-skinned, that would decrease his number, but he should still have some. It could be that by chance he didn't inherit her African genes, or maybe she's right outside the detectable range."

Or maybe it's a result of limitations in DNA Print's database. "It's possible to learn something about a person's ancestry with autosomal (nuclear) DNA testing," says Noah Rosenberg, a genetic anthropologist at the University of Southern California. "But you have to be very careful. When they say you're 90 percent European and 10 percent Native American -- that's based on samples they collected from people they decided were representative of Europeans and Native Americans. So really what they've told you isn't what ethnicity you are, but how similar you are to the people in that database." If you change the database, you change the results.

DNA Print built its database from 3,000 SNPs. To ensure purity, they didn't use, say, African-Americans, they used native Africans. But, as Mark Shriver says, there's no way to know for sure who's purely African, European or anything else. "You just try to collect the best samples you can," he says. "It is important to realize that we're not measuring anything essential or absolute about the DNA, we're just referencing it to samples that we know more about."

Most of the geneticists I talked with look forward to the day when there is a worldwide DNA database large enough
and diverse enough to legitimately represent different populations. With such a database, they say, providing precisely accurate information about a person's genetic heritage could be possible. Meanwhile, geneticists make do with various public and private databases; the largest -- an NIH database called dbSNP -- contains four million SNPs. The frequencies of some of them are being measured in populations including East Asian and African-Amercan. But scientists involved emphasize that this isn't intended for personal genealogic testing. "We're collecting this data for medical research," says Harvard geneticist David Altshuler. "What these companies are doing is, in my opinion, an unfortunate consequence of that research." The NIH's dbSNP may someday be a valuable resource for, say, studying population migration on a global scale. But it's nowhere near the size required for applying it to an individual.

"In no way am I saying their product is totally bogus," says Ranajit Chakraborty, a population geneticist at the
University of Cincinnati. "It has some scientific basis." If a person has many ancestry-informative markers that are common to Africa, there's a good chance that person is of African descent to some degree. But even that can't be stated with absolute conviction. "You can say one group has a certain population-
specific variation, but it doesn't mean that mutation is not found in other
populations as well," Chakraborty says. "So you cannot be very precise. If I take your DNA and type it and say you're 100 percent European, that does not mean you don't have African origin genes somewhere in your genome."

Ultimately, every expert I talked to -- even those affiliated with the ancestral DNA companies -- agreed that no DNA test can make definitive statements about ancestry (such as "Rebecca Skloot is 90 percent European and 10 percent Native American"). But nuclear DNA testing can tell me I have some genes that are more likely to be Native American than something else. That information may be worth a few hundred dollars to some people, because it just might help scale a few brick walls. "Beliefs tend to drive traditional genealogy research," says DNA Print's founder, Tony Frudakis. "If you think your ancestors were European, you'll only look in European archives. These tests can open new paths to follow in genealogy research."

But one thing is certain: To date, no ancestry test can rule out part of a person's history simply because it doesn't detect it. When I told Noah Rosenberg that my DNA tests found no evidence of Elenor Hickenbottom, he chuckled. "Let's put it this way," he said. "I wouldn't discount your family story just yet."

Contributing editor Rebecca Skloot's first book, The Immortal Life of Henrietta Lacks, is forthcoming from Crown.