Out of Africa -- but From Which Tribe?
Thursday, October 19, 2006
When DNA testing was offered as a way to trace black family heritage three years ago, it seemed, at long last, that African Americans whose histories were lost in the transatlantic slave trade had found a way home.
TV talk-show host Oprah Winfrey took a test that linked her to the Kpelle people of what is now Liberia. Composer Quincy Jones was informed that he is a likely descendant of the Mbundu or Kimundu tribe in present-day Angola, and Harvard University professor Henry Louis Gates Jr. was told that his ancestry is Nubian. Each test was conducted by African Ancestry Inc., a Washington firm that claims exclusive rights to the most comprehensive database of DNA sequences from Africans.
African Ancestry executives say this large database makes it possible to pinpoint a person's origin to a specific region and sometimes tribe. "It can be done," said Gina Paige, a co-owner of the company. "We don't always just find one group. We tell the client what we find. We determine our results based on the frequency of matches."
But ever since the tests began in 2003, questions have been raised about their accuracy, specifically whether tracing mitochondrial DNA -- which is passed from the mother's side of the family -- can reliably pinpoint a person's tribal origins.
Those doubts were given a public voice this week with the publication of an article in a British peer review journal. It said a study found that fewer than 10 percent of black Americans whose mitochondrial DNA was identified matched perfectly with a single African ethnic group, and 40 percent had no match.
The authors relied on a study that compared DNA sequences from 170 African Americans with DNA sequences from 3,700 Africans who live below the Sahara. "The finding . . . suggests that few African Americans might be able to trace their . . . lineages to a single ethnic group," the article said.
At best, said the article's co-author, Bert Ely, a professor of biological sciences at the University of South Carolina, the test can give people only a probability that they hail from a specific region on the African continent rather than a specific ethnic group.
"What I think is going on is that a company is choosing a maximum-likelihood approach to pick the best outcome" for black Americans seeking their roots, said Ely, who has his own genetic testing company and is a competitor of African Ancestry. "It's not a valid way to draw a conclusion."
Some researchers, while having qualms with African Ancestry's claims, say DNA testing is useful when combined with other genealogical tracing tools, such as historical records, folklore and archeology. "It's probably true that most of the time you're not going to find an exact match," said Jason Eshelman, a molecular anthropologist, who founded Trace Genetics, another DNA testing company, "but there is other information you can tease out to suggest origin."
The popularity of the African Ancestry test and the debate over its claims demonstrate just how emotionally charged the issue of black Americans' lost history is. The yearning of many African Americans to know more of their origins was evidenced by the huge audience generated by the 1977 TV miniseries "Roots," which told of the author's lineage from the African Kunta Kinte.
But some scientists such as Ely, though sympathetic to the quest of African Americans to discover their antecedents, say probability of hailing from a region should not be confused with certainty of descending from a specific tribe. Officials at African Ancestry counter that when it comes to a history-starved race, probability is a good enough place to start.
"It was hard until now to know where I came from in Africa, and the information that my ancestry test has given me is a tool kit that I can use with courthouse records," said Michael Darden, a spokesman for the company. "Knowing that is better than nothing."