WASHINGTON: Oprah is a Zulu. Never mind that she was born and raised in Mississippi and her great grandparents hailed from no further away than Georgia and North Carolina, Ms Winfrey, the queen of the televised confessional, is not just suggesting her lineage might stretch back thousands of years to a specific African tribe. She is asserting it as a definitive fact. “I always wondered what it would be like if it turned out I am a South African. I feel so at home here ... Do you know that I actually am one?” she told an audience of 3,200 in Johannesburg last year. “I went in search of my roots and had my DNA tested, and I am a Zulu.”

This month in the US, Oprah has been joined by eight other African-American luminaries, including Quincy Jones and Whoopi Goldberg, in tracing their genealogy. Thirty years after Alex Haley famously traced the oral history passed down through his family back to Gambia to find his African ancestor, Kunta Kinte, who had been sold into slavery these celebrities will undertake a similar journey alongside Harvard professor Henry Louis Gates Jr in a television series called African-American Lives. But unlike Haley’s Roots, few have been able to turn to family historians in search of their genealogical narrative.

So when the stories stop and the paper trail of slaves bought and sold runs out, the participants have turned to genetic science to trace their kin. But while these journeys into the past are essentially personal, they raise broader issues about racial authenticity and the genetic basis for racial categorizations. Furthermore, it addresses the fundamental issue of whether any of us can, ultimately, really say where we come from — and what use it would do us even if we could.

Over the past few years laboratories have begun to amass a database of DNA samples from around the world, including parts of West Africa, the area from which most slaves were caught, sold and shipped to the Americas.

The technology aims either to trace a person’s lineage through their genes or compile a statistical breakdown, by geographical region, of their genetic makeup. Alondra Nelson, an assistant professor of sociology and African-American studies at Yale, says results “could stretch from several thousand years to tens of thousands of years in a person’s ancestry”.

Mark Shriver, an assistant professor of anthropology and genetics at Penn State university, conducts geographical genetic tests on his students among others. He describes himself as white but his own tests reveal that his DNA is 86 per cent white but also 11 per cent west African and 3 per cent indigenous American. “For most people it is consistent with what they thought,” he says. “How the west African DNA got into my family line was never explained to me.”

Another method of testing follows the genes back through gender lines. One, the patrilineal, follows the Y chromosome through your father, your father’s father, your father’s father’s father and so on. The other, the mitochondrial, follows DNA through your maternal line — or your mother’s mother, your mother’s mother’s mother and so on.

“It’s basically a matchmaking game,” Megan Smolenyak, an expert in family history research, told the New York Daily News. “I like to warn folks: be sure you can deal with the results ... Some people don’t like what they find.”

The science, now commercially available, has become something of a boom industry. Growing numbers of relatively wealthy African-Americans have been buying up test kits that can cost up to $350 (£200) a throw. While other Americans could travel to towns in Ireland, Italy or Germany in search of genealogical sustenance, slavery deprived African-Americans of a clear and precise geographical bond with their own ancestry. As Gates puts it: “There is no Ellis Island for the descendants of the slave trade.” Moreover, since slave-owners changed people’s names, regularly split up families and banned reading and writing, the usual methods of keeping family histories have not been available to African-Americans until relatively recently.

This new science, then, seemed to offer a means of telling a story that had been denied and hidden. Even as DNA evidence was freeing many — mostly black — prisoners from death row it was also unlocking historical secrets. For example, historians had insisted for 150 years that America’s third president, Thomas Jefferson, could not have fathered children by his slave mistress Sally Hemmings. Many African-Americans claimed otherwise, however, and in 1998 scientists followed the Y chromosome DNA in Jefferson’s family line to establish a definitive link with the Hemmings family. Almost 200 years after Jefferson had cryptically parried accusations of the affair with the words “the man who fears no truth has nothing to fear from lies”, science had exposed the facts that a mixture of prejudice and politics had kept hidden.

In reality, however, the truths this science reveals are no less selective than those you will hear from a politician. Two years ago I swabbed my cheek with something that felt like a cotton bud and sent it off to a Washington-based organization called African Ancestry. Several weeks later it sent me a letter telling me that the “Y chromosome DNA sequence that we determined from your sample matches with the Hausa people in Nigeria ... This result means that you have inherited through your father a segment of DNA that was passed on consistently from father to son to you. This segment of DNA is presently found in Africa in Nigeria.”

They also sent me a map showing me where Nigeria is and a “certificate of ancestry” declaring that I “share paternal genetic ancestry with the Hausa people in Nigeria”. It went on, “You can display it with pride among other important family documents.”

Elsewhere in the letter, however, came information that would seem to minimize the entire enterprise if not negate it altogether. “The Y chromosome may represent less than 1 per cent of your entire genetic makeup” it said. That is to say that I had possibly been awarded an ancestry courtesy of a fraction of my DNA.

Herein lies one of the central problems with tracing ones roots through DNA. Science can only tell you so much. Stop the genealogical wheel at an inconvenient moment and some of the world’s greatest black icons could be rendered not African, but European.

According to Shriver, Gates — the most prominent black academic in the country — has DNA that is 50 per cent European and 50 per cent West African. Both his matrilineal and paternal lines came back to Europe. “I’ve spoken with African Americans who have tried four or five different genetic genealogy companies because they weren’t satisfied with the results,” says Nelson. “They received different results each time and kept going until they got a result they were happy with.”

“There are some people who are black who may have only 10 per cent African ancestry,” says Shriver. —Dawn/The Guardian News Service