In 2000, Harvard University Prof. Henry Louis Gates sent his DNA to Dr. Rick Kittles, a geneticist at Howard University, to trace his ancestry. Kittles, who has since started a company selling such searches, told Dr. Gates that his maternal lineage could be traced back to Egypt, probably to a member of the Nubian ethnic group.

In 2005, Gates, an African-American Studies scholar, had his DNA tested again and was told by another commercial genealogy service that his maternal lineage didn’t track to Egypt, or even to Africa. Instead, it went back to a European in colonial America, who was later found to be a White indentured servant.

As Kittles now concedes, the second version of Gates’s ancestry turned out to be the right one. But the mistakes made by the burgeoning genetic-ancestry industry have continued prompting Gates to start his own DNA-tracing company, one that he says will be able to take a more refined look at African-American ancestry.

Gates’s new company, African DNA LLC, aims to use historians and anthropologists to explain which of various genetic possibilities prompted by DNA traces is more historically likely. For such a search, the new company charges $189, within the $100 to $300 range that’s typical of the genetic-ancestry industry, which now includes at least 10 companies operating via Web sites. For $888, African DNA, which works with Houston-based Genealogy By Genetics Ltd., will include a family tree as far back as census records allow. For most African-Americans, that is usually 1870, when their last names began to be recorded in post-slavery U.S. records.

“I see myself as doing a service for a field that’s deeply problematic, because of the reluctance of some companies to reveal the complexity of the results,” said Gates, who is director of the W.E.B. Du Bois Institute at Harvard, in an interview, He has pledged to donate some of the money that the company earns to an educational effort to teach African history to schoolchildren through DNA analysis.