Doug Jackson has always wanted to know more about his family history, but that longing grew acute when his 6-year-old son was asked to wear a costume or flag from an ancestor's country for a school "cultural day."

"The other kids had flags from Ireland, England, and many of the countries in South America," said Jackson, co-founder of Shared Vision, an Atlanta-based marketing firm. "The African-American kids were relegated to the continental level. My son would ask, 'What country am I from?' Of course, I didn't know. Our family history stops in the mid-1800s in North Carolina."

So when Jackson learned about a DNA test that promised to trace his roots back to specific parts of Africa, he was thrilled. He took the test last fall and learned that his forebears were from present-day Sierra Leone, Guinea-Bissau and Mozambique.

Jackson is one of dozens of Atlantans who have used DNA technology in recent years to uncover histories lost in the transatlantic slave trade.

Among the latest to learn their origins: Atlanta Mayor Shirley Franklin, artist Fahamu Pecou, jazz musician Russell Gunn and Louis Sullivan, the former head of the U.S. Department of Health and Human Services. The results of their DNA tests were revealed during an invitation-only "Family Reunion" Tuesday night at a South Fulton conference center.

Franklin learned that her maternal line traces back to Sierra Leone. Afterward, she said she has visited many African countries but not that one.

"Another trip is in order," she said.

Stephanie Hughley, head of the National Black Arts Festival, got the most reaction from the crowd when she was told that her test showed she comes from the Balanta people of Guinea-Bissau. Balanta means "those who resist."

Roberta Flack, India Arie and other celebrities will learn their results later in the 10-day National Black Arts Festival, which takes place in various locations around Atlanta.

Atlanta Falcons defensive end Chauncey Davis said he hoped to inspire others to have their DNA tested. "It's very important to know where you come from," said Davis, who lives in Lawrenceville. He learned Tuesday that his maternal line traces back to Sierra Leone.

African Ancestry Inc., the Washington, D.C., company that conducted the DNA tests, will be offering tests to festivalgoers for $275, reduced from the usual $349. The company takes a DNA sample by swabbing a client's cheek then compares it to results in their database of 25,000 indigenous African lines. Tests of mitochondrial DNA can determine from which part of the world someone's maternal ancestors came 10,000 years ago or more.

In some cases, African Ancestry takes it a step further by pinpointing tribal origins — something that is controversial among geneticists. A study last year in a British peer-reviewed journal found that very few DNA samples from African Americans could be traced to a single African ethnic group.

At best, the test can tell people they hail from a particular area in Africa, said Bruce Jackson, one of the authors of that study. He is a geneticist at the University of Massachusetts in Lowell and director of the nonprofit African-American DNA Roots Project.

Celebrities such as Oprah Winfrey, Whoopi Goldberg and Forrest Whitaker have been public about using DNA testing to fill gaps in their family trees. That publicity has helped create a booming business for African Ancestry, which has been offering tests for about four years.

The notion of recovering lost origins is certainly appealing, but not everyone agrees that it is vitally important to understanding one's identity.

"I don't have anything against DNA testing, but I disagree with the idea that you don't have a history or an identity without it," said Jacqueline Peavy, a business speaker from Atlanta. "I know exactly who I am. I am an amalgamation of many ethnic Africans ... I am a new world African in America."

For Jackson, the marketing executive, the DNA test results have proven to be "a great family project." He is going to share the results with relatives at an upcoming family reunion and is planning to take his son to Mozambique next year.