In 1977, Alondra Nelson remembers lying stomach-down, head-in-hands, in front of the television, watching Alex Haley’s miniseries Roots with her parents. “I knew that something special was happening because my parents didn’t let us watch TV in the evenings, and here, they were letting us watch eight nights in a row,” she told a crowd at the Aspen Ideas Festival, which is co-hosted by the Aspen Institute and The Atlantic. “They wanted us to see it for its historic nature.”

The miniseries, which traced Haley’s genealogy back to the Gambia, spurred many African Americans to start tracing their own ancestries. And it inspired Nelson’s own interest in genealogy and the social consequences of learning about one’s roots. Now, as the dean of social science at Columbia University, Nelson has spent more than a decade studying what she describes as a “new groundswell of root-seeking”—one propelled by genetic testing.

Today, there are dozens of companies that will sequence segments of a customer’s DNA and tell them about their ancestry. When Nelson asked the audience how many had made use of such services, at least a dozen people raised their hands. But in 2002, the industry was a nascent one. To find its early customers, Nelson had to go to old-fashioned genealogy clubs and societies.

The history of genetics as a field is steeped in eugenics and scientific racism. And yet, Nelson says that for many African Americans, DNA testing held a special appeal because many of the traditional methods of genealogy had been complicated by the history of slavery. Records disappeared. Names changed. People were trafficked across state lines. Stories were verboten because they were too traumatic. Ancestry testing offered a way of circumventing these obstacles, and airing stories that might never otherwise have come to light. “It’s an interesting story about race and genetics,” Nelson says. “When we talk about African Americans in science, it’s often a story of skepticism and distrust. But this ancestry-testing story is one of pioneering early adopters who are willing to do something different.

One such pioneer was Rick Kittles, a geneticist and cancer researcher who founded a company called African Ancestry Inc. His service provided only broad inferences about where people came from, but for many customers, that was enough. “It definitely wasn’t perfect, but many people said that if it’s a choice between no information or an inference that might be slightly off, I’ll take the inference,” Nelson says.

As tests became more precise, those inferences often proved to be unexpectedly moving. Nelson once met a group of African Americans whose DNA suggested that they had Sierra Leonean ancestry. They met for a ceremony of remembrance on the Ashley River in South Carolina, at a ferry landing where slaves were disembarked from ships and auctioned off. The actor Isaiah Washington was there. A man cast soil and stones from Sierra Leone into the river and said a prayer.

“We talk about the history of slavery in this country and it feels so abstract. But genetic ancestry testing can make it very personal,” she says. “The ceremony allowed for a social practice of healing, where people didn’t just have to sit with the knowledge. Many of the folks I talked to tell very moving stories about new relationships they began in their communities with their genetic test results.”

Nelson expands on this theme in her recent book, The Social Life of DNA. In it, she argues that DNA is more than a molecule that defines our identity; it also takes a social life beyond its influence within individual bodies. The communities that can arise from ancestry testing are a far cry from the cutesy images often used to sell ancestry tests, in which bemused people swap lederhosen for tartan. “This test was not just about identity in a narcissistic way, but about people trying to reconcile the history of slavery, and scaling up from their ancestry test to what it means for the history of the U.S.,” says Nelson.

When Nelson first looked at ancestry tests, they were mainly of interest to the 50-plus crowd. But they’re now capturing the interest of a younger demographic who are drawn to the quantified-self movement, and the power of dramatically revealing where you came from, reality TV-style. Nelson knows that power first-hand. “I didn’t want to do the test, but I thought if I was going to do it, it would be with a big reveal,” she says.

It happened in an Atlanta ballroom, with Rick Kittles and Isaiah Washington MCing. At the event, Martin Luther King III learned his ancestry on his mother’s side traced back to Africa, while his father’s line traced to Scotland and Ireland. He told a story about how we’re all related in the end, and spoke about his desire to go to Europe. Marcus Garvey Jr.’s son heard similar results—a mother’s line that descended from Africa and a father’s line that came from the Iberian Peninsula. He told a story that highlighted the horrors of slavery. “It was an example about how these results, even when they’re very similar, get taken up into these stories that are important to us,” says Nelson.

She learned that her mitochondrial DNA (which passes down the female line) traced back to the Bamileke people of Cameroon—a fact that delighted her mother. “She couldn’t wait to tell everyone,” Nelson says. “And then soon after, she developed a close relationship with a woman from Cameroon, whose family would spend holidays with us. Her son had grandparents’ day at school, and since his grandparents are in Cameroon, he invited my mother—the DNA Cameroonian—to be his grandparent for the day.”