Using 19th-century locks of hair that appeared serendipitously, Edward Ball embarked on an investigation of his family history through its DNA. He reveals the surprising results, and the wonders and flaws of DNA testing, in The Genetic Strand.

How much did your experience writing your National Book Award—winning Slaves in the Family influence your decision to have the DNA in your ancestors’ hair analyzed?

I was reluctant to start, because I had already written about my father’s family in such detail in Slaves. The reality was that I had a very unusual resource in this genetic raw material. I realized it was something other people would not have: body parts from their ancestors. That fact persuaded me to go ahead.

What did you hope to learn from the DNA tests?

I was expecting, initially, that I would be able to learn more about the medical history of these long-dead people, but that was because I was largely unaware of the limits of the science. When I realized that, I was a little disappointed, because I thought that the remaining questions—geographic origins and racial identity—would be sewn up right away and I would find nothing surprising. Then I learned about the alleged presence of Native American and West African genetic markers in our family genome. Once I got those results, I was really interested to find out more.

How did the alleged unexpected markers change your view of your family history?

I wasn’t able to make sense of it at first. It was pretty startling because I come from Southern families that have a real emotional investment in their white heritage. I think most Americans assume that they have a monocultural or monohistorical inheritance. They’ll say, “I’m Italian-American,” and they might have three great-grandparents that were Sicilian immigrants, and then they might also have a Mexican-American great-grandmother and 20 other strands of cultural inheritance that they’re not even aware of.

What do you think now about the reliability of DNA?

There’s this sort of mass opinion that’s come about in the last 20 years that DNA is a Rosetta Stone, that it discloses everything about biological identity. I’m pretty convinced there are a lot of flawed data, flawed databases and mishandled evidence, and a lot of mistakes made, that are not being talked about. You do hear, often, because the press loves the story, about the exonerated capital criminal, but you don’t hear about people who may be convicted based on flawed DNA evidence, which is handled like sacred text. I think that’s a scandalous story that’s not being told.