In her early 20s, Christine Kenneally discovered something about her Australian forebears that upended her sense of identity and family history. In her new book, The Invisible History of the Human Race: How DNA and History Shape Our Identities and Our Futures, she explores the power of DNA to reveal secrets in our past and predict our future...

One of the most fascinating things in your book was the idea that the legacy of historical events like slavery or the Black Death can shape our ability to trust people—and the success of a society. Tell us about the work of Nathan Nunn.

Nathan Nunn is a pioneer among a group of economists who are using big data to look at the impact of historical events on attitudes of today. With another economist, Leonard Wantchekon, he conducted this incredible study whereby they looked at levels of interpersonal trust in Africa today.

They asked if slavery had any kind of impact. What they found was that there was a correlation between regions where more slaves were taken and lower levels of trust today.

Wantchekon is a Princeton economist now, but he grew up in Benin, West Africa, one of the main slave exporting centers. And when the results of their research became known in Benin, there was a huge response. Many people got in touch with him and gave him these heartfelt acknowledgments that he'd identified something that was real—and was shaping their lives today.

We think of a country like the U.S. as a melting pot where people from different cultures blend together by adopting the values of their new homeland. But your research shows that immigrants often reproduce old values even their ancestors have left behind.

Absolutely. The myth of American independence as complete abandonment of the Old World is not true. People very much bring the Old World with them. One study looked at how many children women from different cultures were likely to have.

And what they discovered was that they're influenced by the numbers of children their grandparents had, by the choices their grandparents made, even if they've never met those grandparents or been back to the Old World.

Obviously, their grandparents' children, their own parents, bring those values with them, and it influences their life choices. I love that, because we think of these choices as so personal and so completely independent. They're choices you make by yourself or with your partner. But no matter what you tell yourself, what your grandparents were up to also seems to affect you too.

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