A leading genetic expert tackles the nature vs. nurture debate

Robert Plomin is no stranger to controversy. It comes with the territory, he tells me, for someone who has spent over four decades studying the role genetics play in making us who we are.

That question is at the heart of a field of science known as behavioral genetics, or the study of the interplay of genetic and environmental influences on human behaviors. The question of how much of a role genetics play in making us who we are is controversial, not just because no one seems to be able to agree on an answer, but also because figuring out how we become who we are is filled with social, historical, and political minefields.

In the past, the belief that genes exclusively determine who we are has led humanity down some dark paths, including social Darwinism, a belief that people were subject to survival-of-the-fittest laws of nature, which was used by some political theorists to justify laissez-faire capitalism and political conservatism. That, in turn, spawned eugenics, a pseudoscience used by various authoritarian regimes to rationalize inhumane policies like selective breeding, sterilization, and even genocide. It’s sensible, then, that social scientists are hesitant to embrace any line of thinking that, in their minds, might lead history to repeat itself.

Plomin, a psychologist and professor of behavioral genetics at King’s College in London, has little patience for this argument. His research tells him that genes account for about half of the differences between us, and that the rest is mostly attributable to random experiences, not systemic forces like the family you are born in. Accepting that, says Plomin, can free us of the anxieties that come from believing everything we do—as parents, as teachers, as friends and neighbors—can irreparably harm our fellow man. That’s why he wrote his book, Blueprint: How DNA Makes Us Who We Are.

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