For decades, Dalton Conley tried to answer the big social questions—about why groups hold together, about inequality, and more—through the traditional tools of his first field, sociology. He eventually found that those tools could take him only so far. So he went back to school and got another PhD—in biology. Now, in The Social Genome, Conley explains how the new field he has helped to pioneer, sociogenomics, will upend our world. The key is the polygenic index, which allows us to analyse DNA to broadly predict a child’s future—not just their height or their weight, but how they may be expected to fare in school, and much more. He argues that we should no longer think of nature versus nurture but of how our genes need nurture to work and how, in turn, our environments are made partly from the genes of other people. The implications of this new science—for our sense of self, for our social policies—are vast.