Darwin’s fundamental insight as a biologist was that, among members of a species, what is important is not the similarities but the differences. If human beings were identical, a single change in the environment could wipe out the race. Similarity, ultimately, is death. So why do Darwin’s followers in evolutionary psychology want to make what people have most in common into a social good? What the new sciences of human nature seem to show, for all their investigations down there among the genes and the neural networks, is that “human nature” is as much an abstraction as “God” or “the universal law.” It is a magic wand that people wave over the practices they approve of. If that makes them feel better, who can complain? Human nature is never the reason for their approval, though. It would be nice if we could justify our choices by pointing silently to our genes. But we can’t. Our genes, unfortunately, are even stupider than we are.