Many intellectuals enthusiastically denounce those who argue that genes play some role in cognitive differences between human populations. However, such proposals are perfectly reasonable and are, in fact, consistent with the Darwinian research tradition in which most modern social scientists profess to operate. We argue that population-based cognitive differences are congruent with our best understanding of the world because there are strong reasons to believe that different environments and niches selected for different physical and psychological traits, including general cognitive ability. Like most hereditarians (those who believe it likely that genes contribute to differences in psychological traits among human populations), we do not believe there is decisive evidence about the causes of differences in cognitive ability. But we will argue that a partial genetic hypothesis is most consistent with the Darwinian research tradition.