“It is a few selected genes, not the many neutral ones, that may account for the differences between continental races. Substantial evidence for this idea has now emerged from a genomewide survey by Jonathan Pritchard of the University of Chicago. Devising a test to identify genes under recent selective pressure, he found roughly 200 such genes in Africans, in East Asians, and in Europeans. Each race’s set of selected genes overlapped very little with those of other races, just as would be expected if the populations on each continent had adapted independently to evolutionary pressures.”