The passage: Yes, humans have coevolved with culture and geography. Those of us whose ancestors moved far from the equator are descended only from those among the migrants who developed mutations disrupting their melanin-production genes, so that enough sunlight could get through the outer layers of the skin to turn cholesterol into Vitamin D. It looks as though lactose tolerance has evolved six times in the past 6,000 years. Yes, we wish right now that whatever founder effects produced Tay-Sachs disease had not occurred.
