You open your article on demography and genetics with the claim that “one of the biggest paradoxes in human biology is that people have fewer children as societies grow richer” (“Kissing Cousins, Missing Children,” February 9, 2008). Come again? To tell you the truth, I had to read this sentence several times because it struck me as so off the mark that I thought I must have misread it. To begin with, nomadic hunter-gatherers had fewer children than their sedentary agricultural successors. One reason for a larger number of children that came with the agricultural revolution was greater abundance of food, but another was greater mortality due to greater incidence of endemic diseases in larger and denser populations. More important, elites had fewer children than others even in agricultural societies. The unsurprising reason for this was the preservation of wealth and power within the family. No paradoxes here. And no trace of human biology, either.