ABSTRACT

Demographic transitions normally entail two features. First, there is a radical decline in the number of offspring that parents produce, despite overall increases in the availability of resources. Second, rich families reduce their fertility earlier, and often more markedly, than the rest of the population, such that the positive correlations commonly found between wealth and fertility in predemographic populations disappear: censuses from England and Wales in 1911 demonstrate this point. In the first hypothesis, evolutionary anthropologists suggest that, in modern societies, lowered fertility rates are optimal because of the competitive environment in which offspring are raised—a world in which high levels of parental investment are critical to a child's success and costly to the parent. The second hypothesis is that lowered rates of fertility are a consequence of darwinian, but nongenetic, mechanisms of inheritance. The third hypothesis is that low fertility is maladaptive—a by-product of changes in our environment that serves no adaptive function.