SEX AND THE BIRTH-RATE - HUMAN BIOLOGY, DEMOGRAPHIC-CHANGE, AND ACCESS TO FERTILITY-REGULATION METHODS

Success, in evolutionary terms, means contributing more surviving offs pring to the next generation than competing individuals of the same sp ecies in the same population. Human conception is a probabilistic even t occurring against a background of frequent, usually infertile sex, w hich helps bond parents together. Humans have an innate drive for sex and for nurturing their children as they arrive, but they have no biol ogical predisposition for a specific number of children. In preliterat e societies, in the absence of artificial means of fertility regulatio n, pregnancies are spaced several years apart by unconscious physiolog ical mechanisms based on breastfeeding. In preliterate and in preindus trial urban societies, socially successful individuals commonly had la rger than average families. Once people have unconstrained access to a range of fertility-regulation options (including safe abortion), fami ly size falls in all groups and in all societies. In such a context, s ocial success tends to be associated with the accumulation of material wealth, rather than with having more children. The argument that deve lopment causes fertility decline is flawed because people cannot make choices about family size without realistic access to fertility-regula tion technologies, and such access is historically recent and remains geographically limited. Where access to fertility regulation is constr ained, the richer and more educated are usually better able than the l ess privileged to surmount the barriers between them and the needed te chnologies. hence the common inverse relationship between income and f amily size. Policies derived from this perspective are discussed.