Constraints on Consanguinity As A Function of Fertility

Even in traditional societies where marriage among relatives is wide-spread, fertility is declining. So is the availability of eligible cousins. The custom of cousin marriage has so far persisted in the face of modernization, but cannot persist – at present levels and in present form – in the face of the demographic transition. We show through simulation, with comprehensive sensitivity analyses with respect to model specification, that current and projected fertility levels in Middle Eastern countries create challenging constraints on the custom once today's birth cohorts reach marriageable age. This is true both from the individual and the aggregate perspective. Either consanguinity prevalence will diminish, or the institution will be forced to adapt, at the expense of other social preferences (such as for an older groom wedding a younger bride). Accordingly, fertility decline affects prospects for social change not only through its well-known consequences for mothers, but also through shaping marriage conditions for the next generation.