Ruth Mace: University College London Department of Anthropology

A behavioural ecological approach to human birth rates suggests they should vary according to the costs of raising children to adulthood. Demographers and most other social scientists are sceptical of this view, not least because birth rates are generally lowest in the wealthiest countries; most favour arguments based on cultural changes and cultural influences. I will argue that evolutionary arguments based on costs and benefits and on cultural influence are not mutually exclusive and that variation in birth rates both within populations and also across populations can be understood in terms of different levels of parental investment and different constraints on parents. I will draw on data from Kenya, Ethiopia, the Gambia and the UK to illustrate these points.