Nothing in evolution makes sense except in the light of demography: interdisciplinary perspectives on the family
“God has chosen to give the easy problems to physicists” lamented two social scientists in 1975, referring to the challenges involved in understanding human behaviour. Despite significant progress since then in the study of human behaviour, one hurdle which still impedes progress is the existence of disciplinary boundaries which keep apart researchers studying similar behaviours. While the evolutionary behavioural sciences have a head start in this regard, in that they are already integrating some social and biological sciences, this talk will argue that they could go still further in integrating a greater range of disciplines into their research. This talk will particularly focus on how a better understanding of demography can help improve evolutionary analyses. It will then use the example of a research programme exploring how reproductive behaviour is influenced by the family, to illustrate the usefulness of such an interdisciplinary approach. This programme uses evolutionary theory as its framework, and tests one prediction from the hypothesis that humans are cooperative breeders: that reproductive behaviour will be influenced by the presence of family members. But it draws heavily on the methods of, and previous research from, demography. Cross-cultural data will be used to show that women and men are often sensitive to the presence of family members when making reproductive decisions, but how these influences play out is context-specific. Further, these analyses suggest both cooperative and competitive relationships within the family. Finally, the talk will consider the implications of this cooperative reproductive strategy. An understanding of the human family which incorporates relationships beyond the nuclear family may change our perspective on many topics of interest to evolutionary scientists, including parenting, mate choice, and the development of life history strategy.