Department of Anthropology
Are humans cooperative breeders? A review of the empirical evidence
Monday, November 22, 2010
Lecture Hall 2, 5:00 PM
Children pose a problem. An unusually extended period of childhood dependency and relatively short inter-birth intervals mean that human mothers have to care for several dependent children simultaneously. Most evolutionary anthropologists now agree that this is too much of an energetic burden for mothers to manage alone. It has been suggested instead that humans are cooperative breeders: mothers must enlist help from other relatives to share the costs of raising children. If this is the case, then there should be empirical evidence which documents the beneficial effects of kin on reproductive success. Here I review all studies which have investigated the impact of kin on two components of reproductive success: child survival and female fertility rates (37 and 39 studies, respectively). It is clear from this review that family matters: the presence of relatives improves child survival, across a wide geographical and historical range of populations. Which relatives matter differs somewhat between populations, but grandmothers, particularly maternal grandmothers, and elder siblings of the child seem to be particularly beneficial. Fathers and grandfathers are less important. Similarly, family matters for female fertility. Overall this review of the empirical evidence suggests that women are influenced by, and reliant on, their kin during their reproductive lives, thus providing support for the hypothesis that humans are cooperative breeders.
My research interests lie in human behavioural ecology, particularly focused on two main areas: investigating the impact of kin on reproductive outcomes, and examining relationships between health and reproduction. Most of this research has been on high fertility populations in the developing world, specifically sub-Saharan Africa, but I also have interests in the demographic transition and low fertility regimes. My training is in Zoology (BSc, University of Nottingham) and Biological Anthropology (MSc and PhD, University College London), but my research on demography resulted in a position at the London School of Economics teaching Population Studies. I have just returned to Anthropology, however, having recently taken up a Readership in Evolutionary Anthropology at the University of Durham. I am also a co-founder and Vice President of the European Human Behaviour and Evolution Society.