Our research on human life history strategies focuses on two areas: the adaptive function of human juvenility, and the importance of inter (and intra)-generational cooperative social networks for understanding reproductive decisions. 

Juvenility.   Theoretical models suggest that the difference between human and nonhuman primate life history patterns may be due to a reliance on complex foraging strategies requiring extensive learning. These models predict that children should reach adult levels of efficiency faster when foraging is cognitively simple. We test this prediction with data on Meriam and Martu children’s foraging.  Meriam children reach adult efficiency more quickly in fishing as compared to shellfish collecting, probably due to the latter’s strong size and strength constraints. Martu children in the Western Desert show similar patterns: children prefer to forage for rock goanna, which involves heavy digging, but which is concentrated in patches (thus reducing travel costs), while adults prefer sand goanna, larger but widely distributed in sandy inter-dune plains.

Cooperative breeding.  Mothers are increasingly recognized as having significant impacts on their grown children’s fertility. They may do so in two very different ways: through expensive forms of parental investment designed to reduce their grandchildren’s mortality or morbidity, or by continuing to invest in grown daughters, working longer hours to produce more food in order to reduce daughter’s own workload.  Such intergenerational cooperation could play a role in the evolution of menopause, that peculiar phenomenon of living well past the age at which reproduction effectively ceases. We also suggest that task specialization between female kin might also play an important role in women’s social and economic strategies. We use historic group composition data for Martu to show how women maintained access to same-sex kin over the lifespan. Our results show that adult women had more same-sex kin and more closely related kin present than adult men, and retained these links after marriage. Maternal co-residence was more prevalent for married women than for married men and there is evidence that mothers may be strategizing to live with daughters at critical intervals, early in their reproductive careers and when they do not have other close female kin in the group. The maintenance of female kin networks across the lifespan allows for the possibility of cooperative breeding as well as an all-female division of labor.