Relationship between energy acquisition and family composition in hunter-gatherers

Abstract

Although previous research on hunter-gatherers has shown that cooperative care and resource provisioning are important traits of human life history, the specifics of these behaviors and their relationship to energy acquisition were undetermined. We developed a simulation model of energy investment in reproduction and child raising in hunter-gatherer families based on empirical data from previous research on hunter-gatherer energy acquisition, consumption, and annual mortality. The model calculates the number of children that a hunter-gatherer family can support until reaching adulthood. Using this model, we explored the optimum value for a life history trait, the age of first marriage, in families with different marriage types and with assistance from different age/sex groups. The model results showed that grandparenting could increase the number of children in families, but whether this was advantageous to the grandparents depended on their energy acquisition. The simulation results generally aligned with observed values for mean age at first birth, prevalence of grandparenting, and age/sex of helpers in cooperative breeding, implying that such traits are strongly influenced by energetic constraints.