Energetic demand of multiple dependents and the evolution of slow human growth.

This study investigates the consequences of the human foraging niche and multiple dependent offspring on the optimal growth trajectory of humans. We test the hypothesis that the human pattern of slow human growth between age at weaning and puberty helps defer the compound energetic demand on parents with multiple dependents, by using growth and demographic data from two foraging societies, the Ache of eastern Paraguay and the Dobe Ju/'hoansi of Botswana and Namibia. We run simulations of observed and potential growth trajectories among sub-adults and their consequent energetic demands on parents given profiles of fertility, mortality, consumption and production. We find that either sub-adult production or food subsidies from other people must substantially increase in order to compensate for the dramatic increase in energetic demand on parents if offspring were to grow faster at younger ages. Our conclusion is that slow human growth followed by a rapid adolescent growth spurt may have facilitated rising human fertility rates and greater investments in neural capital.