LAUSR

Significance Prominent explanations for postreproductive longevity emphasize the myriad ways in which older adults help descendants in social species. However, standard metrics expressing how natural selection acts with age show declines in tandem with reproduction, rendering postreproductive life vulnerable to harmful mutations. Here, we develop a framework for estimating three fitness metrics to characterize the “force of selection” in social species with pooled energy budgets. We show that intergenerational transfers of food and information in the complex, high-skill foraging niche typical of hunter-gatherers can select for longer lifespan via inclusive fitness benefits. Our findings support the theory that postreproductive life in some mammals coevolved with multigenerational cooperation in a complex foraging niche and help explain selection against late-acting deleterious alleles.