Revisiting “Grandmothers and the Evolution of Human Longevity” 2003 AJHB https://doi.org/10.1002/ajhb.10156

Abstract

Compared to our closest living cousins, the great apes, humans can live longer with a distinctive postmenopausal lifespan; our development is slower, yet our babies are weaned earlier. Continued investigation since 2003 shows our grandmother hypothesis is a robust explanation for those differences and many other distinctive human features: When ecological changes in ancient Africa spread profitable foraging targets for ancestral adults that infants and small juveniles couldn't handle, reliable foraging by females near the end of their own fertility could subsidize dependent grandchildren and shorten their daughters' time to next conception. Coevolution of shorter birth intervals with slower aging expanded the pool of older still-fertile males. With more competitors, guarding a mate wins more paternities, linking pair bonds to our mid-life menopause. Mate guarding plus older males' advantage in reputation building explains many aspects of human patriarchy. In addition, final brain size in placental mammals depends on the duration of development. As increasing longevity slowed development and expanded brain size, earlier weaning of still physically helpless ancestral infants prioritized their attention and capacities to engage carers. Resulting socially precocious infancies wire us with lifelong appetites for cooperation.