Post Reproductive Life Stage

Women unlike other female primates usually outlive their fertility. While fertility ends at similar ages in all female hominids, great apes rarely survive through their forties. Girls, on the other hand, if they do not die before adulthood, usually live through menopause and beyond. This post-menopausal survival is often termed “post reproductive,” making it an evolutionary riddle. How could selection maintain the functioning of physiological systems if variation in performance had no effect on the number of gene copies in future gene pools? In the middle of the twentieth century this riddle was solved with the recognition that the number of future gene copies depends not just on fertility, but on the survival and success of kin sharing copies of those genes. Subsequently, age-specific mortality patterns in both human hunter-gatherer and great ape populations became better characterized. Documentation of the distinctively longer life spans of humans and the economic importance of women past their childbearing years in subsidizing their daughters’ fertility and their grandchildren’s survival has revealed the importance of this life stage in our distinctively human pattern of cooperative breeding.