Determinants of Post-Reproductive Lifespan & Life History: A Description of a Novel Proxy of Reproductive Stress, Offspring Ratio

Abstract

Why does reproduction in many female organisms cease well before the end of life? Previous work has found that this post-reproductive life is a feature of many species and is not confined to humans enjoying the benefits of modern medicine. In fact, recent research suggests that reproductive aging can be uncoupled from somatic aging through genetic mutation. Reproductive aging, then, can react to a different set of inputs than somatic aging, presumably including the stress of childbirth and other factors. We report the construction of a proxy for the stress of childbirth from the ratio of the size or weight of offspring to that of the mother. Across a variety of taxa, from sea urchins to humans, this proxy exhibits a statistically significant correlation with the length of post-reproductive life and with the length of other periods, including gestation, maturation to adulthood (childhood), and reproductive life. These relationships, along with experimental data, suggest a conserved molecular, regulatory, and genetic mechanism relating maternal stress to different life history parameters.