Reproduction, senescence and lifespan in humans
Women optimise investment in numbers of grandchildren through decisions on current and future reproduction. It is possible that older women increase their fitness by directing resources to already produced offspring (children and grandchildren) rather than having more. To understand the ecological and genetic basis of reproduction, senescence and lifespan, knowledge is needed on the effects of social and demographic factors, among others. To realise this, the project HUMAN LIFESPAN (Mothers, grandmothers and the evolution of prolonged lifespan in humans) posed and answered five relevant questions. The study used unique demographic data from as many as 15 generations of individuals who lived both before and after the availability of healthcare and modern contraceptives in Finland. The first question considered how reproductive investment affects reproductive and post-reproductive senescence in humans, and the second what proportion of grandchildren is gained in the post-reproductive phase and what factors influence this. The third question pondered whether there is heritable variation in the life-history traits and their senescence rate, and how genetic correlations between them influence evolution. The fourth question explored how patterns of fitness acquisition account for menopause, prolonged post-reproductive lifespan and, ultimately, the age of death in humans. The last question focused on how fitness-maximising traits differ between men and women and how this reflects on their lifespan. HUMAN LIFESPAN has contributed new knowledge on the topic, with findings that can be used for predicting demographic structure in human populations. The results also advance a better understanding of natural selection on age-specific reproductive and survival rates in long-lived species, and its interaction with ecological variation and underlying genetic architecture.
Keywords
Reproduction, senescence, lifespan, women, demographics, HUMAN LIFESPAN