I propose a novel evolutionary approach for studying ecological and demographic factors that affect senescence and lifespan in humans. Women are unique among animals due to menopause and a prolonged lifespan after last birth. Evolutionarily, the quest of everyone is to maximise grandchildren numbers. Hence, human women life-history is enigmatic. One possibility is that older women increase their fitness by directing resources to already produced offspring rather than having more. Thus, although women gain most grandchildren from own reproduction, they also gain more by helping offspring. This has fascinating implications. All animals must split their energy between reproduction vs. self-maintenance. Most continue to reproduce until death and produce maximum grandchildren by optimising investment between current vs. future reproduction. Human women must also optimise investment between mothering and grandmothering. How this is done and affected by ecological, social and demographic factors is unknown, but is essential to understanding the ecological and genetic basis of reproduction, senescence and lifespan. My project has 5 aims: 1. How does reproductive effort affect reproductive and post-reproductive senescence? 2. What proportion of grandchildren is gained post-menopause and how is this modified? 3. Is there heritable variation in life-history traits and their senescence, and how do genetic correlations affect evolution? 4. How do patterns of fitness acquisition account for menopause, prolonged post-reproductive lifespan and age of death in humans? 5. How does fitness maximization differ between men and women and affect their lifespans? The questions will be answered using unique data on three generations of individuals that lived before healthcare and modern contraceptives in Finland. The results will have important implications for predicting demographic structure and will appeal to a wide range of people within and outwith the scientific community.
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