PROJECT SUMMARY While one of the most remarkable features of the human species is our capacity for extreme longevity, understanding the marked variation in life spans within and between populations and the capacity for further life span extension are key priorities for aging research. A key insight from research thus far is that early life has an especially important influence on life span differences both within humans and between humans and other species. Given its profound negative impacts on morbidity and mortality risk over the life course, early life adversity is an important source of heterogeneity that also shapes disparities in human health and life span. The widespread nature of these effects in humans and other animals suggests that the mechanisms that underlie them have deep evolutionary roots, making comparative models appropriate and useful for assessing responses to early life adversity across many ecological and social conditions. This study investigates two of humans’ closest living relatives, chimpanzees and gorillas, to determine how variation in the prevalence of and resilience to early life adversity shapes the capacity to achieve long life span in diverse environments. To aid in distinguishing species differences from differences due to local ecologies, we include 2 populations of chimpanzees. The three study systems differ in life span and occupy markedly different ecological and social systems, exposing them to different regimes of adversity. This is a mixed prospective and longitudinal study, leveraging 170 years of detailed demographic and early life adversity data from approximately 400 wild chimpanzees and 485 wild gorillas. Aim 1 will determine the causes, severity, and responses to early life adversity within populations, and between sexes, to quantify its influence on individual risk of mortality and frailty. To accomplish this, we will analyze detailed demographic data and systematic quantitative measures of social and ecological adversities, while generating novel and harmonizable measures of the biological effects of these adversities for both developing and adult individuals. Aim 2 will use these data to determine how different frequency of and sensitivity to adversity shapes heterogeneity in adult cohorts, and in turn influences variation in demographic aging and life span. We will also perform structured comparative models and simulations to evaluate the effects of early life adversity on population and species differences in longevity- influencing life history traits. This project is made possible by three exceptionally rich longitudinal datasets from wild apes, incorporating extensive biological sampling and health monitoring. The project will generate new information that addresses key priorities for research on human life span, including the gender morbidity- mortality paradox, determinants of social gradients in health span and life span, and identifying promising targets for interventions to enhance huma...