Sex differences in health and survival during aging are major topics of interest in medicine, epidemiology, demography and evolutionary biology. Despite this pervasive interest, and despite a wealth of data on aging in humans and a few well-studied model organisms, patterns of aging in wild animals remain largely undescribed. Studies of aging in wild animal populations, especially in our primate relatives, offer great potential benefits for our understanding of aging in humans. They can provide a comparative perspective on human aging, generate new questions, produce insights into the answers to old ones, and identify opportunities for alleviating the adverse consequences of aging. An overarching goal of this proposal is to fill significant gaps in our knowledge of aging in the wild in order to realize some of these potential benefits. Specifically, we propose to examine age-related changes in health and survival, and sex differences in these age-related changes, in a natural nonhuman primate population. Our motivating question is the health-survival paradox, the phenomenon observed in modern human societies in which women experience greater longevity and yet higher rates of disability than men. It is not known whether the health-survival paradox pertains in wild animal populations. Here we hypothesize that it does pertain, and that many of the same factors that affect survival and health in humans have parallels in wild primates, in spite of important social and physical differences between species. In pursuing the research, we will take advantage of and build upon an existing long-term database of almost unprecedented breadth and depth on the baboon population of the Amboseli basin in Kenya. This population of individually known animals has been under continuous observation for 35 years, and extensive life history and behavioral data have been collected on individually identified animals throughout their natural life spans. By examining individual patterns of survival and health in this population, we propose to provide the first detailed description of sex differences in senescence in a wild primate population. Our analyses will focus not only on the decline in survival with age, but also on changes in health and function with age.
In pursuing our research aims we will identify sex differences in behaviors that create risks, sex differences in the effects of risk factors, and sex differences in the stability and congruence of measures of function. Taken together, our analyses will enable us to identify the nature and causes of the health-survival paradox in wild primates, and by extension in humans.
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