Testing the evolutionary theory of senescence in wild vertebrate and historical human populations

Ageing, or senescence, is a central focus of current research across a wide range of biological disciplines, as well as a topic of wider public and governmental concern. Our understanding of the processes responsible for ageing is limited by the paucity of research into the evolution of senescence undertaken in natural settings. Organisms in nature experience an inevitable risk of death from environmental causes, and this leads to a decline in the force of natural selection with age. It is now widely accepted that senescence evolves as a bi-product of this weakening selection. Classical theory predicts that increasing the risk of mortality will result in the evolution of faster senescence rates. However, more recent theory has shown that this prediction is over-simplistic and may not apply outside of the laboratory. Conventional wisdom also states that the weakening force of selection with age allows senescence to evolve via two different genetic mechanisms, known as 'antagonistic pleiotropy' and 'mutation accumulation'. However, the roles that these mechanisms actually play are poorly understood in natural animal populations, including humans. My research will address these two major challenges to our understanding of evolution of senescence. Determining the causes of variation in individual mortality risk and senescence rates in natural populations is required to understand the evolution of senescence. I will use data collected from long-term individual-based studies of four wild vertebrate populations to test the effects of shared genes and environments on variation in adult mortality risk. I will also test for differences in senescence rates associated with sex and environmental quality. In order to test the roles of the two genetic mechanisms thought to be responsible for the evolution of senescence, I will analyse data from wild vertebrate and historical human populations. I will use historical human data sets to provide the first simultaneous tests of both genetic mechanisms of senescence in a natural population. My analyses will produce general, rather than just system-specific, tests of key hypotheses regarding the evolution of senescence in nature. Advancing our understanding of senescence in natural systems will benefit the wide range of biological disciplines involved in research into ageing, including population ecology, evolutionary biology, veterinary and medical sciences, molecular and cell biology and physiology.