Understanding the evolution of long lifespan and senescence in humans benefits from a better understanding of these phenomena in the most primitive of our primate relatives. At a recent workshop sponsored by the National Institute on Aging, leaders in the field of human aging called for more research on aging in nonhuman primates. How and when do primates become old? Increasingly it is known that long lifespans are not unique to humans, apes, or even monkeys. The smallest-bodied primates are cheirogaleids (mouse lemurs and their relatives) and studies in captivity show that mouse lemurs can live almost ten times longer than like-sized nonprimates such as mice or shrews. Therefore, because even the most primitive of extant primates are long-lived when compared to like-sized mammals in other orders, it is essential that such an analysis begin with our most distant cousins, lemurs. This is particularly important because in captivity, certain lemurs are known to develop Alzheimer's-like plaques and tangles in aged individuals. This project seeks answers to these questions through research focusing on two lemur species Microcebus rufus, the brown mouse lemur, and Propithecus edwardsi, Milne Edwards' sifaka, in their natural habitat in a single rain forest, Ranomafana National Park, eastern Madagascar. These are the smallest- and largest-bodied primates at this location. The project uses dental, hormonal, behavioral and experimental data to test a variety of hypotheses regarding the evolution of senescence. A new method of dental senescence analysis will be used to measure age in wild sifakas and mouse lemurs. Correlates of aging will be tested in both species by examining three somatic landmarks: muscle function, brain function, and dental function. Finally, reproductive landmarks and reproductive success will be examined in both young and old female lemurs. Taken together, these data will provide insights into the timing of reproductive and somatic senescence in distant relatives of humans, thereby indicating aspects of human aging that may have deep evolutionary roots. This project will engage people of a variety of backgrounds and experience, including undergraduates and graduate students from several countries (including the USA, Finland, Germany, Argentina, and Madagascar). The research team will work closely with Madagascar's National Park Service staff. The Centre ValBio at which this study will be based employs 65 local Malagasy people as biodiversity field technicians. In addition to contributing to aging research, this work will have conservation implications that can be used to inform management plans.
