FRAR course on laboratory approaches to aging. The comparative perspective and choice of animal models in aging research.

The comparative perspective may be defined as the assumption that individual species or populations differ from one another in potentially instructive ways, and that an appropriate analysis of the nature and magnitude of these differences will yield insights into fundamental processes of aging. Modern experimental research on aging has largely lost its comparative focus, and virtually all research on mammals utilizes inbred strains of laboratory rats and mice, two closely related species chosen not for their properties vis à vis aging, but for convenience. In fact, from a mammalian life history perspective, humans are at the opposite end of the aging continuum than these animal models and other small species conducive to laboratory research, mimic human life history much better. The comparative perspective may play four roles in aging research: 1) hypothesis formulation and evaluation; 2) assessing the generality of aging mechanisms, typically requiring a choice of several animal models distantly related to one another; 3) isolation of key factors influencing aging rate, requiring model systems as closely-related to one another as possible, but differing with respect to aging rate (intraspecific variation in aging rate is particularly useful here); 4) choosing of animal models with particular properties in mind, such as the spectacularly effective antioxidant systems of bats. Increasing the range of animal models used in aging research will accelerate progress in understanding and perhaps manipulating human aging.