Arguing for More and Better Studies of the Comparative Biology of Aging

In this open access paper, the author argues for greater investigation of the fundamentals of aging in various species, for more comparisons of the biochemistry of aging between wild and laboratory populations, and for greater collaboration between some of the distinct communities within the aging research community:

Aging (senescence) is an increase in mortality risk with age due to deterioration of vital functions. Understanding the mechanisms and consequences of aging is not only an intriguing evolutionary question but also a matter of practical concern with pressing demographic and societal implications. The two aspects of aging research - fundamental understanding of why organisms age and how aging patterns in nature vary on the one hand, and an applied perspective dealing with biomedical treatments of aging on the other - have entered an exciting phase. I argue that the next steps to understand the biology of aging should combine approaches and concepts used by the two research communities.

Biogerontologists are interested in proximate mechanisms of aging, use laboratory models and focus on means of mitigating specific functional declines associated with aging. Advances in biogerontology have demonstrated that these proximate mechanisms of aging and interventions to modify lifespan are shared among species. Evolutionary biologists seek to understand why aging has evolved and how and why it varies among populations and species. Long-standing theories to explain the evolution of aging have recently been found unsatisfactory in their ability to explain many observed patterns of aging, revealing how incomplete our understanding of the evolutionary aspects of aging (and variation in aging rates within and among species) currently is. A systematic feedback between functional and evolutionary research on aging is needed to provide mutually beneficial critical insights into the biological basis of aging.

In nature, aging patterns have proven more diverse than previously assumed. The paradigm that extrinsic mortality ultimately determines evolution of aging rates has been questioned and there appears to be a mismatch between intra- and inter-specific patterns. The major challenges emerging in evolutionary ecology of aging are a lack of understanding of the complexity in functional senescence under natural conditions and unavailability of estimates of aging rates for matched populations exposed to natural and laboratory conditions. I argue that we need to reconcile laboratory and field-based approaches to better understand (1) how aging rates (baseline mortality and the rate of increase in mortality with age) vary across populations within a species, (2) how genetic and environmental variation interact to modulate individual expression of aging rates, and (3) how much intraspecific variation in lifespan is attributable to an intrinsic (i.e., nonenvironmental) component. I suggest integration of laboratory and field assays using multiple matched populations of the same species, along with measures of functional declines.


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