Leonid Gavrilov recently pointed the GRG list to an interesting discussion on the evolutionary theory of aging - complete with thoughtful comments from the likes of Richard Miller, Steven Austad and Andrzej Bartke.
I cannot imagine any theoretical construct more central to biogerontology than the evolutionary biological theory of aging (SN Austad, Why We Age, Wiley, NY, 1997). The theory applies to age-structured populations and to ecologies that dominated the early history of particular animal species. These early nature-nurture interactions shaped the genomes so that their life histories maximized reproductive fitness. In ecologies with high hazard functions, the more optimal life history would be one that involved rapid development, large numbers of progeny beginning shortly after the attainment of sexual maturity, and relatively short life spans. For the case of low hazard environments, a different life history strategy, one involving slower rates of development, longer periods of fecundity and longer life spans, might prove to lead to greater reproductive fitness. Tom Kirkwood's formulation invokes trade offs between the need for energetic resources for reproduction versus the need for energetic resources to maintain the soma (Kirkwood and Holliday, Proc R Soc Lond Biol Sci 205:531, 1979).
It's well worth a read for those of you who are interested in aging research.