MUTATION AND SENESCENCE - WHERE GENETICS AND DEMOGRAPHY MEET

Two evolutionary genetic models-mutation accumulation and antagonistic pleiotropy-have been proposed to explain the origin and maintenance o f senescence. In this paper, we focus our attention on the mutation ac cumulation model. We re-examine previous evidence for mutation accumul ation in light of new information from large-scale demographic experim ents. After discussing evidence for the predictions that have been put forth from models of mutation accumulation, we discuss two critical i ssues at length. First, we discuss the possibility that classical frui t fly stock maintenance regimes may give rise to spurious results in s election studies of aging. Second, we consider evidence for the assump tions underlying evolutionary models of aging. These models assume tha t mutations act additively on age-specific survival rate, that there e xist mutations whose effects are confined to late age-classes, and tha t all mutations have equal effects. Recent empirical evidence suggests that each of these three assumptions is unlikely to be true. On the b asis of these results, we do not conclude that mutation accumulation i s no longer a valid explanation for the evolution of aging. Rather, we suggest that we now need to begin developing more biologically realis tic genetic models for the evolution of aging.