Evolutionary theories of aging can explain why we age.

Evolutionary theories of aging explain why we age. These theories take into account the fact that, in the wild, mean lifespan of many species is usually shorter than it could be in protected environments. In such conditions, because most of animals die before reaching old age, there is no selection in favor or against alleles with effects at old age. Alleles with negative effects at this age can thus accumulate in successive generations, particularly if they also have positive effects at young age and are thus retained by selection. This chapter describes the evolutionary theories of aging and their consequences for the understanding of the biology of aging as well as the challenges to these theories. It is argued that these theories offer a reasonable explanation to the existence of the aging process even if they can surely be refined.