ABSTRACT
With respect to the first question, we can easily respond with ‘‘no’’: The reproductive period of a Homo erectus, who lived 1 million years ago, normally lasted from 12 to 25 years of age. Fossil remains suggest a human life expectancy of approximately 25 years for humans in this period [1]. Thus, natural selection has limited opportunity to exert a direct influence over the process of aging because the advantageous or disadvantageous genes are not conserved after the reproductive period. As recently pointed out [2], this situation allows a wide range of alleles with late deleterious effects to accumulate over generations with little or no check. Under these conditions we might expect considerable heterogeneity in the distribution of such alleles among individuals within the population. Another theory suggested that pleiotropic genes with good effects early in life-e.g., fertility with elevated levels of estrogens in females-would be favored by selection even if these genes had bad effects at later ages [2]. In conclusion, no advantageous or disadvantageous genes are specifically conserved for successful aging.
