The Reproductive-Cell Cycle Theory of Aging
There is no shortage of theories of aging: "The Reproductive-Cell Cycle Theory posits that the hormones that regulate reproduction act in an antagonistic pleiotrophic manner to control aging via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence. ... The theory is able to explain: 1) the simultaneous regulation of the rate of aging and reproduction as evidenced by the fact that environmental conditions and experimental interventions known to extend longevity are associated with decreased reproductive-cell cycle signaling factors, thereby slowing aging and preserving fertility in a hostile reproductive environment; 2) two phenomena that are closely related to species lifespan - the rate of growth and development and the ultimate size of the animal; 3) the apparent paradox that size is directly proportional to lifespan and inversely proportional to fertility between species but vice versa within a species; 4) how differing rates of reproduction between species is associated with differences in their lifespan; 5) why we develop age-related diseases; and 6) an evolutionarily credible reason for why and how aging occurs - these hormones act in an antagonistic pleiotrophic manner via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence."