The<unk>  was first proposed by George C. Williams in 1957 as an evolutionary explanation for senescence.<unk>  is the phenomenon where one gene controls for more than one phenotypic trait in an organism.<unk><unk>  is when one gene controls for more than one trait, where at least one of these traits is beneficial to the organism's fitness early on in life and at least one is detrimental to the organism's fitness later on due to a decline in the force of natural selection. The theme of G.C. William's idea about<unk><unk>  was that if a gene caused both increased reproduction in early life and aging in later life, then senescence would be adaptive in evolution. For example, one study suggests that since follicular depletion in human females causes both more regular cycles in early life and loss of fertility later in life through menopause, it can be selected for by having its early benefits outweigh its late costs. Strength of selection plot
Antagonistic pleiotropy hypothesis
Thrifty gene hypothesis
Protein leverage hypothesis
Drifty gene hypothesis
Postzygotic mutation
Lead–crime hypothesis
Functional matrix hypothesis
Weathering hypothesis