17. Human Mortality from Beginning to End

Evolutionary demographers who study human traits usually focus solely on natural selection as a cause of the trait’s evolution. However, demographic stochasticity, genetic drift, and phylogenetic inertia can also significantly influence trait evolution. We describe why accounting for these influences is necessary in order to correctly test hypotheses about the adaptive nature of human demographic traits. For example, “U”-shaped mortality from the beginning to the end of life is found in many vertebrates, which implies that phylogeny must be considered in understanding its evolution of this trait in humans. Even when these other evolutionary influences have negligible effects on a human demographic trait, it is incorrect to assume that the observed trait must be optimal. Current data and analyses are not sufficient to properly confirm the claim that “U”-shaped mortality rate in humans is the result of natural selection in humans or that it is optimal. We describe the additional data and analyses that are needed in order to properly test these claims.