EVOLUTIONARY-THEORY PREDICTS LATE-LIFE MORTALITY PLATEAUS

Most demographic data indicate a roughly exponential increase in adult mortality with age, a phenomenon that has been explained in terms of a decline in the force of natural selection acting on age-specific mor tality. Scattered demographic findings suggest the existence of a late -life mortality plateau in both humans and dipteran insects, seemingly at odds with both prior data and evolutionary theory, Extensions to t he evolutionary theory of aging are developed which indicate that such late-life mortality plateaus are to be expected when enough late-life data are collected, This expanded theory predicts late-life mortality plateaus, with both antagonistic pleiotropy and mutation accumulation as driving population genetic mechanisms.