Ovarian aging in developmental and evolutionary contexts.

Evolutionary theory predicts that aging-related fertility declines result from tradeoffs between reproduction and somatic maintenance. Developmental programs for oogenesis also contribute to variation in aging-related reproductive declines among female vertebrates. Documented reproductive aging patterns in female vertebrates, including humans, are consistent with canonical aging patterns determined developmentally and require no special adaptive explanation. Here we discuss patterns of aging-related ovarian decline in diverse female vertebrates, and place human ovarian aging in comparative context. Depletion of finite oocyte stores accompanied by fertility loss occurs in a variety of nonhuman mammals and vertebrates, including short-lived rodents, birds, and some fishes; moreover, postreproductive lifespans of considerable length clearly are not limited to long-lived, social species with well-developed kin networks. We argue for a more rigorous comparative approach for understanding the evolutionary and developmental bases of ovarian aging in vertebrates with a wider range of aging patterns and social structures.