THE EVOLUTION OF AVIAN SENESCENCE PATTERNS - IMPLICATIONS FOR UNDERSTANDING PRIMARY AGING PROCESSES

The long life spans of birds relative to those of mammals are intrigui ng to biogerontologists, particularly in light of birds' high body tem peratures, high blood glucose levels, and high metabolic rates-all of which should theoretically increase their biochemical liability for ra pid aging. The comparative longevity of birds and other flying homeoth erms is consistent with evolutionary senescence theory, which posits t hat species with low mortality rates from predation or accident will. be released from selection for rapid maturity and early reproduction, and will exhibit retarded aging. Comparative analyses of avian life hi story parameters to date, although not as extensive as those for mamma ls, broadly support an association between low mortality rates, slow r eproduction, and long lifespan. The diversity of bird life histories s uggests the importance of developing a diversity of avian models for s tudies of aging mechanisms, both proximate and ultimate, and for using wild as well as domestic representatives. Birds studied in the labora tory thus far show many of the same manifestations of aging as mammals , including humans, and many ornithologists are beginning to document actuarial evidence consistent with aging in their study populations. W e encourage greater communication and collaboration among comparative gerontologists and ornithologists, in the hope that the study of aging in birds will lead to an integrated understanding of physiological ag ing processes well grounded in an evolutionary paradigm.