ABSTRACT
We now turn to the final stages of the life span, a period that is often defined by a gradual decrease in body function eventually ending with death. Why do we age? It is an ancient lament; the question of aging has no easy answer, and in fact it may mark our ignorance of the process. Does aging differ in our later years from in our youth? That is, is aging a cumulative, gradual process, or is it, like growth, marked by varying rates or critical periods of special import? Can the aging process be stopped, or at least slowed? Is aging a natural characteristic that accompanies life, or is it a process that has undergone natural selection, evolving in some (most? all?) populations?
