Introduction

Abstract

Death is part of life, and it can strike any time. The question is whether death necessarily becomes more likely as life proceeds. William D. Hamilton (1966), one of the leading biologists of the last century claimed that senescence is inevitable¹ because the force of selection declines with age, making later ages unimportant to evolution. Survival and reproduction are the key players in this game and they are the traits negatively affected when selection loosens its grip.

The word “aging” is often used instead of the narrower, more precise but less common word “senescence” to describe a decline in physiological functioning with age. Hence I chose to entitle this monograph “Inevitable aging?” instead of “Inevitable senescence?”. Throughout the monograph, however, I make a clear distinction between aging and senescence: I use the term aging to refer to any kind of variation in functioning with age, for the better or worse, and reserve the term senescence for a deterioration in functioning.