Why Do We Die? Lifespans as an Evolutionary Optimum

Abstract:     
Animals display wide diversity in lifespans. Some tantalizing empirical relations relationships have been observed about lifespans. One is that for mammals lifespan increases with brain size, and decreases with size and metabolic rate. The challenge for any theory is to explain these observations. A "wear and tear" theory of lifespan postulates that the metabolic rate determines the rate of "wear and tear" of tissues and hence lifespans. However this leaves unanswered the question why organisms with high metabolic rates possess this seemingly undesirable characteristic which reduces their lifespans. This paper proposes a theory in which lifespan and metabolic rates are the optimal response to natural constraints. Evolution chooses for an animal the optimum mix of lifespan and metabolic rate.

Number of Pages in PDF File: 8

Keywords: lifespan, evolution, hormones, cobb-douglas

JEL Classification: A12, D6, Z00, Q2, Q3

working papers series