Evolution of Aging & Late Life Chapter 18

Evolutionary Definition of Aging Sustained age-specific decline of fitness related characteristics not due to external environmental factors Not possible to study in vast majority of species in wild Based on Hamilton’s Mathematical Forces of Natural Selection.

Population Genetic Hypothesis for Aging Antagonistic Pleiotropy Evolutionary Trade-off, alleles with early benefit produce bad side effects later Mutation Accumulation Decline of force of natural selection fails to remove deleterious mutations

Role of Experimental Evolution in Aging If Aging has evolutionary basis- 1.) Early reproduction will accelerate aging in population. 2.) Late reproduction will slow aging in population.

Results Some experimental results consistent with Antagonistic Pleiotropy mechanism for evolution of aging Other experiments support conclusion that Mutation Accumulation contributes to aging in Drosophila Aging easily identifiable product of evolution involving many genes

Discovery of Late Life Studies of populations revealed that mortality rates increased exponentially during mid-life, plateau later. Two theories- 1) Natural selection drops to zero after reproduction has ended 2) “Lifelong heterogeneity” differences in robustness of individuals

Results Late-life plateaus change with changes in end of reproductive age. 1) Antagonistic Pleiotropy possible genetic mechanism No indication lifelong heterogeneity factor in Late-life plateaus