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