Evolution of Aging

1
Evolution of Aging Late Life

• Chapter 18

2
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 Hamiltons Mathematical Forces of
  Natural Selection.

3
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

4
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.

5
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

6
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

7
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