Evolution of Aging and Late LifeChapter 18Experimental Evolution

Does aging have a purpose?Is it adaptive?

What is aging?Think-Pair-Share

Does natural selection act on aging?

Does aging evolve?

What is aging to an evolutionary biologist?Think-Pair-Share

We used to think…

…aging evolved to eliminate older individuals to make way for the young.

Why is this false? Think-Pair-Share

EVOLUTIONARY THEORIES OF AGING?

What are the

Hamilton’s Forces of Natural Selection

The force of natural selection acting on survival falls with adult age.

If natural selection isn’t acting on aging, does aging evolve?

How can we test theories of aging?

1.) Early reproduction will accelerate aging in population.

2.) Late reproduction will slow aging in population.

If Aging has evolutionary basis

Model OrganismDrosophila melanogaster

• Well established laboratory organism

• Used in experimental evolution studies

• Short life-span• Easy to manipulate

Results show aging is evolutionaryDrosophila melanogaster

LATE LIFE

How many life stages do you see represented in this graph?

Think-Pair-Share

What explains extreme old age?

Discovery of Late Life

• An evolutionarily distinct phase of life • Evolves with different rules than those of

early life and aging.