Evolutionary Adaptation

"Survival of the fittest"

Artificial Selection

• Heike crabs

Natural Selection

• Ants

Survive to Reproduce

• Not all animals survive long enough to have offspring
  • Their genes are "lost"
• Select for characteristics that improve chance of survival and reproduction
  • These genes will be passed on (inherited)

Mechanisms of Evolution

Genes

• The units of evolution
• Genes and proteins
• Proteins influence behaviour
• Behaviour effects chance of survival

Mutations

• Ultimate source of genetic variation
• Lethal, neutral, or beneficial

Environmental Change

• Alters advantages/disadvantages of:
  • Specific genes
  • Gene/gene interactions
  • Polygenetic effects
• Environmental change does not cause mutations
  • Allows natural selection to work

Behaviour

• Behaviours that let an organism fill a niche more successfully evolve
• e.g., human brain
  • What was lost? What was gained?

Levels

Levels of Adaptation

• To adapt is to change to suit new conditions
• Three levels:
  • Evolutionary
  • Individual
  • Cultural
• Are the three levels really distinct?

Ultimate and Proximate Causes of Behaviour

• Ultimate
  • Functional explanation at evolutionary level
• Proximate
  • Mechanistic explanation about immediate conditions leading to the behaviour
• Not all behaviours are adaptive! 

Additional Considerations

Genetic Drift

• Any change in the gene pool due to chance alone
• Natural selection is not involved
• Founder effect
  • Genetic difference between populations
  • Due to small number of individuals who started the population
• e.g., Pitcairn Island and blue eyes

Correlates of Structure

• Non-adaptive trait develops along with an adaptive trait
• Organs, and behaviours, do not have to serve just the function they evolved for
  • e.g., Brains and VCRs

The Whys (Wise?) of Evolution

Evolution Is Blind

• No foresight in evolution
• Organisms go through a "filter" that determines if their genes are passed on
• No ultimate goal or purpose of evolution

Dawkins

• The "selfish gene"
• Suggests life only exists to pass on genes
  • Organisms are "carriers" for genes

Thoughts to Think...

Does natural selection still operate on humans? Consider all the people that wear glasses.

What will happen to the prevalence of a recessive gene in a population started by the founder effect?

If not all animals survive to reproduce, is there not the risk that beneficial genes could be lost from the population?