Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

Variability (mutation)

Differential fitness (success in leaving progeny) Then what happens?

1. Versions that confer more fitness will become more prevalent over time

Sociobiology is the study of the evolution of behavior. What are the three core explanatory pieces you should be able to apply to a wide range of behavior?

1. 
   Individual selection. "A chicken is an egg's way of making another egg." -Samuel Butler
   
2. 
   Kin selection/inclusive fitness. "I will lay down my life for 2 brothers or 8 cousins" -JBS Haldane
   
3. 
   Reciprocal altruism.
   

Five pieces of evidence for evolution?

1. 
   Observable over past 100 years in short-lived species like staph bacteria & penicillin resistance
   
2. 
   Fossil record shows tons of intermediate forms
   
3. 
   Genetic evidence: we share huge percentages of our genomes with our closest evolutionary ancestors, and less the further you go back in time to most recent common ancestor
   
4. 
   Geographic distribution of species: relatives are bunched together in space
   
5. 
   Unintelligent design: vestigal structures like leg bones in dolphins, pyramidal system for finger movement
   

In our class: natural selection and sexual selection are different (sometimes opposing) forces.

How do they apply to individual selection?

1. 
   Natural: adaptedness to surviving in the environment
   
2. 
   Sexual: adaptedness at attracting a mate
   

How do they apply to kin selection (inclusive fitness)?

1. 
   Natural: Engage in behaviors that allow related individuals to survive and reproduce
   
2. 
   Sexual: Work to make related individuals seem attractive to potential mates How do they apply to cooperation/altruism?
   

1. 
   Natural: non-related hunters cooperating to get game they couldn't get alone.
   
2. 
   Sexual: cooperatively making a non-relative more attractive to mates
   

How do you calculate degrees of relatedness?

1. 
   50% gene-variant similarity with parent or full sibling. 25% with grandparent. 25% with (biological) aunt/uncle. 12.5% with great grandparent, etc.
   
2. 
   Each "line" in the family tree that you traverse typically halves the number of genes you share with the next individual.
   

Cooperation

1.