JAN 27

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6: JAN 27


  • Sapolsky, Chapter 10: The Evolution of Human Behavior 328-387 (59). For this class read only pages 354-374.


  • More rubric training
  • In class discussion of group selection

Some lecture notes on Sapolsky, Chapter 10: The Evolution of Human Behavior 354-374

  • See previous class for reading notes on this chapter
  • How can cooperation get started and become stable? 353-
  • In other words, how does "tit for tat" survive among defectors? Coalitions, green beard effects.
  • Sometimes natural event cut a group off. Inbreeding promotes stronger kin bonds. That group may outperform others once they out migrate. (Give example from Henrich of Inuits with meat sharing behaviors. A better "cooperative package".)
  • Effects of ind. selection, kin selection, and reciprocal altruism:
  • Tournament vs. Pair bonding - lots of traits and behaviors follow from sexual dimorphism. This also happens in degrees.
  • Parent-Offspring competition - in spite of kin selection, there are some "zero sum" situations bt parents and offspring. parent-offspring weaning conflict and mother-fetus conflict. Over insulin. Dad even has a vote through paternal "imprinted genes," which promote fetal growth at expense of mom. (Intersexual Genetic Conflict)
  • Multilevel Selection MLS
  • Remember the "bad" group selection from the beginning of the chapter? Group selection returns in the last few decades. (Tell story of visits with Bio prof friends over the years.)
  • Genotypic and Phenotypic levels of explanation - unibrows.
  • Organism (expressed individual) is a vehicle of the genome, but the genome has alot to say about how the organism turns out. .
  • Big debate in Biology. Three positions: 1. Dawkins took the "selfish gene" view that the best level of explanation is individual genes. 2. Others say the genome - "a chicken is an egg's way of making another egg" (It's the whole genome travelling through evolutionary "space".); finally, 3. Others like Gould take the phenotype. After all, it's visible to the world. Selection could operate on a single phenotypic trait or the whole individual. Dawkins cake metaphor. 362. (So that's really four levels of selection.)
  • Four levels and counting.
  • Fifth level: neo-group selection - the idea that some heritable traits are maladaptive for the individual, but increase the group's fitness (note difference from the bad old group selection).
  • Examples:
  • Encouraging patriotism might lead you to enlist, taking a fitness risk that we benefit from.
  • Jailing someone for their reproductive life is a serious fitness hit, but we're better off with murderers locked up.
  • Neo-group selection happens when groups impose fitness costs or benefits on members or sub-groups.
  • Postive (fitness benefits): zags helping zags, .
  • Negative for some, positive for others(fitness costs): Slavery, racism, class bias, criminal punishment, patriotism, heroism, priests.
  • Some scientists agree that neo-group selection can occur, but think it's rare. Sapolsky points out that it is not rare in humans, due to Green Beard effects.
  • Remember "Green Beard" effects from p. 341 -- a thought experiment in extending/recognizing kin. With neo-group, we go further, and hypothesize that we can form groups around almost anything (sport teams in an imaginary baseball league). Human mind does not limit partiality or commitment to kin or even social group.
  • Where do we fit in? AND US?
  • We're bit of chimp and a bit of bonobo. Men 10% larger, 20% heavier than women. Slight dimorphism. Not quite pair-bonding, not quite tournament
  • US and Individual Selection: Example of divorce: natural experiment when cultural taboos are lifted. Note that increased divorce rates are confined to the same percentage of population. Lift culture and you get to see who the "less pair-bonding" people are! Likewise with historically powerful (and not very romantic) rulers. Point: with absolute power, tyrants often adopt extreme reproductive behaviors with many hundreds of women, if possible.
  • US and Kin selection: Still very powerful, most feuds are clan based, but we can go to war against kin, and we give to strangers. We can be disgusted by people who betray their families: Story of Pavlik Morozov, 368. 368: study about preferring dog to x, y, z. vmPFC involved.
  • Why do humans deviate from kin selection so much. Biologists also want to find mechanisms. Animals recognize kin by MHC or imprinted genes. We do it cognitively. Much more flexibility.