Volunteer chooses to help rebuild power plant despite health consequences. Only certain people can do these type of jobs: he’s young and single
Risk reducing own reproductive success for the better of someone else
Charles Darwin called it struggle for life most severe (p. 2) in relation to survival of the fittest
Became interested in cooperation as a grad student studying mathematics and bio at University of Vienna
Learned about game theory paradox (Prisoner’s Dilemma) while in the Alps
All individuals were defecting, then cooperate, mirror opponents move  change led to communities being dominated by cooperation
Direct reciprocity: individuals cooperating with one another when see each other repeatedly
Ex. vampire bats: if misses to feed on prey, ask from peers. Peers will regurgitate meal into bat’s mouth
Bats remember which bats helped them
Different kinds of direct reciprocity
Player s cooperated even if rival defected  forgives Spatial selection: cooperators and defectors not equally distributed ex. in yeast cells to digest sugar at cost to themselves defector yeast mooch off copper. Enzyme instead of making own in well-mixed pops, defectors prevailed; pops with clumps of coop., coop prevailed
Kin selection: make sacrifices for relatives b/c share same gene; still spreading genes even though lowering own direct reproductive success
Indirect reciprocity: help someone due to the needy one’s reputation
I help you and someone will help me, doesn’t have to necessarily