Chapter 8: The Evolution of Social Behavior. What is social behavior? Types of social interactions The Conundrum of Altruism Kin Selection or Inclusive Fitness Reciprocal Altruism. Social Behavior. Group living requires tradeoffs of costs and benefits
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Type Actor Recipient
Gives a warning call (ACTS ALTRUISTICALLY)
Kin Selection is one answer to the puzzle: Hamilton’s (1964) theory of kin selection (inclusive fitness) predicts that altruistic behaviors will be favored by selection if the costs of performing the behavior are less than the benefits to the receiver discounted by the coefficient of relatedness between actor and recipient.
c= the fitness cost to the individual performing the behavior
b = the sum benefits to all individuals affected by the behavior
r = the average coefficient of relatedness between the actor and recipients
Giving the warning call and accounting for kin selection where the cost of giving the call is .3 and the benefit .1 to each of the others and the actor is the sister of the others (r = .5)
c = .3
b = .1 x 8 = .8
r = .5
rb = .5 x .8 = .4
Give the warning call because c<rb (.3 < .4)
Spheres of Interaction and Influence of Kin Selection social interactions.
c < bw
c = cost to the actor
b = benefit to the recipient
w = the likelihood that the actor will receive a benefit in the future as a result of paying the cost now.
Proximity to the Central Hierarchy social interactions.
(After Hall and DeVore, 1965)
Baboons show signs of Reciprocal Altruism
me: R = +3 me: S = -2 C = Cooperate
C D = Defect
you: R = +3 you: T = +5 R = Reward for mutual cooperation
T = Temptation to defect
Me S = Sucker’s payoff
P = Punishment for mutual defection
me: T = +5 me: P = 0
you: S = -2 you: P = 0