1. Food and Moving onto the Savannah What is social behavior?
Chapter 14: The Evolution of Social Behavior – Behavioral Ecology and Sociobiology/Evolutionary Psychology
Food and Moving onto the Savannah
What is social behavior?
Types of social interactions
The Conundrum of Altruism
Kin Selection or Inclusive Fitness
Reciprocal Altruism

2. Food and Moving onto the Savannah
Tastes
Meat:
Rich source of nutrition by weight
Few or little poisons
“Man the Hunter” (Lee and DeVore).
Geographic spread
Meat for sex: marriage
Reciprocity: “The Sex Contract” (Helen Fisher)
Meat for kids: family
Kin-Selection

3. Meat for friends: coalitions/politics
Hunting Return Variance problem
Risk sharing and Reciprocal Altruism
Meat for status
Trophies and Showing off
Other hunting adaptations
Optimal foraging strategies
More in Chapter 15
Vegetables don’t have minds
Cost and benefits
Weapon use
Perhaps music?

4. Plants Largest contribution to diet Other primates
“Women the Gatherer”
Less risky than hunting
Less travel distances
Roots (Wrangham)
Baboons
Sex differences in spatial abilities

5. Sexual division of labor is a human parenting strategy based on reciprocity
Implies a contract between men and women
Monogamy and Fatherhood (Human Universals)
Apes to Hunters and Gatherers
Savannah are dispersed and low density
High childhood mortality
Need Father to provision and protect
Household based economies
Central Place Foraging pattern
Sharing between households
Networks of households
Lineage based social groups (patrilocality)
Which came first?

6. Social Behavior Group living requires tradeoffs of costs and benefits
Social interactions are behaviors that has a fitness consequences for two or more individuals (of the same species).
Excludes:
Parenting
Mating
In a social interaction there is an ACTOR and a RECIPIENT(S) of the action.
An action can be said to be beneficial (+) if it increases fitness, and costly or detrimental (-) if it decreases fitness.

7. Types of Social Interactions
A taxonomy of pair wise, or dyadic, social interactions based on fitness outcomes:
Type Actor Recipient
Selfish
Mutualistic
Altruistic
Spiteful

8. The Conundrum of Altruism
Selfish and mutualistic acts increase the fitness of the actor. It is clear that these behaviors will be selected for by natural selection, because those who act selfishly or mutualisticly derive a direct/immediate benefit from their action.
Altruism is a problem to explain because by definition it decreases the fitness of the individual performing the behavior while increasing the fitness of a competitor (the recipient) and therefore reduces the contribution of the genes that underpin that behavior to the next generation.
Even spiteful interactions can be explained by natural selection as long at the recipient pays a greater fitness cost than the actor.

9. Altruism and Warning Calls
Gives a warning call (ACTS ALTRUISTICALLY)
                                                  

10. Doesn’t give a call (ACT SELFISHLY)

11. c<br c = the fitness cost to the individual performing the behavior
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<br
where
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

12. Give the warning call because c<rb (.3 < .4)
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)

13. Kin selection is a powerful motivation for cooperation in social interactions.
Kinship is an important principle for the organization social structures
In tribal and band societies kinship is the primary principle around which groups form and is primary in defining the relationships between groups

15. Spheres of Interaction and Influence of Kin Selection
Intertribal 

16. Among the Yanomamö the value r in Hamilton’s Rule:
Is related to how large a village gets before fissioning
Predicts who will side with whom during conflicts
Predicts who will go with whom when a village fissions
Kinship is likely the most important principle underlying group structures in the EEA
What about chimp social structures?
Kinship is also used as a principal for organizing non-kinship based organizations like religion

17. Reciprocal Altruism (Trivers 1971)
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.

18. Baboons show signs of Reciprocal Altruism
Dano
(18)
Pua
(8)
Kovu
(11)
Dominance
Rank
Modomo
Kula
Mark
(0)
(After Hall and DeVore, 1965)
Proximity to the Central Hierarchy

19. Game Theory: Tit for tat and the Prisoner’s Dilemma
YOU
C D
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 D
you: S = -2 you: P = 0

20. In a one-time game, you should defect because the average payoff is greater.
If the game is to be repeated many times (as is the game of life), it is in both player’s long-term interest to cooperate.
In game theory the value w is defined as the number of times the game will be played
Tit-for-tat is an evolutionarily stable strategy, or solution, to a repeated Prisoner’s Dilemma game. The rule is: cooperate on the first play and then do what your opponent did in the last play.
Also known as the Golden Rule
All social interactions, like games, are competitive (winners and losers)
Assignment: go to and do the tutorial on the Evolution of Cooperation.

21. Evolutionary Psychology is the study of Human Nature
Species Typical Behaviors
Innate cognitive mechanisms for making decisions concerning specific evolutionarily stable (ES) problems and motivate actions based on these decisions.  This involves: 
Adaptations for perceiving, recognizing, and making salient appropriate inputs to determine if a ES problem exists, and assessing the costs and benifits. 
Choosing between possible solutions (STRATEGIES) to problems using the gathered inputs and filling in the blanks when information is incomplete.
Attaching appropriate emotional states that motivate actions that lead to probable solutions to ES problems.

22. Deep-Blue and Casperoff
The goal of this new science of the mind is to map out all of the decision-making rules that make up human nature.
Deep-Blue and Casperoff
Human Nature must be universal with low tolerance for variability
Shirley McLain and Sybil Theories of Evolutionary Psychology
Focus is on the design features of adaptations rather then on RS
Adaptive mismatch problem

23. Social contracts and the logic of detecting cheaters:
The Wason Selection Task (Leda Cosmides)
Clerical Problem
Rule: If a person has a ‘D’ rating, then his/her documents must be marked with a ‘3’ D F 3 5

24. Bartender’s Problem
Rule: If a person is drinking a beer, then he/she must be over 21 years old’
25 years old
17 years old
Drinking a beer
Drinking a coke

25. Both the Abstract and Social Contract problems are logically identical (P, not Q)
Significance :
We have specialized cognitive mechanisms (adaptations for making decisions) for policing social contracts: CHEATER DETECTION
If you don’t pay the cost you are not entitled to the benefit (Reciprocal Altruism and Tit-for-Tat)
The mind is modular:
Functionally specific not just capacity for reasoning
Abstract (clerical) problem not in the form of a social contract and we don’t turn on the cheater detection module to solve it.

26. Human Universals Color Terms Hopi time and 7 Words for Snow
Incest Avoidance
Kabbutz
Chinese Child Brides
Expressions of Emotions
Social Structures
Near Universals
Universals: Innate Human Nature or Universal Experience

27. Human Behavioral Ecology
Humans are rational actors who act in ways to maximize their reproductive fitness
Adaptations lead to RS
Phenotypic Gambit (Black Box)
Optimization vs. Maximization
Long term cost and benefits
Lack: clutch size in birds
Optimal family size (child spacing) in Chapter 19
Optimal foraging strategies
Game choice
Size of hunting parties