Cooperation

Cooperation

1. 3 theories

   • Kin Selection
     • INCLUSIVE FITNESS
       • Direct fitness = via reproduction
       • Indirect fitness = increasing the fitness of individuals likely to share your genes
       • HAMILTON'S RULE 1964
         • describes mathematically whether a gene for altruism will spread in a population
         • r B > C
           • r = coefficient of relatedness (probability of shared alleles due to recent common ancestry
             • Half sib: 0.25 Full sib: 0.5 Cousins: 0.125
           • B = benefit to recipient (no. extra offspring gained)
           • C = cost to actor (no. of extra offspring lost)
         • Greater relatedness within than between groups
           • e.g. Yanomami ax fight: choosing sides in a dispute on the basis of kinship obligation and shared histories
         • "Cinderella effect" : increased risk of infanticide if the child lives with non-related step-parent.
           • Daly and Wilson 1996: instances of child abuse towards non-biological offspring should be more frequent than towards biological offspring
             • Daly & Wilson 1999 : "a child under three years of age who lived with one genetic parent and one stepparent in the United States in 1976 was about seven times more likely to become a validated child-abuse case in the records than one who dwelt with two genetic parents"
               • based on data from child abuse report archive
             • Daly and WIlson 1985: victims per 1000 children in population highest in one natural + one step-parent households.
               • 0-4 : 40% 5-10 : 19% 11-16 : 10%
               • household circumtances survey + information on child abuse victims, runaways, and juvenile offenders
   • Reciprocal Altruism
     • Trivers 1971: behaviour that temporarily reduces the actor's fitness and increases the recipients' fitness, with the expectation that the recipient will return the favour at a later time
     • GAME THEORY: 'Prisoners' Dilemma'
       • Safer option is to defect, best option is to both cooperate
         • Problem of free-riders, but is still ESS
           • Axelrod & Hamilton 1981: insuring ESS
             • -frequent interaction -tracking of give and take -non-random interactions
               • Humans: punishment (even if costly)
             • Direct reciprocity: returning favours in repeated cooperative interactions. Indirect reciprocity: cooperating with another on the basis of a known probability that they will return the favour or in hope of building own reputation
   • Costly Signalling
     • Zahavi 1975: HANDICAP PRINCIPLE
       • Show quality through honest, costly behaviours
     • RELIGION
       • rituals and taboos hard to fake signals of commitment to group
         • increases intragroup cooperation
       • Sosis & Bressler 2003: costlier the signals, the greater the longevity of the group
         • Proximate: signal commitment promotes intragroup cooperation. Ultimate: this increases individual fitness

2. Food sharing: TOLERATED THEFT

   • Unique to hunter-gatherers
   • 1. Curve of diminishing reurns
     • 1st portions valuable to hungry forager. Once full, subsequent portions worth less
       • Worth a lot to more successful hunter
         • benefit of retaining food outweighed by cost of defending it
         • increase total value of resource packet over its nutritional value
   • 2. 'Show-off' Hypothesis
     • target risky resources with high rate of return -> share catch -> increased matings, offspring survivorship, status
   • 3. Group Membership
     • Western cultures: cooperation even when kin or reciprical alturism acts lack
   • Dilemma: food sharing reduces fluctuations in daily resource consumption of group. But often c/b ratio differ between individuals and to whole group

3. HUMANS UNIQUE

   • 1. Cooperation with strangers
     • 'big mistake hypothesis': imperfect kin-detection systems. Evolved with surrounding kin in human history -> no need to improve. Use physical, behavioural + cultural cues
     • Direct reciprocity: artefact from small to large scale cooperation. Easy trackage in tit-for-tat. Free-riding has emerged from growing population.
   • 2. Altruistic punishment
     • = perform costly punishment even in knowledge it will not benefit them
       • 'Second-order social dilemma': not punishing to max own short-term fitness instead of group long-term fitness
         • SOLUTION: instalment of institutions. Costs shared by all members. Socially imposed norms and rules further reduce risk of non-cooperators
       • e.g. partner switching?
   • 3. Indirect Reciprocity
     • Other animals show simple form but humans show it to greatest extent
       • cognitive capacities enabling memory for long-term tracking of give and take, communication enabling knowledge of others' reputation, assessing reputation by 'image scoring' + 'standing'
   • 4. Shared Goals
     • LANGUAGE
       • communicate own goal and influence others'
         • create FALSE MENTAL REPRESENTATION -> facilitating free-riders?
           • SOLUTION: costly signalling
           • Henrich: 'Credibility Enhancing Displays' (CREDs)
             • = acts providing reliable measure of commitment
             • Martyrs and paragons of virtue: prestige directs who to imitate - CREDs confirm commitment to beliefs
               • Indirect inheritance - memes contributing to cultural pool.
       • Empathy: felt when one adopts perspective of others in need
     • = genuine desire for others with shared goals to succeed - coop not just selfish tool
   • 5. Group Selection
     • 'MULTI-LEVEL SELECTION'
       • higher level: selection between groups -> favours cooperators
         • groups grow faster
       • lower level: selection within groups -> favours defectors
   • 6. Tolerated Theft