Cooperation

• Belding's Ground Squirrels


  Alarm-call predators
• Alarm-calls benefit less-vigilant listeners


  Those giving calls more likely to be killed
• The Problem of Altruism
• Altruism


  Benefits another at cost to self (reduces fitness of actor / increases fitness of recipient)
• Three explanations


  • Mutualism
  • Reciprocity
  • Kinship
• Mutualism


  Actor (and recipient) both benefit simultaneously from behavior, not dependent on behavior or identity of others = unconditional
• Mutualism


  • Both work together to get shared food
• Reciprocity


  Actor and recipient trade benefits over time, current behavior of actor depends on past behavior of recipient : scorekeeping, conditional on behavior
• Reciprocity


  • I get food this time, you get it next time
• Kinship


  Actor increases own fitness by helping relatives reproduce = direct + indirect fitness
• Kinship


  Own offspring produced
• Kinship


  Proportion of actor's genes in non-descendant offspring x Non-descendant offspring that survive because of help, Copies of genes identical by descent that are passed on
• Belding's Ground Squirrels: Mutualism?
• Belding's Ground Squirrels: Reciprocity?
• Belding's Ground Squirrels: Kinship?
• Belding's Ground Squirrels: Kinship?


  Alarm-calling could benefit actor by Direct selection for survival of descendant offspring, Indirect selection for survival of non-descendant kin
• Belding's Ground Squirrels: Kinship?


  Direct + Indirect Selection = Kin Selection, Direct + Indirect Fitness = Inclusive Fitness
• Inclusive Fitness


  Direct Fitness + Indirect Fitness, Descendant offspring (x relatedness), Offspring of relatives (due to help) (x relatedness), Copies of genes identical by descent that are passed on
• Coefficient of Relatedness (r)


  Average proportion of genes that will be identical by common descent in two individuals
• Coefficient of Relatedness (r)


  • Example: Mother - Daughter
• Coefficient of Relatedness (r)


  Full Siblings: Genes in common from mother, Genes in common from father, Total average proportion identical by descent
• Hamilton's Rule


  Help when: C * r_c < B * r_b, Reproductive Cost (# offspring) to actor, Relatedness to actor of offspring (C) given up by actor, Repro. Benefit (# offspring) to recipient, Relatedness of offspring (B) to actor
• Simple Case

  • When should a parent give its life for its offspring? C*1 < B*1/2, or B/C > 2; i.e. for more than 2 offspring. Assumes: parent can replace offspring. If no further RS possible, pays parent to sacrifice self for any number of offspring!
• Wild Turkey Coalition
• Three explanations for apparent altruism


  • Kinship (e.g. alarm-calling ground squirrels)
  • Reciprocity (e.g. vampire bat blood-sharing)
  • Mutualism
• Kinship


  • Alarm calling rodents, Helpers at the nest birds, canids, Insect eusociality bees, ants, termites, Cooperative territory defense birds, canids, lions, Communal nursing lions
• Reciprocity


  Costs & benefits to actor separated in time, Scorekeeping requires cognitive abilities
• Game Theory Approach


  Origin: analysis of human conflict, John Maynard Smith: adapted to analyze evolution & behavior, Players adopt a strategy (could be genetically determined), Payoff to strategy depends on other strategies in game, Analysis of decisions when payoffs are frequency dependent, A strategy that does best against itself and all other strategies in the game is an ESS (Evolutionarily Stable Strategy)
• Prisoner's Dilemma


  T > R > P > S, reward, temptation, sucker's, punishment
• Lessons: Reciprocity requires
• Examples of Reciprocity


  • Vampire bats (blood meals), Apes (social favors), Fish (egg-trading in hermaphrodites)
• Mutualism


  Each participant benefits immediately, Benefits > Costs
• Examples of Mutualism


  • Cooperative foraging, Meerkat sentinels, Coalitions in lions, primates