ANT 201: Concepts and Methods in Biological AnthropologyProfessor: Craig HadleyDepartment: AnthropologyLecture 12: Evolution of Social Behavior Notes1. AltruismBehaviors that benefit others at a personal cost.Behaviors such as grooming and alarm calling1.alliances, cooperative hunting, food sharing, territorial defense, communal care of young2.alarm calling alerts predator and other animals- risk injury to help others 3.use time grooming instead of looking for foodProblem of altruism –“selfish” genes passed on Explanation 1: Group selection1.groups that help one another out-produce selfish groupsExplanation 2: By-product mutualism2.behaviors look like they are altruistic but they aren’t (no cost to actor)Explanation 3: Kin selection3.related individuals help one another4.phenotypically altruistic behavior is genetically selfishExplanation 4: Reciprocal altruism5.“I help you, you help me” – repeat…Fate of an altruistic allele in populationcallers and noncallersalarm calls are altruistic – increase in fitness of listeners who are more likely to escape predator; decrease in actors fitnessnon altruist doesn’t give alarm call – relative fitness doesn’t changealtruists selected against but benefit more than non-altruists because of nonrandom interactions (alert family members)hearing call increases relative fitness of altruistscalling reduces relative fitness of altruistsaltruists are selected for, if they are common enough2. MutualismoBehaviors that benefit both participants.
unrelated individuals may cooperate with one another – can’t explain w/ kin selectionoOnly beneficial when all parties involved pull their own weight.olower ranking males may jointly challenge a higher-ranking male to gain control of female he is guardingocoalition among male baboonsThe Problem with Group-Level ExplanationsAltruistic behaviors cannot be favored by selection just because they are beneficial to the group as a whole3.Kin SelectionNatural selection can favor altruistic behavior if altruistic individuals are more likely to interact with each other than chance alone would dictate1.Differential interaction (when altruists associate with other altruists) helps facilitate the evolution of altruism. Hamilton’s rule predicts that altruistic behaviors will be factored by selection if the costs of performing the behavior are less than the benefits discounted by the coefficient of relatedness between actor and recipientoHamilton’s theory of kin selection