Evolution of Social Behavior Lecture Notes - ANT 201...

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ANT 201: Concepts and Methods in Biological Anthropology Professor: Craig Hadley Department: Anthropology Lecture 12: Evolution of Social Behavior Notes 1. Altruism Behaviors that benefit others at a personal cost. Behaviors such as grooming and alarm calling 1. alliances, cooperative hunting, food sharing, territorial defense, communal care of young 2. alarm calling alerts predator and other animals- risk injury to help others 3. use time grooming instead of looking for food Problem of altruism “selfish” genes passed on Explanation 1: Group selection 1. groups that help one another out-produce selfish groups Explanation 2: By-product mutualism 2. behaviors look like they are altruistic but they aren’t (no cost to actor) Explanation 3: Kin selection 3. related individuals help one another 4. phenotypically altruistic behavior is genetically selfish Explanation 4: Reciprocal altruism 5. “I help you, you help me” – repeat… Fate of an altruistic allele in population callers and noncallers alarm calls are altruistic – increase in fitness of listeners who are more likely to escape predator; decrease in actors fitness non altruist doesn’t give alarm call – relative fitness doesn’t change altruists selected against but benefit more than non-altruists because of nonrandom interactions (alert family members) hearing call increases relative fitness of altruists calling reduces relative fitness of altruists altruists are selected for, if they are common enough 2. Mutualism o Behaviors that benefit both participants.
unrelated individuals may cooperate with one another – can’t explain w/ kin selection o Only beneficial when all parties involved pull their own weight. o lower ranking males may jointly challenge a higher-ranking male to gain control of female he is guarding o coalition among male baboons The Problem with Group-Level Explanations Altruistic behaviors cannot be favored by selection just because they are beneficial to the group as a whole 3.Kin Selection Natural selection can favor altruistic behavior if altruistic individuals are more likely to interact with each other than chance alone would dictate 1. 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 recipient o Hamilton’s theory of kin selection

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