Social Groups -species range from solitary to complex social groups -costs and benefits to group living?
-mating pairs -vary in stability and duration -aggregates due to environmental conditions -social group osocial relationships, dominance hierarchies -eusocial colonies, societiesotruly social odifferent labor for different individualoex. Work bee, honey bee…Group Living -factors influencing costs and benefits opredation risks odistribution of resources -predation risk influences costs and benefits of group defence -clumped versus dispersed food (or other resources influences cost:benefit of finding and defending themHuman Group Living -evolutionary factors? osavannah habitat in the EEA? oincreased predation risk all modern terrestrial primates are social oclumped food resources large grazing animals-species comparisonsochimps and gorillas are social group-livers obut! low predation risk, and distributed food resources (despite some cooperative hunting)-Why are large apes social?odefense against conspecifics risk of infanticide lead to female groups female groupleads to benefit in female, male is just a by-productFemale-defense polygynyOne male keep other out from his group-Human Group Living opotential combination of increased predation risk cooperative group hunting clumped patches of shareable food – inter-group hostilityReciprocity and Cooperation among Kin and Non-kin-What about cooperation among nonrelatives?-Reciprocity
oYou scratch my back and I’ll scratch yours. oInvolves cooperative behaviour, but cooperation is in the best self-interest of the participant.oEvolutionary approaches to reciprocity have relied heavily on game theory odetermine optimal strategies that depend on what others in the game are doingfrequency-dependent optimalityoPrisoner’s Dilemma o