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Cooperative Alliances. Baboons. Alliances based on reciprocity, grooming Baboons who recently gave help most likely to get help Males who don’t form alliances rarely get access to females Females who were recently groomed more likely to help groomer. Chimpanzees.
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Baboons • Alliances based on reciprocity, grooming • Baboons who recently gave help most likely to get help • Males who don’t form alliances rarely get access to females • Females who were recently groomed more likely to help groomer
Chimpanzees • Males form alliances to fight alpha male and get access to females • Females shift allegiance to dominant male • Alliances enforced by violence, followed by friendliness • Males bolster alliances with females by grooming her and being friendly to her infants
Needed cognitive capacities • Recognize many individuals • Remember history of interactions with different individuals • Communicate one’s values/needs to others • Perceive values/needs of others • Represent costs & benefits independent of items exchanged
Three bases for alliances • Hamilton’s kin selection • Reciprocity • Becoming indispensable
Banker’s Paradox • Limited amount of capital to loan • People with most money are best credit risk, people with least are worst risk • For helping in general: those in greatest need may be least able to repay us in future, unless problems just temporary • Becoming indispensable increases loyalty of friendship; a way out of paradox
How to be Indispensable • Promote a reputation for unique & exceptional attributes • Recognize personal attributes others value but have difficulty getting from other people • Develop special talents/skills • Seek out those who strongly value your skills & attributes • Avoid groups where your skills not valued • Drive off rivals who offer benefits that you alone formerly provided
Limited Niches for Friendship • Everyone has limited time, energy, effort • Helping one person decreases resources for helping another • How to choose?
Tooby & Cosmides: how we choose friends • Number of slots already filled • Who emits positive externalities (people who have beneficial side effects, such as strength, status, connections) • Select friends who are good at reading your mind (they can understand your needs, etc.) • Select friends who consider you irreplaceable • Select friends who want the same things you want
Costs & Benefits of Friendship:study by Bleske & Buss • Possible short-term sexual access: more often considered by males than females • Provide protection: more often considered by females than males • Provide information about the opposite sex: receive more info & more useful info from same-sex friends than opposite-sex friends • Potential cost: intrasexual rivalry: more often reported by males than females (related to short-term sexual access, perhaps)