- Social groups—
(may vary seasonally)
- Multi-male, multi-female:
- Uni-male, multi-female ("Harem"): Hamadryas baboons
- Uni-female, multi-male: some S.A. titis, marmosets
- Two-adult ("nuclear family") group: gibbons; some Atelinae
- Socially dispersed— some lemurs
- Mating:
- Mating systems and parental investment:
- Monogamy (paternity fairly certain, paternal investment high)
- Polygyny
- Polyandry (rare)
- Promiscuity
- Dispersal to other groups— avoids incest
- Mate choice and sexual selection:
- Females generally choosy (predicted by parental investment theory)
- Status and rank
- Sociosexual signals (breasts, testes, genital swelling, mandrill faces)
(compare: odors in non-primates)
- Copulatory posture shown Campbell P.472
- Play and Grooming often precede mating activity
- Extra-pair copulations ("adultery"): paternal uncertainty
- Females may use this to secure male protection (Hrdy)
- Homosexual behavior (not 'tendency'): bonobos as a special case
- Mating and social status:
- Status and rank depend on alliances: male, female differences
- Group size related to more neocortex (remembering more individuals);
females need to remember more than males
- Wrangham's model:
- Defendable food:
- Encourages large groups
- Encourages female bonding and cooperation
- well-defined relationships among females
- protection against infanticide
- males must adjust to this
- Food not defendable:
- Favors smaller groups (unless predation risks are very high, as in baboons)
- Females do not cooperate or bond; loose relationships only
- Males only deal with one female at a time
- Generally higher risk of predation (may limit smallness of groups)
- Thierry's model:
- High predation risk with clumped resources:
- Favors cohesive social groups, philopatry, nepotism
- Scramble-competition:
- Time-limited, so dominance is less important
- Contest-competition:
- Socially limited, so dominance asymmetry is important
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