Presentation on theme: "Becoming Human: Evolution of pair-bonding Social systems of our primate relatives: 1.Old world monkeys: Female bonded groups 2.Gibbons: monogamy 3.Orangutans:"— Presentation transcript:
Becoming Human: Evolution of pair-bonding Social systems of our primate relatives: 1.Old world monkeys: Female bonded groups 2.Gibbons: monogamy 3.Orangutans: exploded harems 4.Gorillas: true harems 5.Chimpanzees, bonobos: multi- male/female groups, male-bonded groups
Early hominins A. ramidus (Ardi) low sexual dimorphism mybp; A. afarensis (Lucy) 3.3 mybp high sexual dimorphism Australopiths are generally assumed to have had high male-male competition; harems, single male – female bonded groups
Homo erectus: grade shift Increasingly dependent offspring Lower sexual dimorphism (increase in female body size especially) Larger, more cooperative social groups Evolutionary dilemma – creating cooperative muliti-male/female breeding groups with high paternal investment (which requires paternal certainty) Canine model? High pa, but exclusive breeding Primate model? Multiple breeding, but low pa
Sexual selection: Hand axes over brawn? Hand axe as sign of male quality? Symmetry; appreciation of beauty; resourcefulness; artistic skill? Unused hand axes – practice; display? Male domestication? Beginning of the meat for sex deal? Cooperative hunting among Homo heidelbergensis First spears 400,000 ybp (Schoningen, Germany)
Neanderthals: Sexual division of labor? Some archaeological evidence suggests less sexual division of labor among Neanderthals (lack of tailoring artifacts; robustness of female bodies). Less division – more fragile social system? Clear division of labor in traditional human societies.
Sex role specialization Kuhn & Stiner (2006): Neanderthal remains provide no evidence of womens work. Neanderthal diet almost exclusively big game, no significant small game or vegetable matter No evidence of bone needles or awls indicating tailored clothing No matter how one chooses to interpret the ethnographic record, it is impossible to argue that Neandertal females and juveniles were fulfilling the same roles … as females and juveniles in recent hunter-gatherer groups (Kuhn & Stiner, 2006, p. 958).
Sexual Economics: Sex if the price is right for women (not men) Parental investment theory: Sex for women should be viewed as rare and valuable with important benefits (resources, long-term commitment, etc.). Not so for men (less investing sex). Females, not males, generally react negatively to explicit sexual images (cheapens sex). But female reactions to explicit sexual images are more positive if paired with expensive, rather than cheap product
Sex differences in Jealousy Hypothesis: If a major concern of males is paternity certainty and major concern of females is securing resources, then emotions may have evolved to protect this interests. Males more jealous of sexual infidelity; female more jealous of emotional infidelity Please think of a serious committed romantic relationship that you have had in the past, that you currently have, or that you would like to have. Imagine that you discover that the person with whom you've been seriously involved became interested in someone else. What would distress or upset you more (please circle only one): (A) Imagining your partner forming a deep emotional attachment to that person. (B) Imagining your partner enjoying passionate sexual intercourse with that other person. (p. 252) Controversy over forced choice method; stronger effects for males than females Recent review (Saragin et al, 2012) supports theory, but more needed on actual infidelity
Promiscuous vs. committed mating strategies: Shaping the social context More religious/politically conservative = greater opposition to recreational drugs More secular/politically liberal = acceptance of recreational drugs Why does anyone care about others use of recreational drugs? Ans: drugs connected to promiscuity; promiscuity connected to mating strategy Committed mating strategy threatened by promiscuity; philandering mating strategy aided by promiscuity