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Who are you? Write down the first 10 descriptions of yourself that come to mind. Try to work as quickly as possible. Problems of Kinship Emily Polachek What is Family? Defining Family Emlen (1995) described two types of families: simple families & extended families both of these definitions hinge on the presence of a reproducing female What about homosexual couples? Only 3% of all bird and mammalian families live in family groups living with families is detrimental to reproduction The Evolution of Families Ecological Constraints Model Familial Benefits Model Conditions necessary for the evolution of families: more offspring than reproductive vacancies offspring must wait for reproductive vacancies until they have the required attributes to compete for mating positions benefits of staying with the family must be large Predictions of Emlen’s Theory Regarding kinship and cooperation shortage of reproductive vacancies more resources, more stable families more assistance in child-rearing in families sexual aggression is low Regarding changes associated with the elimination of a breeder conflict concerning the appointment of a successor breeder who is not genetically related will increase sexual aggression clip: Steven Pinker http://video.google.com/videoplay?docid=3554279466299738997&q=siblings+%2B+evolutionary+psychology&hl=en Origin of Kinship Altruism Reciprocity demands familiarity in ancient times, familiarity meant kinship kinship altruism = manifestation of reciprocal altruism How far-reaching are the effects? Inuits = strongest non-kin relationship < weakest kin relationship understanding among non-kin Studying Kinship Families are more difficult to study than strangers extended families don’t live near one another favoring kin seems normal nepotism challenges Western principles Inclusive Fitness Theory An individual’s own reproductive success plus the reproductive success of relatives as weighed by the degree of genetic relatedness Altruism - a behavior that results in costs to the self and benefits another Hamilton’s Rule: c < rb c = cost to individual r = degree of genetic relatedness b = benefit to other person Genetic Relatedness Identical twin = 100% Sibling = 50% Parent = 50% Grandparent = 25% Aunt/Uncle = 25% Cousin = 12.5% Great Aunt/Uncle = 12.5% Great Grandparent =12.5% Hypotheses about Kinship (from Daly, Salmon, & Wilson, 1997) Ego-cetered kin terminology Distinctions regarding sex Distinctions regarding generation “Closeness” associated with genetic relatedness Hypotheses about Kinship (from Daly, Salmon, & Wilson, 1997) Elder members will encourage altruism towards collateral kin clip: “Gilmore Girls” Position within kin network becomes a part of self-concept People know who their “real” kin are Kinship terms produce illusory feeling of connectedness between unrelated people Alarm Calling in Squirrels Alerted squirrels benefit, but the alarm caller is in trouble potential explanations: predator confusion hypothesis predator deterrance hypothesis reciprocal altruism parental investment inclusive fitness hypthesis can these findings be applies to humans? http://www.agpix.com/catalog/AGPix_Read/ large/AGPix_Read_0041_Lg.jpg Helping in Humans A study of 300 women in Los Angeles more likely to help closely related kin more likely to help those with greater reproductive value Hughes (1988) used mathematical analysis to show that key individuals in a society are those who have just passed through puberty now able to reproduce Helping in Humans Fieldman et al. (submitted) asked subjects to sit in isometric position for cash reward performed on successive days recipient of reward changed with each exercise length of time subjects were prepared to endure pain proportional to genetic relatedness of recipient Life-or-Death Helping study by Burnstein et al. (1994) Two types of helping: substantial helping trivial helping Two scenarios: burning house and must save one person inside run errands for someone Life-or-Death Helping study by Burnstein et al. (1994) Helping decreased as genetic relatedness decreased especially strong effect in life-or-death scenario Helping in life-or-death scenario decreased with age effects of age reversed in trivial scenario Helping is a function of genetic relatedness and age Why were one-year-olds helped the most? Life-or-Death Helping Clip: “The Pretender” Expansion on Burnstein et al. (1994) measure of emotional closeness more likely to be emotionally close with more related kin emotional closeness correlated with altruistic behavior Are these constructs really as different as Buss makes them out to be? Kitty Genovese having kin in close proximity during life-or-death situations affects survival rates Mayflower and Donner party Siblings Parent-offspring conflict Sibling conflict siblings can be strong social allies, but also represent competition for parental resources clip: “In Her Shoes” adaptive problem for siblings clip: “Narnia” Siblings Sulloway, 1996 In all societies, parents discriminate among their children Adaptive problems create niches based on birth order oldest child: support the status quo middle child: continually trying to surpass older children youngest child: most likely to be spoiled clip: “Narnia” Siblings (from Sulloway, 1996) Strategies siblings use to procure parental resources promote parental favor directly dominate their rivals counter domination How does this relate to your experiences with siblings? Patterns of Inheritance Three predictions: genetically related kin & spouses closely related offspring rather than siblings study of 1000 randomly selected decendents in British Columbia recorded dollar value of estates labeled beneficiaries by genetic relatedness + “spouse” and “nonfamily” Patterns of Inheritance Women distribute wealth to more people men leave everything to their spouse women did not trust men to distribute wealth older men remarry more often than older women may divert wealth from decedent to new offspring rather than shared offsrping older women are usually postmenopausal 92.3% wealth to spouses or family 46% to relatives sharing 50% genes 8% to relatives sharing 25% genes less than 1% to 12.5% of genes Four times as much to offspring than siblings Investment by Grandparents Genetic relatedness =.25 Two generations of paternity uncertainty order of investment: Mother’s mother Mother’s father Father’s mother Father’s father clip: “Gilmore Girls” Investment by Grandparents Discriminative grandparental investment theory DeKay (1995) confirmed hypotheses Euler & Weitzel (1996) results confirmed hypotheses MoFa being higher rules out sex differences ruled out differences due to proximity Grief: A Measure of Selection study by Littlefield & Rushton (1986) Examined magnitude of grief when a child dies loss of inclusive fitness prospects Self-reported measures of grief Parents grieved more than distant relatives age and health of child differences in grandparents’ grief Final Discussion Topics Altruism as an explanation for creationism? http://video.google.com/videoplay?docid=665607106454961127&q=altruism (10:12) What about social justice? What about adoption?
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