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 ModelFamilial Benefits ModelConditions 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 TheoryRegarding 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 Pinkerhttp://video.google.com/videoplay?docid=3554279466299738997&q=siblings+%2B+evolutionary+psychology&hl=en

Origin of Kinship Altruism

Reciprocity demands familiarityin ancient times, familiarity meant

kinshipkinship altruism = manifestation of

reciprocal altruismHow 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 normalnepotism 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 areKinship 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 valueHughes (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 daysrecipient of reward changed with each

exerciselength of time subjects were prepared to

endure pain proportional to genetic relatedness of recipient

Life-or-Death Helpingstudy 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 Helpingstudy 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?

having kin in close proximity during life-or-death situations affects survival rates Mayflower and Donner party

Kitty Genovese

SiblingsParent-offspring conflictSibling conflictsiblings can be strong social

allies, but also represent competition for parental resources clip: “In Her Shoes”

adaptive problem for siblings clip: “Narnia”

SiblingsSulloway, 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 =.25Two generations of paternity uncertaintyorder 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 Selectionstudy by Littlefield & Rushton (1986)

Examined magnitude of grief when a child dies loss of inclusive fitness prospects

Self-reported measures of griefParents grieved more than distant

relativesage and health of childdifferences in grandparents’ grief

Final Discussion Topics

Altruism as an explanation for creationism? http://video.google.com/videoplay?docid=665607106454961127&q=a

ltruism (10:12)

What about social justice?What about adoption?