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Ch 3 - Life History Theory.docx

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PSYC 208
Paul Wehr

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Life History Theory 10/1/2012 10:22:00 AM Life History Theory  Shift from mating to parenting  Paternal uncertainty: not sure that it’s their offspring  Women don’t need to overinvest in men because they do not gain more offspring from mating with more men Primate Life-Histories  Greater encephalization  longer the life-span & longer the individual portions of the life- span  Life-span o Gestation: development before birth o Infancy: early development after birth o Juvenile periods: rapid development, but not as rapid as infancy o Adulthood o Post-reproduction  Humans live past reproduction after menopause  Why do organisms die?  Why such along post-reproductive period? o When you stop being reproductive, you have to live long enough to raise your last offspring, even if it’s at 50 Fertility & Reproductive Value  Fertility: likelihood that copulation will lead to a viable pregnancy (peaks at 25)  Reproductive Value: average number of future offspring an individual can have (peaks during late teens in women) r vs. K Strategies  r = rate of increase with no resource limitations o Environment allows for rapid growth o r-strategist produces many offspring o Insects (relative to vertebrates)  Produce offspring, don’t invest in them, so most of them die  K = carrying capacity for a habitat with resources limitations o Environment usually at carrying capacity o K-strategist produces quality offspring o Vertebrates (relative to insects) Life-history Differences  r-strategist o Many offspring o Ow parental investment o High infant mortality o Short life-span o Rapid development to reproductive state o Early reproduction o Small body size o Variable population size  Catastrophic mortality  Recolonization of vacated areas  Boom  vast starvation  K-strategist o Fewer offspring o High parental investment o Low infant mortality o Long life-span o Slow development o Delayed reproduction o Large body size o Stable population size  Constant mortality rate  Consistent habitat Rodent & Plant Examples  r-strategist o Voles  Transient habitats  3 week gestation  Large litters  Early reproduction o Dandelions  Catastrophic environment  Rapid lifecycle with early intense reproduction  K-strategist o Squirrels  Forest & prairies with constant production  6 weeks gestation  Smaller litters  Develop slower  Breed year after birth o Trees  Forests near K  Invest in foliage Humans are Extreme K-strategists  Ancestral environment was at carrying capacity  Invest heavily in offspring o 9 months gestation o Lactation  Typically produce 1 child per birth  Low infant mortality rate  80 year life-span  14-16 years to reach sexual maturity o Unlike squirrels, which are r-strategists compared to humans  Starting to act like voles, expand population rapidly, then catastrophic death Attachment  Attachment: psychological adaptation connecting the infant with mother  John Bowlby: English psychoanalyst: attachment enhanced survival and social learning  Maternal deprivation in Rhesus Monkeys: o Raised in social isolation: aggression and socially incompetent (out of fear) o Unable to provide maternal care as adults  Separation Anxiety: emotional distress observed in infants when separated from primary caregiver o Appears 6-8 months: peaks at 14-18 months o Fear of strangers  Imprinting (Konrad Lorenz) o Baby ducklings imprint on first large moving objects  follow that o If mom’s too far away, we might get eaten Attachment Styles  Mary Ainsworth: The Strange Situation o Experiment  Parent and infant are introduced to the experimental rom  Parent and infant are alone. Parent does not participate while infant explores  Stranger enters, converses with parent, then approaches infant; parent leaves inconspicuously  First separation episode: stranger’s behavior directed towards infant  First reunion episode: parent greets and comforts infant, then leaves again  Second separation episode: infant is alone  Continuation of second separation episode: stranger enters  Second reunion episode: parent enters, greets infant, and picks up infant; stranger leaves inconspicuously o Secure attachment  Explore comfortably: upset when mother leaves; calms quickly when she returns o Anxious/ambivalent attachment  Explores but anxious; protests when mother leaves; difficult to console when she returns o Avoidant attachment  Explores comfortably; unconcerned when mother leaves  Should cry when alone because you’re vulnerable  Disorganized attachment (added later) o Simultaneous avoidance and contact seeking or “freezing” o Child is afraid of its caregiver  Insecure attachment can interact with genes to produce psychopathology Senescence  Simultaneous deterioration of all biological systems due to old age o Why does life end?  Selection should favor strategies that sacrifice reproduction in the far future for reproduction in the far future for reproduction in the present (e.g. testosterone) o Early reproduction = more reproduction o Mortality rate is high over long periods o Therefore, concentrate reproduction early in life! o Selection is stronger for mutations expressed in young individuals and weaker for mutations expressed later in life.  Selection for pleiotropic genes that increase reproduction early but lead to death later  Genes are beneficial if beneficial effects outweigh the negative ones  Negative effects of genes show up later on in life, the good genes are concentrated in early life  have kids early Bereavement  Acute reaction to death of someone biologically important (6-12 months) o Grief increases o Mental and physical health deteriorates o Mortality rate increases (people tend to die more)  Asymmetry in grief reactions o Life history  Men have stronger reactions to loss of spouse  Women have stronger rea
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