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Chapter 3-4

PSYC 208 Chapter 3-4: Chapter 3 & 4 - Life History Theory

9 Pages
29 Views
Summer 2012

Department
Psychology
Course Code
PSYC 208
Professor
Paul Wehr
Chapter
3-4

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Chapter 3 – Life History Theory 16:03
Life History Theory
-Species-typical solutions for reproductive or survival problems.
-Somatic efforts vs. Reproductive efforts
Somatic: Growth and development (ex. Getting bigger, stronger, smarter)
Reproductive: Divert resources used for somatic efforts to reproduction
oMating efforts: Finding mates and reproducing
oParenting efforts: Rearing offspring
oAsexual organisms may invest only in mating efforts (reproducing offspring is
already parenting)
Humans first invest in somatic efforts for first 14-16 years, then reproductive.
Sex Differences in Investment
-Women invest more in parenting (they have larger obligatory investment than men)
-Men are more biased towards mating efforts. Two possible explanations:
Paternal Uncertainty – Can never be sure, therefore less beneficial to invest
Opportunity costs in reproductive opportunities – Could make other babies
Primate Life Histories
-As advancement of primate increases, time during infancy increases.
-Adolescence does not exist in other primate species, only humans.
-Humans don’t become fully reproductive until 20-ish. Many important decisions are then made later.
-Lemur (18), Macaque (25), Gibbon (30), Chimpanzee (45)
-Human have post-reproductive period (post-menopause period lasts 30 years). Why?
Textbook: Post-menopausal women are positively selected because they can provide
resources for grandchildren, and improve reproductive fitness of those share their genes!
Fertility vs. Reproductive Value
-Fertility: likelihood that copulation will result in pregnancy. (Peak is 25 in women)
-Reproductive Value: average number of future offspring one can have at any given time.
Peaks in late-teen in women
Increases from birth, peaks at 20, then decreases
Decreases because you can only have that many kids in your lifetime, eventually you’ll stop
-Due to lack of menopause, men’s reproductive value will never reach zero.
r Strategies vs. K Strategies
-Species-typical reproductive strategies
r Strategists K Strategists
-Many offspring
-Low parental investment
-High infant mortality rate
-Short lifespan
-Rapid development
-Early reproduction
-Small body size
-Switch early from somatic
-Variable population size
-Few offspring
-High parental investment
-Low infant mortality rate
-Long lifespan
-Slow development
-Delayed reproduction
-Large body size
-Wait to switch
-Stable population size
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-r strategists
Reproduce as many as possible because there’s no environmental limitations
Quality of offspring doesn’t matter much
Variable population size: population “spikes” over and over again
Voles: have transient habitats, early reproduction
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-K strategists
Carrying capacity for a habitat with resource limitations
Focuses on quality of offspring
Trees: forests are near carrying capacity most of the time, energy is spent to spread foliage
-K and r are comparative terms, can be k when compared to one species but r to another
-Humans are extremely k-strategists
Indicates that ancestral environment was at carrying capacity
Attachment
-Emotional bond between infant and caregiver
-Internal working model: Developing representations of caregiver by infants, determine they way they
explore environments, etc.
-Bowlby
Attachment enhances reproductive success and survival
Babies are programmed to be cute and attract adult attention, adults are programmed to take
care of them too
-Separation Anxiety
Appears at 6-8 months, peaks at 14-18 months
Stranger anxiety appears too
-Attachment styles (Mary Ainsworth)
Secure Attachment: upset when mother leaves, calms quickly when returns
Anxious Attachment: anxious when mother’s present, protests when leaves (often have
caregivers that are inconsistent with their behaviours)
Avoidant Attachment: unconcerned either way (often have caregivers that are dismissing)
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Description
Chapter 3 – Life History Theory 16:03 Life History Theory - Species-typical solutions for reproductive or survival problems. - Somatic efforts vs. Reproductive efforts  Somatic: Growth and development (ex. Getting bigger, stronger, smarter)  Reproductive: Divert resources used for somatic efforts to reproduction o Mating efforts: Finding mates and reproducing o Parenting efforts: Rearing offspring o Asexual organisms may invest only in mating efforts (reproducing offspring is already parenting) Humans first invest in somatic efforts for first 14-16 years, then reproductive. Sex Differences in Investment - Women invest more in parenting (they have larger obligatory investment than men) - Men are more biased towards mating efforts. Two possible explanations:  Paternal Uncertainty – Can never be sure, therefore less beneficial to invest  Opportunity costs in reproductive opportunities – Could make other babies Primate Life Histories - As advancement of primate increases, time during infancy increases. - Adolescence does not exist in other primate species, only humans. - Humans don’t become fully reproductive until 20-ish. Many important decisions are then made later. - Lemur (18), Macaque (25), Gibbon (30), Chimpanzee (45) - Human have post-reproductive period (post-menopause period lasts 30 years). Why?  Textbook: Post-menopausal women are positively selected because they can provide resources for grandchildren, and improve reproductive fitness of those share their genes! Fertility vs. Reproductive Value - Fertility: likelihood that copulation will result in pregnancy. (Peak is 25 in women) - Reproductive Value: average number of future offspring one can have at any given time.  Peaks in late-teen in women  Increases from birth, peaks at 20, then decreases  Decreases because you can only have that many kids in your lifetime, eventually you’ll stop - Due to lack of menopause, men’s reproductive value will never reach zero. r Strategies vs. K Strategies - Species-typical reproductive strategies r Strategists K Strategists - Many offspring - Few offspring - Low parental investment - High parental investment - High infant mortality rate - Low infant mortality rate - Short lifespan - Long lifespan - Rapid development - Slow development - Early reproduction - Delayed reproduction - Small body size - Large body size - Switch early from somatic - Wait to switch - Variable population size - Stable population size - r strategists  Reproduce as many as possible because there’s no environmental limitations  Quality of offspring doesn’t matter much  Variable population size: population “spikes” over and over again  Voles: have transient habitats, early reproduction - K strategists  Carrying capacity for a habitat with resource limitations  Focuses on quality of offspring  Trees: forests are near carrying capacity most of the time, energy is spent to spread foliage - K and r are comparative terms, can be k when compared to one species but r to another - Humans are extremely k-strategists  Indicates that ancestral environment was at carrying capacity Attachment - Emotional bond between infant and caregiver - Internal working model: Developing representations of caregiver by infants, determine they way they explore environments, etc. - Bowlby  Attachment enhances reproductive success and survival  Babies are programmed to be cute and attract adult attention, adults are programmed to take care of them too - Separation Anxiety  Appears at 6-8 months, peaks at 14-18 months  Stranger anxiety appears too - Attachment styles (Mary Ainsworth)  Secure Attachment: upset when mother leaves, calms quickly when returns  Anxious Attachment: anxious when mother’s present, protests when leaves (often have caregivers that are inconsistent with their behaviours)  Avoidant Attachment: unconcerned either way (often have caregivers that are dismissing)  Disorganized Attachment: Simultaneous avoidance and contact seeking; confused; child is afraid of caregiver (often because of abuse) Senescence - Progression towards death; simultaneous deterioration of all biological functions - Why does it happen?  Selection should favour strategies that sacrifice possibility of reproduction in the future for reproduction right now - Mutations that help reproduction in the short run may harm us in the long run - Traits that help us increase early reproduction get passed on more  Testosterone helps men reproduce earlier, but wears out male physiology in the long run, and can lead to deficiencies in immune system Mortality Rate in Lifespan vs. Reproduction - Relatively high in childhood, decreases during reproduction, then increase again. - Reproduction shoots up at the end of adolescence, then decreases over time. - More reproductive effort is concentrated in adulthood (when mortality rate is lowest) Bereavement - Acute reaction to death of someone biologically important - Lasts about 6-12 months - Involves grief, mental and physical health risks, and mortality rate increases (“Broken heart syndrome”) - Sexual asymmetry in bereavement  Men have stronger reaction to loss of spouse, women loss of offspring o Men invest more in spouse, loss of spouse = loss of more investment  Stronger reaction to loss of younger spouse and older offspring o Younger spouse and older offspring have higher reproductive values Afterthought - Foetal programming – prenatal environment prepares the foetus for postnatal conditions. - Prenatal environment affects babies a
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