PSYC 3100 Lecture Notes - Lecture 15: Alloparenting, Grandmother Hypothesis, Infant Mortality
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Outline Lecture 15 Parenting 1
1. Child-rearing in pre-modern societies
-conflicts of interest between parent and offspring because they are not genetically
–genes make tough decisions in face of tough circumstances. Could stop investing in
an offspring if the genes are faulty.
–Somatic effort: genes investment in self, making sure body is sufficiently large
enough to survive, immune system, etc.
–Reproductive effort: things we need to do to attract mates, as well as parental
investment (investment in one offspring that takes awat from parents' ability to invest
in other offspring, including investing in future offspring)
–“Cooperative breeding”: much help from other relatives
–“it takes a village to raise a child”: many people help to care for child (grandparents)
–in agricultural society: for children 0-4, taken from obsevations of all 342 members of
“Grande Anse” trinidad.
–-mother holds most of the time (almost half)
–but another half of the time other people are holding the child other than the
–Why does father care less than mother? (holds 10% of time): parental uncertainty:
there is always possibility that some other male has impregnated his woman.
Selects for decreased investment because of uncertainty.
–Trade-offs revisited: parental effort vs. mating effort
–Hadza hunter gatherers: men play with their children less when there are more single
fertile women around. They could be courting whether openly or not.
–what about grandmothers? They invest less in grandoffspring.
–Why experience menopause and stop reproducing?:
–women have long post-reproductive lifespan: why?
–Could be limited number of eggs
–shorter lifespan in EEA (environment of evolutionary adaptiveness: lifespan in
ancestral environments was lower, much infant fatalities
2. Grandmother Hypothesis: older women can increase RS by switching to investing in
-children without mothers experience high mortality, & maternal mortality
increases with age
-grandmothers increase grandchild survival by increasing mother's survival and
by direct grandmothering
-this can result in:
-decreased infant mortality
-decreased interbirth intervals
-earlier age of first reproduction
-evidence for grandmother hypothesis:
-grandmothers increased the fecundity (number of offspring) and lifetime
reproductive success (LRS) of their daughters (18th century data)
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