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PSYC 3420 Lecture Notes - Menopause, Cortisol, Kin Recognition

Course Code
PSYC 3420
Irwin Silverman

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Chapter 8: Problems of kinship
Theory and implications of inclusive fitness
- Hamilton’s rule: is that natural selection favours mechanisms for altruism when c < rb
- c is the cost to the actor
- r is the degree of genetic relatedness between the actor and the recipient
- b is the benefit to the recipient
- The key is that Hamilton’s rule defines the conditions under which adaptations for aid to kin can evolve. It
defines the selection pressure to which genes for altruism
- Only those genes that code for traits that fulfill Hamilton’s rule can spread throughout the population and
hence evolve to become part of the species typical repertoire. This is sometimes called evolvability
constraint because only genes that meet the conditions of Hamilton’s rule can evolve
- The theory of inclusive fitness renders parenting as a special case of kinship, albeit an extremely important
special case, because parenting represents just one way of investing in vehicles that contain copies of one’s
- Other specific relationships that would have recurred throughout human evolutionary history include
sibships, half sibships, grandparenthood, grandchildhood, and so on
- Sibships; one consequence is that siblings historically faced the recurrent adaptive problem of competing
with each other for access to parental resources
- Birth order affects the niches a person selects, firstborns being more likely to feel solidarity with parents
and perceive them as dependable, whereas middle borns appear more likely to invest in bonds outside of
the family
- Middle borns must always share their parents’ investments, because there is never a time when other
siblings are not around, perhaps accounting for why middle borns are less identified with their families
- Another aspect of kinship that is theoretically critical is whether a sib is a full or a half sib
- Grandparents are related to their grandchildren by an r of .25
- The fact that modern women often live well beyond menopause has led to the hypothesis that menopause
itself evolved as a means of ceasing direct reproduction to invest in children and then grandchildren, in
what has become known as the grandmother hypothesis
- Hypotheses about universal aspects of kinship;
- 1. Suggest that ego-centered kin terminology will be universal, in all societies all kin will be classified in
reference to a focal individual. Ex. My parents are not the same people as your parents
- 2. All kinship systems will make critical distinctions along the lines of sex. Ex. Mothers are distinguished
from fathers
- 3. Generation is also critical. Children become increasingly valuable vehicles for their parents, whereas
parents become less and less useful to their children
- 4. Kin relationships will be universally arrayed on a dimension of closeness, and closeness will be highly
linked with genetic relatedness. Ex. The emotional and cultural aspect
- 5. The degree of cooperation and solidarity between kin will be a function of their degree of genetic
relatedness. People are predicted to turn to close kin rather than distant kin when it really matters
- 6. The elder members of an extended kin family will encourage the younger members to behave more
altruistically and cooperatively toward collateral kin
- 7. One’s position within an extended kin network will be core components of the self-concept. Your beliefs
about who you are will include kin linkages
- 8. Despite differences across cultures in the exact kin terms that are employed and their putative meanings,
people everywhere will be aware who their real relatives are
- 9. Kinship terms will be used to persuade and influence other people, even when no actual kinship is
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