Lecture 7 - Kin Recognition: Cues to Kinship
why learn to discriminate Kin?
-target altruism towards them
-avoid harming them too much (or too often)
-avoid mating with close kin (likely to carry deleterious recessive genes: really bad
for you if you get two of the same deleterious genes.
-cues tap into some kinship estimator, gives us a kinship index.
-kinship index monitors and downgrades sexual attraction towards close kin
-regulates altruistic behaviour
-potential proximate mechanisms: aversion and/or complete sexual non-attraction,
genuine concern for their well-being
Cues of Kinship
-situational predictors (e.g, who did i grow up with?)
-phenotype matching to self or other relatives?
-visual recognition, resemblance?
-odor? : can recognize mothers odor
-behavioural similarity (gesture, personality quirks?) : similarity in siblings
-other sensory modalities (e.g. voice) : learn voice
-nominal cues : last names
Early Childhood Association
-statistical predictor of siblinghood (in many species with parental care)
-proposed by Westermarck (1891) as mechanism for incest avoidance: people are
not sexually attracted to those whom they grow up with from childhood
-contrast to other views that incest is only prevented by taboos
aside: evade. that taboos not wholly responsible for incest avoidance:
-non-human animals also avoid mating with siblings
-cultures with explicit taboos
aside: parent/offspring and sibling mating is particularly detrimental, cousins
not so much
Predictions of the Westermarck Hypothesis -childrens raised together will be averse to mating with each other as adults - even
if they are actually unrelated
-sub-prediction: if forced together, such unions have:
-sexual intercourse among actual siblings will be negatively associated with
association during childhood
-children growing up with opposite-sex children will show greater moral aversion to
incest than those not so raised
Unrelated Children Together: Israel Kibbutzim
-communal settlements in Israel, religious or secular
-children raised communally with age-mates
-sexual interaction between age-mates is not discouraged, perhaps even
-in data from 2769 couples from over 200 kibbutz, not a single couple was raised
together from ages 0-6
-no evidence of sexual intercourse either
-not treating age mates as potential mates (great warmth, not sexual)
-100 years ago in Taiwan, two forms of arranged marriages were common
1. Major marriage: the grooms parents (avg. age 3) paid a brideprice to
bride's parents (avg. age 19), big formal ceremony welcoming bride into groom's family
2. Minor marriage (sim-pua): the bride was "adopted" in infancy by the
groom's parents. Formal marriage ceremony occurred when the girl was about 17 years
-sexual attraction may not be there.
-minor marriages more likely to end in divorce (when raised together as siblings,
more likely to end in divorce)
-more likely to end when the husband was a younger age when the bride was
adopted (more childhood time spent together, more likely to divorce)
-despite social pressure to have babies
-people express distaste for minor marriages -fewer offspring in minor marriages than major marriages
-more husbands (48%) visiting "dark rooms" (brothels) in minor marriages. far
fewer in major marriages (14%)
-more husbands (32%) living with a concubine (second woman in house) in minor
marriages. much less (4.3%) in major marriages
-more women (33%) involved in adultery in minor marriages. much less (11.3%) in
-shows that when they are raised together, more likely to get divorced, have
less kids, and commit adultery.
-social status of the marriage
third type of marriage: uxorilocal marriages: men move to their wifes'
household. considered lower status. these men are gen