Transcript HumanBehavior2_post

How does sexual selection influence human mate choice?
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6/25/08: The Evolution of Human Behavior: Mate Choice
Lecture objective:
Generate adaptive hypotheses and predictions
about human mate choice
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Caveats to studying human behavior
from an evolutionary perspective:
1. Humans do not consciously do things to increase
their inclusive fitness. (Neither do non-human
animals.) Those organisms that tended to behave in
a way that maximized their fitness tended to leave
more offspring who also behaved that way.
2. Saying a behavior is adaptive does not mean it is
morally/ethically right.
3. Saying a behavior is adaptive does not mean it is
genetically determined/developmentally inflexible.
4. Not all human behavior is adaptive in modern
society. However, it could have been adaptive for
our ancestors in the recent past (EEA).
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Darwin recognized that some individuals have
a reproductive advantage over others
Sexual selection:
a form of natural selection that occurs
when individuals vary in their ability to obtain mates
relative to others of the same sex
What generally limits the reproductive success of females?
What generally limits the reproductive success of males?
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In pre-industrial humans, polygyny was the norm
Frequency of marriage types
across cultures (pre-industrial)
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Choosiness in women vs. men
Hypothesis: In humans,
females are the
Prediction: Women should be
Prediction: Women should have
But in general, both men and women appear
to be choosy when seeking a long term mate.
Why might this be?
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Adaptive mate preferences in humans
Based on your knowledge of sexual selection, if humans
show adaptive preferences for mate qualities, then:
Men should generally prefer women
who exhibit signs of
Women should generally prefer men
who exhibit signs of
and
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What men look for in women:
fertility (beauty, youthfulness)
Hypothesis: The (stereotypical)
male preference for the female
hourglass figure is adaptive
Prediction: Women with an hourglass figure
should be
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What men look for in women:
fertility (beauty, youthfulness)
In 37 cultures (out of 37 studied),
males prefer mates _____________
Hypothesis: Male preference for
younger females is adaptive
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What men look for in women:
fertility (beauty, youthfulness)
The quality of nuptial gifts often
correlates with aspects of mate quality
Hypothesis: The amount of resources
invested in an engagement ring is adaptive
Prediction: Males should buy more expensive
engagement rings for _________________
____________________________
typically received a more expensive ring
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Importance of female attractiveness is no myth…
Prediction: Male preference for attractive females
should be culturally universal
In folk tales, female protagonists were typically:
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What women look for in men: wealth
Women advertise for _________
Arizona
Higher income increases a male’s
___________________
(NPC = number of potential conceptions)
India
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What women look for in men: health
Women generally prefer men with features that:
___________________
(higher levels of testosterone)
Low T
Med. T
High T
_____________________
(better developmental stability)
Normal
Asymm.
Perfect Sym.
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What women look for in men: health
Women generally prefer men with a masculine facial structure,
which is linked with high levels of testosterone
Prediction: If this preference is adaptive, women in the _________ of their cycle
should be more likely to prefer men with a masculine facial structure
Why?
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What women look for in men: health
In Jamaica (compared to Britian), parasite load is higher,
medical care is less common, and paternal care is more rare
Prediction: If women’s preferences for male facial structure
is adaptively linked to health, then ________ women should
prefer more masculinized faces than _________ women
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(Thankfully), beauty is in the eye of the beholder
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Do humans have cryptic female choice?
What is the function of female orgasm (FO)?
Non-adaptive hypothesis: FO is an
__________________________
Adaptive hypothesis: FO is an adaptive means by which females can
manipulate the ___________________________
Prediction: Women with more
symmetrical mates will be more likely to
have copulations that are
accompanied by FO
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Are female preferences
for male body odor adaptive?
Products of the MHC (major histocompatibility complex)
play an important role in immune function
The “smelly
t-shirt”
experiment
Prediction: Non-pregnant women
should prefer the body odor of
men who are genetically
_____________________
Why might this occur?
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Is social “copying” of mate judgments adaptive?
Prediction: Female choice should promote
_________ attitudes (by women) toward men
who other women find attractive (hunk)
Prediction: Within-sex competition should
promote __________ attitudes (by men) toward
men who women find attractive (jealousy)
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