Evolution and Human Behavior: Evolutionary Psychology

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Evolution and Human Behavior
Evolutionary Psychology Selection shapes behavior
by shaping the underlying organs that produce
it. This is the way selection always
works. Selection improves circulation by shaping
the organs responsible for circulation. Likewise
selection can produce adaptive behavior by
shaping the organs responsible for behavior
e.g., brain, nervous system, endocrine system.
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Evolution and Human Behavior
Evolutionary Psychology There is no mind/body
divide. The mind is (very fancy) meat and
chemistry, just like the rest of us. Cells
differ in what genes are turned on. 2/3 of human
genes are turned on in brain cells ½ of those
(1/3 of all human genes) are turned on only in
brain cells. Selection seems to have been active
in shaping the way brains work.
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Selection designed the cognitive architecture of
the human mind. For example, selection designs
learning mechanisms. Language learning mechanisms
provide a good example Geared for features of
human language (phonemes, syntax,
etc.) Temporally limited to infancy and
childhood.
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Selection designed many specific kinds of
cognitive architecture. gt Language learning
mechanisms wont solve other kinds of
problems. gt And an open-ended learning device
will never learn language. Cognitive
mechanisms (like all adaptations) are
specialized. They are domain-specific and content
dependent. (face recognition) They are designed
to solve problems that were important in the EEA.
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Recap Altruism can evolve either by kin
selection or reciprocity. Reciprocity requires
that BgtC and that actors exchange
roles. Individuals must not be allowed to take
benefits without paying costs. Such individuals
are cheaters. Reciprocity can only persist if
altruists discriminate against cheaters. Of
course, to do so you must recognize a cheater
when you see one? cheater-detection mechanism.
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The Wason Task One of your clerical tasks is to
make sure that documents have been marked
correctly. They must conform to this rule If
document is rated D then it must be marked code
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D
F
3
5
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Youre a bouncer in a bar. You must make sure
your patrons conform to this rule If a person is
drinking beer he must be over 21 years old.
beer
soda
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Variables in the Wason Task Familiar vs.
unfamiliar little effect Abstract vs. concrete
little effect Descriptive rule vs. possibility of
cheating BIG effect.
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Evolved cognitive mechanisms should not be
culturally variable. They should be human
universals. Another example Incest
avoidance. Why is inbreeding (incest)
bad? Increases the chance of harmful recessive
genes being expressed (occurring in the
homozygous condition).
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Rr
RR
Rr
Rr
rr

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Cultural preferences and norms about marriage
partners are variable. But people generally dont
marry their close relatives (royalty the
conspicuous exception). Why not? Evolved
cognitive mechanisms discourage it. People are
apparently not very sexually attracted to those
they grow up with.
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• Evidence
• Minor marriage in china.
• lower fertility and higher divorce rates, both
  related in a dose-dependent way to early
  exposure.

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Figure 18.05
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Evidence 1. Minor marriage in china. 2. Lebanese
parallel cousin marriage lower fertility and
higher divorce rates than other types of cousin
marriages.
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Figure 18.06
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Evidence 1. Minor marriage in china. 2. Lebanese
parallel cousin marriage 3. Kibbutz age
mates very unlikely to marry (14 out of 2769)
and in all these case one partner joined after
the age of 6.
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The workings of the human mind seem to be
specialized for particular fitness-relevant
tasks. Selection must be the architect.
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