Transcript Psych 110

Part 2
Nature
Evolution, language, and
species-typical (innate) behavior
patterns
© Kip Smith, 2003
Outline of the course
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Foundations
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The science of mind and behavior
Nature
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How evolution has shaped mind and behavior
Species-typical behavior patterns
Examples:
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Sticklebacks
Language
Later: Nurture, (Ab)Normal minds
© Kip Smith, 2003
Today
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Evolution, what it is, how it works
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Random variation, genes
Natural selection
Sexual selection
Its implications for psychology
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Some of our behavior patterns are innate
They have been shaped by millions of years of
adaptation to our environmental niche
© Kip Smith, 2003
Next
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The curious behavior patterns of the
stickleback
Curious behavior patterns of humans
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Mate selection
Casual sex
Jealousy
Aggression
Altruism
© Kip Smith, 2003
Next +
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Language, a uniquely human behavior
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Syntax
Semantics
Evidence for the innate nature of
language & for Chomsky’s generative
grammar
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Children and the emergence of creole
The language developed by the deaf children
of Nicaragua
© Kip Smith, 2003
Schedule
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Wenzday Jan 29
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2.1 Evolution
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Friday Jan 31
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2.2 Curious behavior
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Monday Feb 3
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Muddiest point
2.3 Language
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Study guide
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Wenzday Feb 5
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Review
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Friday Feb 7
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Test
© Kip Smith, 2003
2.1 How evolution has shaped
mind and behavior
© Kip Smith, 2003
An Evolution Primer
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Evolution has three components
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Random Variation
Natural Selection
Sexual Selection
Your textbook, like most books since
Victorian times, discusses only the first
two
© Kip Smith, 2003
1 Random variation
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Variation is the engine of diversity
Sexual reproduction
&
Genetic mutation
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Produce minute, random genetic
differences
© Kip Smith, 2003
Minute, random genetic
differences
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Make you different than your parents
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Accumulate to make different species
© Kip Smith, 2003
Genes
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Biochemical units of heredity
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Segments of chromosomes, of DNA
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Humans have 46 chromosomes
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23 from mother, 23 from father
Everything about genes and how they do what they do is
more appropriately discussed in biology class.
© Kip Smith, 2003
Minute random changes
in genetic code
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If the variation does not harm or interfere with
the organism’s ability to fit its niche, the
organism has the opportunity to mate and pass
those genes on to the next generation
Most variations are not helpful
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They are unlikely to survive and be passed on
Some are monstrous and are spontaneously aborted
© Kip Smith, 2003
Random
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Evolutionary
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vs.
Has no direction
Has no purpose
Has no moral status or
implications
Does not care
Evolution happens
© Kip Smith, 2003
Directed
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Teleological change
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Has a purpose
Has a goal
Examples
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Goal-directed behavior
Moral training
Evolution is NOT directed
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The random nature of genetic variation has
significant implications that some people find
unsettling:
We humans are NOT the pinnacle of creation
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We just happen to be the way we are
If the world were to have another go at it, human may
not have evolved
Bats have a much better claim to the pinnacle
than humans
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They FIT their niche perfectly
© Kip Smith, 2003
Myth 1
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“Evolution says that humans are descended from
monkeys”
Humans, apes, and monkeys have a common
ancestor
Random variation has made us different than
that ancestor and each other
© Kip Smith, 2003
2 Natural selection
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Natural selection eliminates species that
fail to match their niche
Natural selection winnows random
variations that do not FIT
Fitness refers to the organism’s match to
its ecological niche
Fit = the organism's match to its
ecological niche
© Kip Smith, 2003
Fit is the match to a niche
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If a species fits its niche, it is likely to
survive
Natural selection and fit IS all about
the survival of the survivors
It is NOT about the survival of the fittest,
the healthiest, the smartest, or the most
beautiful
© Kip Smith, 2003
Natural selection
works at the species level
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Utterly impersonal
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If you don’t fit your niche, you die
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If your species doesn’t fit its niche, you go
extinct
Those who survive are likely to breed and
pass their genes to the next generation
© Kip Smith, 2003
Nature and evolution are
impersonal
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If your environment changes and your
species does not adapt, you go extinct
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Large dinosaurs
Mammoths
Whales?
Beatles
© Kip Smith, 2003
The role of the environment
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The environment provides the niche
The species has to adapt to it
Random variation is the engine of
adaptation
Natural selection gauges the fit
© Kip Smith, 2003
The human niche
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The human niche is hunter-gatherer /
predatory nomad / prey
Humans evolved to solve the problems
faced by a predatory species that was
easy prey on the Pleistocene African
savanna
© Kip Smith, 2003
Our adaptation
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We evolved as we did to fit the huntergatherer niche
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Bipedal
Eyes forward
We are social
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We form groups for protection and the
exchange of goods and services
© Kip Smith, 2003
Our adaptation
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We can eat almost everything
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Three kinds of teeth
We store fat to help us survive lean times
We crave salt and sugar
We grew big brains
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Why?
© Kip Smith, 2003
Our quandary
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We are biologically & genetically prepared
for hunting & gathering, for a predatory,
nomadic life style
We are adapted for a niche that no longer
exists
We have changed our environment and
we don’t fit it
© Kip Smith, 2003
3 Sexual Selection
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In most mammalian species, including
humans, females choose which male they
will mate with
Males develop sexual displays to attract
and retain females
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The peacock’s tail
The stag’s horns
…
© Kip Smith, 2003
Sexual displays
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Are ‘expensive’
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Are an indicator of the male’s fitness
© Kip Smith, 2003
Sexual selection works at the
individual level
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The peacock with a fine fine superfine tail
is advertising his fitness to all the peahens
Every peahen knows it is wiser to mate
with a fit peacock than with an unfit
peacock
© Kip Smith, 2003
Puritanical censorship
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Victorian male chauvinist scientists had a
real problem with Darwin’s theory of
sexual selection
Females choosing males?
Totally scandalous !
© Kip Smith, 2003
Bi-directional sexual selection
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Darwin suggested that in some species,
including humans, sexual selection works
both ways
Females choose the males with the best
displays
Males choose the females with the best
displays
© Kip Smith, 2003
For next time
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Read
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Scientific American
article 1:
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Timbergen, N. (1952).
The curious behavior of
the stickleback
Chapters 1, 2, 3
© Kip Smith, 2003