© Kip Smith, 2003

Part 2

Nature

Evolution, language, and species-typical (innate) behavior patterns

© Kip Smith, 2003

Outline of the course

Foundations The science of mind and behavior

Nature How evolution has shaped mind and behavior Species-typical behavior patterns Examples:

Sticklebacks Language

Later: Nurture, (Ab)Normal minds

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Today

Evolution, what it is, how it works Random variation, genes Natural selection Sexual selection

Its implications for psychology Some of our behavior patterns are innate They have been shaped by millions of years of

adaptation to our environmental niche

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Next

The curious behavior patterns of the stickleback

Curious behavior patterns of humans Mate selection Casual sex Jealousy Aggression Altruism

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Next +

Language, a uniquely human behavior Syntax Semantics

Evidence for the innate nature of language & for Chomsky’s generative grammar

Children and the emergence of creole The language developed by the deaf children

of Nicaragua

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Schedule

Wenzday Jan 29

Friday Jan 31

Monday Feb 3

Wenzday Feb 5

Friday Feb 7

2.1 Evolution

2.2 Curious behavior Muddiest point

2.3 Language Study guide

Review

Test

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2.1 How evolution has shaped mind and behavior

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An Evolution Primer

Evolution has three components Random Variation Natural Selection Sexual Selection

Your textbook, like most books since Victorian times, discusses only the first two

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1 Random variation

Variation is the engine of diversity

Sexual reproduction&

Genetic mutation

Produce minute, random genetic differences

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Minute, random genetic differences

Make you different than your parents

Accumulate to make different species

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Genes

Biochemical units of heredity

Segments of chromosomes, of DNA

Humans have 46 chromosomes 23 from mother, 23 from father

Everything about genes and how they do what they do is more appropriately discussed in biology class.

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Minute random changesin genetic code

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 They are unlikely to survive and be passed on Some are monstrous and are spontaneously aborted

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Random vs. Directed

Evolutionary Has no direction Has no purpose Has no moral status or

implications Does not care

Evolution happens

Teleological change Has a purpose Has a goal

Examples Goal-directed behavior Moral training

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Evolution is NOT directed

The random nature of genetic variation has significant implications that some people find unsettling:

We humans are NOT the pinnacle of creation 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

They FIT their niche perfectly

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Myth 1

“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

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2 Natural selection

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

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Fit is the match to a niche

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

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Natural selection works at the species level

Utterly impersonal

If you don’t fit your niche, you die

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

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Nature and evolution are impersonal

If your environment changes and your species does not adapt, you go extinct

Large dinosaurs Mammoths Whales? Beatles

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The role of the environment

The environment provides the niche The species has to adapt to it Random variation is the engine of

adaptation Natural selection gauges the fit

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The human niche

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

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Our adaptation

We evolved as we did to fit the hunter-gatherer niche

Bipedal Eyes forward

We are social We form groups for protection and the

exchange of goods and services

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Our adaptation

We can eat almost everything Three kinds of teeth We store fat to help us survive lean times We crave salt and sugar

We grew big brains Why?

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Our quandary

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

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3 Sexual Selection

In most mammalian species, including humans, females choose which male they will mate with

Males develop sexual displays to attract and retain females

The peacock’s tail The stag’s horns …

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Sexual displays

Are ‘expensive’

Are an indicator of the male’s fitness

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Sexual selection works at the individual level

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

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Puritanical censorship

Victorian male chauvinist scientists had a real problem with Darwin’s theory of sexual selection

Females choosing males? Totally scandalous !

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Bi-directional sexual selection

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

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For next time

Read

Scientific American article 1:

Timbergen, N. (1952). The curious behavior of the stickleback

Chapters 1, 2, 3