Introduction to PsychologySuzy Scherf

Lecture 2: How Did We Get Here?

Critiquing the SSSMEvolution, Heredity, and Behavior

What is Psychology Like w/o Evolution?

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5.

6. It presumes that learning operates by a very small number of general-purpose mechanisms.

What is Psychology Like w/o Evolution?

• Some things we are overprepared to learn

• Other things we are underprepared to learn

6. It presumes that learning operates by a very small number of general-purpose mechanisms.

What is Psychology Like w/o Evolution?

7. It underestimates the biological constraints on behavior.

What is Psychology Like w/o Evolution?

• Universal People – Donald Brown (1991)

• Universal Characteristics:

7. It underestimates the biological constraints on behavior.

What is Psychology Like w/o Evolution?

8. It assumes that the psychologists’ job is to discover how culture and experience produce variation in human behavior.

What is Psychology Like w/o Evolution?

Psychology with Evolution

1. It has a basic understanding of what the mind is for.

2. Psychologists can ask questions about why the mind exists in terms of its designed function

Psychology with Evolution

3. Research findings across sub-disciplines make more sense

Psychology with Evolution

Debunking Myths about Evolution

1. Evolution doesn’t make sense because there is no fossil record that shows how humans came from chimps!

Myth:

Truth:

Myth:

GREAT CHAIN OF BEING

Angels

Humans

Apes

Plants

GOD

Rocks Lowest complexity

Highest complexity

Debunking Myths about Evolution

Truth:

Beginning

TodayChimps Monkeys Clams E. Coli

Twigs = Extinct Species

Humans

Cousins

Debunking Myths about Evolution

Truth:

Debunking Myths about Evolution

2. Humans are the ultimate goal of evolution.

Myth:

Debunking Myths about Evolution

Truth:

• Who thinks we are “higher” than a virus?

Debunking Myths about Evolution

3. Step-children are more likely to be abused, so it must be “natural.”

Myth:

Truth:

Debunking Myths about Evolution

3. Naturalistic Fallacy

Debunking Myths about Evolution

•Herbert Spencer - Social Darwinism

“The poverty of the incapable, the distresses that come upon the imprudent, the starvation of the idle, and those shoulderings aside of the weak by the strong…are the decrees of a large, farseeing benevolence.”

The Theory of Evolution

• What does the theory explain?

• How does evolution influence change in biological organisms?

What does the Theory of Evolution Explain?

What does the Theory of Evolution Explain?

What does the Theory of Evolution Explain?

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Evolution via Natural Selection

How does it Work?

What is Natural Selection?

• Natural Selection is a filter that weeds out those who get to pass on their traits from those that don’t.

• Eventually, traits that get passed down become more common and individuals are better able to deal with current environmental challenges.

EnvironmentalBarriers to

ReproductionAnd Survival

Natural Selection - Filter AnalogyIndividuals in Current Generation

Natural Selection is Survival of the Fittest, Right?

Natural Selection is Survival of the Fittest, Right?

Natural Selection is ...

Frigate Bird Galapagos Penguins Beach lizards

Evolution via Natural Selection

• Selection can only choose from existing alternatives

• Evolution is cumulative -

• Traits spread b/c they yield a net profit in reproductive success

What does Natural Selection Produce?

What are Adaptations?

• Natural Selection is always designing organisms for the sole purpose of reproduction.

• Adaptations are

• Adaptations are

What are Adaptations?

• Natural Selection can design any traits that contribute to reproduction.

• Including:

How do We Recognize Adaptations?

1. Structural complexity (many parts) -

2. Designed for a particular function -

3. Specialized for a narrow function -

Types of Adaptations

• Obligate adaptations -

• Including:

Types of Adaptations

• Facultative adaptations -

• Including:

Psychological Adaptations

• Specialized mental organs (modules) each:

• Including:

Psychological Adaptations

• Remember - natural selection cannot design behavior itself

• Natural selection designs

• Psychological organs -

Out-of-Date Adaptations

• Evolution measured in generationshuman generation ≈bacteria generation ≈

• So, human evolution

• If local environments change faster than does a generation -

Out-of-Date Adaptations

Example: Use this thinking to try and understand why most of our ancestors were never overweight, but many of us are overweight now.

Are All Traits Adaptations?

Is the nose an adaptation for holding

up glasses?

A Special Kind of Selection:Sexual Selection

What’s up with the elaborate feathers?

Sexual Selection

• Traits spread b/c they lead to more offspring than they cost.

• What about traits like the peacock feathers that make an organism more vulnerable to predators?

Sexual Selection: The Peacock

Come on Mamma.I got what you need!

Sexual Selection

• Often acts unevenly in the two sexes because of differences in reproductive rate.

• Reproductive Rate =

Fast rate =

Slow rate =

Sexual Selection

• When males > females reproductive rate (most mammals):

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Sexual Selection

• Sexual selection favors traits that help increase the # of matings in the fast sex:

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Sexual Selection

• Sexual selection favors traits that help increase the quality of matings in the slow sex:

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Sexual Selection

• When males = females reproductive rate (lots of birds):

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Sexual Selection

What would you expect the sex differences to be like in a species in which male ≈ female reproductive rate?

Sexual Selection

Predict the reproductive rates in this species.

Sexual Selection

Predict the reproductive rates in this species.