Transcript Introduction to Evolution

Introduction to Psychology
Suzy Scherf
Lecture 2: How Did We Get Here?
Critiquing the SSSM
Evolution, Heredity, and Behavior
What is Psychology Like w/o Evolution?
1.
2.
3.
4.
5.
What is Psychology Like w/o Evolution?
6. It presumes that learning operates by a very small
number of general-purpose mechanisms.
What is Psychology Like w/o Evolution?
6. It presumes that learning operates by a very small
number of general-purpose mechanisms.
• Some things we are overprepared to learn
• Other things we are underprepared to learn
What is Psychology Like w/o Evolution?
7. It underestimates the biological constraints on
behavior.
What is Psychology Like w/o Evolution?
7. It underestimates the biological constraints on
behavior.
• Universal People – Donald Brown (1991)
• Universal Characteristics:
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.
Psychology with Evolution
1. It has a basic understanding of what the mind is for.
Psychology with Evolution
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
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:
Debunking Myths about Evolution
Myth:
GREAT CHAIN OF BEING
GOD
Highest complexity
Angels
Humans
Apes
Plants
Rocks
Lowest complexity
Debunking Myths about Evolution
Truth:
Today
Humans
Chimps Monkeys Clams
E. Coli
Cousins
Twigs = Extinct Species
Beginning
Debunking Myths about Evolution
Truth:
Debunking Myths about Evolution
2. Humans are the ultimate goal of evolution.
Myth:
Truth:
Debunking Myths about Evolution
• 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
• 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?
1.
2.
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.
Natural Selection - Filter Analogy
Individuals in Current Generation
Environmental
Barriers to
Reproduction
And Survival
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 generations
human 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):
1.
2.
Sexual Selection
• Sexual selection favors traits that help increase the
# of matings in the fast sex:
1.
2.
Sexual Selection
• Sexual selection favors traits that help increase the
quality of matings in the slow sex:
1.
2.
Sexual Selection
• When males = females reproductive rate (lots of
birds):
1.
2.
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.