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Gleitman • Gross • Reisberg
Psychology
EIGHTH EDITION
Chapter 2
The Genetic and Evolutionary
Roots of Behavior
©2011 W. W. Norton & Company, Inc.
Chapter Topics
• Genetics and DNA
• Evolution by Natural Selection
• The Genetics and Evolution of Behavior
• Some Final Thoughts: The Strengths and
the Limits of Evolutionary Theorizing
• Summary
Genetics and DNA
• The nucleus of each biological cell
contains chromosomes, which each
contain a single molecule of DNA.
• Within this molecule, genes govern the
cell’s functioning by providing detailed
instructions for making proteins. This a
very complex process.
Making proteins
The genes contain the information needed
to make proteins. This allows the
information in the gene to be expressed
for the genotype.
A genotype is your complete heritable
genetic identity. This is the “nature”
meaning what you inherit from your
parents.
Genotype and Phenotype
Phenotype: This is the description of your
actual physical characteristics,
temperament, personality, etc. This is
influenced by your genotype and by your
environment.
The phenotype and genotype are in
constant interaction.
Why do we need to know this information
for the study of psychology?
Videos on Genetics
at 23andme
https://youtu.be/ubq4eu_TDFc
https://youtu.be/tJjXpiWKMyA
https://youtu.be/-Yg89GY61DE
https://youtu.be/kLpr6t4-eLI
https://youtu.be/QCm2x9OABI8
Genome
• Humans have 23 pairs of chromosomes
and roughly 25,000 protein-coding genes.
• These are collectively called the person’s
genome.
• A genome is an organism’s complete set
of DNA. It contains all the information
needed to build maintain that organism.
• In humans, a copy of the entire genome is
contained in all cells that have a nucleus.
Gene Expression
• In each cell, some genes are expressed,
or activated in some way, at any point in
time and others are not.
• Gene expression is controlled by the
biochemical environment inside the cell,
which is influenced by the organism’s:
• Overall environment.
• Experiences and Behaviors.
Genetic Coding
https://www.23andme.com/you/ancestry/c
omposition/
Interactions among Genes
• Most characteristics are influenced by the
action of many genes.
• Each gene is paired with another gene.
• The pairs are located at corresponding
positions on pairs of chromosomes.
Allele
Either a pair or a series of alternative
forms of the gene, that come about due to
a mutation of some kind, that are
responsible for hereditary variation.
These DNA codings (proteins) determine
the distinct traits that can be passed from
parents to offspring.
Dominant vs. Recessive
• The genes may or may not be the same
allele.
• Geneticists use the terms dominant and
recessive to describe the inheritance
patterns of certain traits. In other words,
how likely is it for a certain phenotype to
pass from parent to offspring.
• These terms are used to predict the
probability of someone inheriting a
phenotype.
Dominant and Recessive
Organisms have two alleles for each trait.
One allele may be dominant (so it is
expressed) and the other is recessive (so
it is masked).
Co-dominant is when both alleles are
expressed (AB blood type).
Incomplete dominant is when both alleles
mix, as in flowers. This means both traits
are shown and not masked.
Darwin and Evolution
• Charles Darwin hypothesized that all
modern organisms:
• are descended from a small set of shared
ancestors.
• have emerged over time through the process
of evolution.
• An enormous amount of evidence has
confirmed these proposals.
Darwin and Evolution
• The key mechanism is natural selection.
• If individuals with certain traits are more likely
to survive and reproduce,
• their genes will be better represented in the next
generation.
• And if the genes gave rise to the
advantageous traits,
• those traits will be more common in the next
generation.
Naturalistic Fallacy
• It is important to avoid the naturalistic
fallacy, however—it does not follow that
evolution somehow improves organisms or
that anything natural is good.
• This means the genotypes and
phenotypes that are passed on to survive
allow the organisms to survive. It does not
necessarily mean this is good or bad.
• Can you think of examples?
Genetics in Psychology
Heritability refers to a statistic of
proportion to explain how likely we are to
inherit something through our genetics.
The numbers range from 0.0, where we
see that genes do not contribute at all to
phenotypic individual difference or the
overt traits and behaviors, to 1.0 where
genes are the only reason for these
differences.
Genetic Epidemiology of
Selected Mental Health Issues
Prevalence
Paternal
Age onset Mortality
Fertility Heritability
(%)
age effect
0.30
1
2.0
0.05
0.90
1.4
Autism
Anorexia
0.60
nervosa
Schizophre
0.70
nia
Bipolar
affective 1.25
disorder
Unipolar
10.22
depression
Anxiety
28.80
disorders
15
6.2
0.33
0.56
—
22
2.6
0.40
0.81
1.4
25
2.0
0.65
0.85
1.2
32
1.8
0.90
0.37
1
11
1.2
0.90
0.32
—
Molecular Psychiatry (2009) 14, 1072–1082; doi:10.1038/mp.2009.85; published online 25 August 2009
The role of genetic variation in the causation of mental illness: an evolution-informed framework. By R. Uher.
Genetic Predisposition
Prevalence refers to proportion of the
population found to have a condition. This
one is number of cases per 10,000 people.
Incidence means the number of new
cases in a population at a given time.
Heritability versus Prevalence.
What do you believe are the factors
involved that create the illness when
someone has a genetic predisposition?
Outside Forces
ILLNESS
• Anorexia
•
• Autism
•
•
•
•
•
•
Schizophrenia
Bipolar Disorder
Major Depression
Generalized Anxiety
OCD
•
•
•
OTHER CAUSES
Related to being white,
female, and in a Western
Culture.
Diagnosis has increased
with time.
Increased risks living in
urban environment and
being an ethnic minority.
Depression 1 in 10
people.
MTHFR, 1/3 in lifetime.
Mental Health Booster
ILLNESSES
High rates of mortality.
People who experience them also have a
low likelihood of having children.
Biopsychosocial Model
Biological, psychological, and social
factors are all interlinked and important
with regards to causing disease or
promoting health.
What affects the body affects the mind and
vice versa.
Biopsychosocial Model
The Diathesis Stress Model
https://youtu.be/ayWVkmYH6TY
A person’s genetic predisposition,
combined with psychological stressors,
are what cause someone to become ill.
Evolutionary Psychology
Field of Psychology.
The goal with research in this field is to
discover and understand the design of the
human mind.
This is an approach to understanding the
psychology of a person based on the fields
of neuroscience, evolution, and biology.
Notable is the human brain is experienceexpectant and experience-dependent.
Evolutionary Psychology
They define the mind as: a set of
information processing machines designed
by natural selection to solve adaptive
problems faced by our hunter-gatherer
ancestors.
We have natural competencies: see,
speak, find someone beautiful, reciprocate
a favor, fall in love, fear disease, initiate an
attack, moral outrage, navigate, etc.
Evolutionary Psychology
These natural competencies are only
possible due to the brain having increasing
capacities to initiate, support, and
regulate, these activities.
“Instinct Blindness”: These are automatic.
https://youtu.be/xbRCFuet0Nk
Mate selection, aggression, gender
behavior, emotions, the way our brain
works, etc.
Evolution and Aggression
2.2 million people in the USA are
incarcerated. This is the most of any
nation.
1 in 31 Americans under DOC custody.
 1 in 3 Americans has a criminal record.
Of the 2.2 million, about one half are drug
offenses (unknown what kind of drug).
Genetics and Behavior
• Evolution by natural selection has shaped
behaviors just as much as physical traits.
• For human animals it can literally take
thousands of years for the evolutionary
brain to catch up with the environment
changes due to lifestyles and technology.
• Even though one brain, or a part of a brain
changes, does not mean the societal
evolutionary instincts within all brains have
changed.
Crows and Tools
New Caledonian Crows, in the Pacific
Island of New Caledonia, use tools. They
will evolve in their problem solving and the
tools they make.
Organisms obviously have evolved
mechanisms so they can alter responses ,
problem solve and learn new skills.
https://youtu.be/cbSu2PXOTOc
Genetics and Intelligence
• An individual’s level of intelligence is
influenced by genetic factors.
• OR is it?
• Identical twins are a good example: their
levels of intelligence are similar, even if they
grew up separately.
• Can intelliegence be increased? YES!
Heritability Ratio
• Intelligence is also influenced by
environmental factors.
• heritability = genetic variance ∕ total
phenotypic variance
• The heritability ratio is a summary of the effect
of genetic differences within a given
population and environment.
Heritability Ratio
• The value of the heritability ratio depends
on the group being examined.
• In groups with lower socioeconomic status
(SES), the heritability may be zero.
• Heritability also increases with a person’s age.
• This may be because people choose environments
that amplify their genetic potential.
IQ and Natural Selection
• Human intelligence was favored by natural
selection.
• Our ancestors had a reproductive advantage
if they could communicate, solve problems,
and draw conclusions
• Why do humans vary in their intelligence?
• It’s unclear—not all inherited characteristics
are the direct result of natural selection.
Naturalistic Fallacy
Remember Naturalistic Fallacy?
How would you apply this to the term
“intelligence”?
What does the term “intelligence” really
mean?
http://bigthink.com/videos/howardgardner-on-the-eight-intelligences
Evolution and Infidelity
• An evolutionary perspective also leads to
the expectation that men will be more
distressed by sexual infidelity in their
partners than by emotional infidelity, which
indeed is reported.
• Women should show the reverse pattern,
as is also reported.
Concept Quiz
1) Most of an organism’s traits are not controlled
by a single gene, but rather are influenced by a
large number of gene pairs. This pattern is
called:
a) gene dominance.
b) genotype.
c) polygenic inheritance.
d) natural selection.
Concept Quiz
2) An evolutionary perspective on jealousy
predicts that males will be more upset by their
partner’s _________________ than females
will be.
a)
b)
c)
d)
imagined infidelity
emotional infidelity
sexual infidelity
serial infidelity
Video Clips
This concludes the presentation
slides for Chapter 2
For more learning resources, visit the StudySpace at
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