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READ the introduction below before you read
the chapter in the text.
Chapter 3 focuses on the impact of genetics and evolutionary adaptation on behavior. Adaptation is a
means of accommodating to changed circumstances.
(Evolution is just one level on which adaptation occurs; another is learning, which will be considered
in Chapter 4.)
Genes, the biological units of heredity, affect our
anatomy and physiology and, through these, affect
our behavioral characteristics. They have their effects
solely by governing the manufacture of the body’s
many different protein molecules. Genes always
work in interaction with environmental influences.
This chapter explains how genetic information is
passed down from one generation to the next
through sexual reproduction. Such concepts as genetic diversity, genotypes and phenotypes, and dominant and recessive genes are explained.
In some cases, a single gene can affect a particular aspect of behavior or cause genetic disorders that
have behavioral consequences. But most differences
among individuals stem from the combined effects
of many genes in interaction with the environment.
We call these polygenic characteristics. Polygenic
characteristics vary in degree from one individual to
another—that is, each individual will have more or
less of the characteristic. In contrast, in the case of
single-gene differences, individuals differ in type
rather than degree.
The mechanism by which evolutionary adaptation takes place is natural selection, a concept originated by Charles Darwin. Darwin argued that inheritable changes that enhance the chances of survival
and reproduction tend to be passed on to the next
generation while inheritable changes that hinder survival or reproductive chances are lost. In other words,
those genes that thwart survival or reproduction are
less likely to be passed on to future generations and
chapter 3
Genetic and Evolutionary
Foundations of Behavior
thus become rarer or disappear. In current evolutionary thinking, Darwin’s critical insights are combined
with a modern understanding of genes.
People have long engaged in selective breeding—reproducing plants and animals in such a way
that desirable traits are developed, enhanced, or continued. Evolution depends on natural selection, defined above, in which the demands of life in a particular environment determine what is a “desirable
trait.” Genetic diversity provides the raw material for
natural selection, but environmental change propels
the process. It is important to recognize that evolution does not involve foresight, since common misconceptions about evolution stem from this erroneous assumption.
Functionalism, which emphasizes the purposes of
behavior, is well suited to an evolutionary viewpoint.
However, not all characteristics that emerge through
evolution should be assumed to be useful.
The chapter next explores instinctual or speciestypical behaviors, such as speaking in humans or
dam-building in beavers. Although biological preparedness is the foundation for such behaviors,
learning can be involved in—even critical to—their
development. Cross-species comparisons of speciestypical behaviors are enlightening. Two types of
comparisons—homology and analogy—are used in
trying to understand the evolutionary development
and functions of behaviors.
One major focus of the evolutionary perspective
has been sexual behavior. Robert Trivers, for example,
has suggested that the relative parental investments required of males and females of a given species will
strongly affect the mating patterns seen in that species.
Thinking in evolutionary terms has also helped us understand aggression, including the greater aggressiveness of male primates as compared with females of
their species. Helping behavior in humans and other
species can be explained as consistent with natural selection, as well. The chapter also describes fallacies in
evolutionary thinking that we should avoid.
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
Notice that there are focus questions in the margins of
the text for your use in studying the material. The following chart lists which Study Guide questions relate to
which focus questions.
Focus Questions
Study Guide Questions
Review of Basic Genetic Mechanisms
1–2
1–6
3
7–9
4–5
11–18
6–7
19–23
Inheritance of Behavioral Traits
8
1–4
9
4
10
5–8
11
9
12
10
13–14
11–13
Evolution by Natural Selection
15
1
16
2–4
17
5–7
18
8
Natural Selection as a Foundation for
Functionalism
19
1–2
20
3–5
21
6
Natural Selection as a Foundation for
Understanding Species-Typical Behaviors
22–23
1–3
24
4
25
5
26
6
27–28
7–9
29
10–12
30
13
Evolutionary Analyses of Mating Patterns
31
2–3
32
4
33
5–6
34
7–9
35
10
36
11–12
37
13
38
14–16
Evolutionary Analyses of Hunting and
Helping
41
1–6
42–43
7–8
The Integrated Study Workout
COMPLETE one section at a time.
Introduction AND Review of Basic Genetic
Mechanisms (pages 51–57)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
How can a microscopic physical thing like a gene
affect something psychological such as verbal ability?
How are genes passed down from parents to children?
How is the environment related to genetic influences
on behavior?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
In the mid-nineteenth century, Charles Darwin offered
a theory of evolution that explained the basis for both
similarities and differences among animal species.
Evolution is a long-term adaptive process.
1. Define adaptation.
Amazingly, Darwin’s theory preceded our understanding of genes but a knowledge of genes adds immeasurably to our understanding of evolution. Genes
are the basic building blocks of heredity. If we want
to understand the genetic contribution and evolutionary forces that shape behavior, we must understand
how genes exert their effects and how they are transmitted from one generation to the next.
2. Do genes affect behavior directly? Explain.
3. Genes affect physical development by directing
the synthesis of
molecules.
The structure of every cell in the body is made
Chapter 3
up of
proteins, and
proteins called
control the
rate of chemical reactions in the cells.
Each protein molecule consists of a sequence of
hundreds or thousands of
(of which there are
distinct
varieties). Physically, genes are segments of long
molecules of
.
4. Define each of the following.
a. genes (Hint: Provide an older and a newer definition.)
Genetic and Evolutionary Foundations of Behavior
27
6. How are genes thought to play a part in long-term
behavioral changes resulting from experience?
Give a specific example.
7. The same genotype can produce different phenotypes.
The set of genes that the
individual inherits
The observable properties
of the body and behavioral traits.
b. coding genes
It is useful to understand how genetic material is
passed down from parents to offspring in sexual reproduction.
8. Strands of DNA are arranged in each cell in
.
structures called
c. regulatory genes
d. “junk DNA”
It is very important to understand that the effects of
genes are always interwoven with the effects of the environment. Neither one alone can affect the biology or
the behavior of an individual.
5. In the context of this chapter, what does environment mean?
9. How many pairs of chromosomes are in a normal
human cell (except an egg or sperm cell)?
10. One pair of chromosomes are sex chromosomes.
How do the sex chromosomes of males and females differ?
Cells can divide in two ways. One type of cell division
is mitosis, the other, meiosis. An understanding of
meiosis is important for understanding the hereditary
transmission of genetic information and the way that
genetic diversity comes about.
11. What is the purpose of mitosis? How is the genetic
material in one resulting cell related to the genetic
material in the other resulting cell?
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
12. Since the cells in all parts of your body (excluding
egg and sperm cells) have the same gene content,
how can the cells end up being so different from
one another—cells in your stomach lining versus
cells in your brain, for example?
13. Meiosis is the type of cell division that produces
or
cells. Through the
exchange of genetic material and subsequent
, several genetically
different egg or sperm cells are formed. The
number of chromosomes in each egg or sperm
cell produced is
.
In human sexual reproduction, the egg and sperm cells
unite, combining their genetic information.
14. The union of an egg and a sperm produces a
single new cell called a(n)
,
which contains 23
of
chromosomes. This new cell then grows through
the process of
.
Each of these new cells is genetically
.
15. Explain the evolutionary advantage of reproducing sexually as opposed to asexually.
We often talk about chromosomes in terms of pairs. In
the case of humans, we usually say there are 23 pairs
of chromosomes, not 46 chromosomes, although both
are true. The pairing is emphasized because it has important consequences. It is not only the chromosomes
that are paired but also the genes they carry. (Hint:
Look at Figure 3.5 on text page 57.)
17. Different genes that could potentially occupy the
same locus on a pair of chromosomes are called
.
18. If the two genes paired at a given locus are
identical, the individual is
at that locus and if the genes are different, the
individual is
at that locus.
19. What does it mean to say an allele is dominant? to
say an allele is recessive? Are all gene pairs either
dominant or recessive? Explain.
20. In each of the following cases, assume that there
is an allele M which is dominant and an allele m
which is recessive. Indicate which allele (M or m)
will be expressed in the phenotype for each case.
a. The individual is heterozygous.
b. The individual is homozygous for M.
c. The individual is homozygous for m.
16. Identify the two types of twins, giving two names
for each type. How are the twins genetically related in each type?
Gregor Mendel is famous for his elegant studies of genetics in peas. Mendel’s work, done in the nineteenth
century, still offers a clear picture of certain hereditary
patterns and gave rise to the notion of paired units of
heredity and dominance just discussed.
21. In one experiment, Mendel studied wrinkled-seed
peas and round-seed peas. Explain Mendel’s
breeding procedure.
Chapter 3
22. Why did all of the F1 generation have round seeds?
23. Why did three-fourths of the F2 generation have
round seeds and the other one-fourth wrinkled
seeds? (Hint: Look at Figure 3.6 on text page 57.)
Genetic and Evolutionary Foundations of Behavior
29
2. When dogs of the two breeds were crossbred, how
did the resulting (F1) offspring behave in the same
fear test?
3. When dogs of the F1 generation were mated, what
did the researchers observe with respect to the offspring’s fearfulness? What conclusion was supported regarding the genetic basis of this type of
behavior in cockers and basenjis.
Inheritance of Behavioral Traits (pages 58–63)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
4. Do these results indicate that fear in dogs is controlled by a single gene locus? that environment is
irrelevant to the matter of fear in cockers and
basenjis? Support your answer.
What clues lead scientists to believe that differences
among individuals on some specific trait are due to a
single gene or to many genes?
Can a single gene affect more than one aspect of development or functioning?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
In some cases, a behavioral trait is controlled by a single gene locus and inherited in a Mendelian pattern.
Scott and Fuller revealed just such a pattern in the behavior of two dog breeds—cocker spaniels and basenjis. Specifically, they showed that a particular behavioral trait was controlled by a single gene locus with
one allele dominant over another. (Hint: See Figures
3.7 and 3.8 on text pages 58 and 59.)
1. How did purebred cocker and basenji puppies react when approached by a human who was a
stranger to them?
A Mendelian pattern of inheritance is also found to underlie a specific language disorder in the KE family.
5. Describe the specific language disorder found primarily in the KE family.
6. What does the pattern of inheritance for this disorder suggest about its genetic basis? Specifically,
is the abnormal gene dominant or recessive?
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
7. What does the normal gene do that the abnormal
gene fails to do?
8. Is the normal human version of the gene unique
to humans? Explain the significance of this fact.
Some people have more friends than others. Some people sleep longer on average than others. Some people
learn musical skills more easily than others. Most of
the differences among individuals reflect the combined influences of many genes (in interaction with the
environment, of course), not the effects of single genes.
9. Characteristics affected by many different genes
are called
traits. When we
measure differences among individuals in such
traits, they will differ from one another in
rather than in type. In
other words, individuals will not fall into
distinct
or groups as they
do in the case of single-gene traits. Most often,
the set of scores obtained for polygenic traits
approximates a(n)
distribution. (Hint: Look at Figure 3.10 on text
page 61.)
Selective breeding has been practiced for thousands of
years to produce more desirable strains of plants and
animals. Scientists have used selective breeding to produce strains of animals with specialized behavioral
tendencies.
10. What is the basic approach followed in selective
breeding?
Robert Tryon’s work with “maze bright” and “maze
dull” rats clearly pointed out that even complex behaviors, such as a rat’s ability to learn a maze, can be
powerfully influenced by genetic variation.
11. How did Tryon produce the two strains of rats?
How did he control for the possibility that the rats’
“maze brightness” or “maze dullness” was due to
what they learned from their mothers rather than
to their genes?
12. Why is it important to note that Tryon tested his
subjects only on their ability to learn one particular task?
Psychologists often would like to assess the relative
contributions of genetic and environmental variation
for polygenic behavioral traits in humans.
13. How can such questions be studied in humans?
Evolution by Natural Selection (pages 63–66)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
Since evolution is supposed to involve adaptation,
how does nature “know” which traits will be adaptive
in future generations?
Can individuals inherit traits that their parents have
acquired through experience?
How fast does evolution take place?
Chapter 3
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
The publication of Charles Darwin’s The Origin of
Species in 1859 was a landmark event. It has had
tremendous impact on the way we understand both
biological and psychological issues. Darwin used the
familiar concept of selective breeding—which he
termed artificial selection—as a point of reference. His
major point was that nature, too, involves a kind of selective breeding. He called this natural selection.
1. Explain the concept of natural selection.
Darwin developed his theory without knowing anything about genes. Mendel’s work, a first step toward
understanding genes, was not yet known in the scientific world. Darwin knew only that something existed
that was passed on from one generation to the next
and something that could change, forming the basis
for evolutionary changes in a species.
2. List two sources of the genetic variability that is
the foundation of evolution. Which is the ultimate
source of genetic variation?
Genetic and Evolutionary Foundations of Behavior
31
Evolutionary change is propelled by environmental
change.
5. Specify some aspects of the environment that might
change and thereby lead to evolutionary change?
6. Is evolutionary change always slow and steady?
Support your answer with an example and use the
term observed evolution in your answer.
7. Can complex genetic changes occur as rapidly as
simpler changes? Why or why not?
People sometimes fall into intellectual traps in thinking about evolution. Several related misconceptions
stem from the mistaken assumption that evolution involves foresight.
8. State three specific forms this fundamental misunderstanding can take.
3. What is a mutation? Is it likely to be helpful or
harmful? How does this fit in with natural selection?
a.
b.
c.
4. Explain Lamarck’s notion of the inheritance of acquired characteristics. Is this idea accepted today?
Natural Selection as a Foundation for
Functionalism (pages 67–70)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
Why do newborn infants tightly grasp objects placed
in their hands?
How can we even attempt to discover the reasons for
behaviors that evolved in the very distant past?
Did every characteristic of a species evolve for a particular purpose?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
Psychologists are of course interested in the effects of
evolution on behavior.
1. Briefly explain how the process of natural selection can affect behavior.
4. Are ultimate and proximate explanations of behavior necessarily incompatible? Support your answer.
An ultimate explanation may be plausible, even elegant, and yet be incorrect. We must be careful to insist on scientific evidence in evaluating an explanation.
5. What kinds of evidence can be used to evaluate a
particular ultimate explanation?
We must also realize that a characteristic doesn’t necessarily exist because it is in itself useful.
2. How compatible is the functionalist approach in
psychology with an evolutionary perspective on
behavior?
6. Briefly present four reasons why a given trait or
behavior may not be functional.
a.
Psychologists and biologists who take an evolutionary
perspective distinguish between two kinds of explanations of behavior.
3. Define the terms below.
a. ultimate explanation
b.
c.
d.
b. proximate explanation
Natural Selection as a Foundation for
Understanding Species-Typical Behaviors
(pages 70–78)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
Chapter 3
Are there certain behaviors that seem to mark a dog
as “doggy” or a fish as “fishy” or a person as “human”?
Do facial expressions mean the same thing across different cultures, or does each culture develop its own
code?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
Behavior patterns so characteristic of a species that
they help to identify the species, such as dam building in beavers or speaking in humans, are called instinctive or species-typical behaviors. Human emotional expressions can be regarded as examples of
species-typical behaviors. This idea was advanced by
Darwin and has been supported by recent scientific research.
1. What kind of atlas did Paul Ekman and Wallace
Friesen produce and how did they do it? (Hint: See
Figure 3.14 on text page 71.)
2. Summarize Eibl-Eibesfeldt’s evidence for the universality of the eyebrow flash.
Genetic and Evolutionary Foundations of Behavior
33
4. Comment on the role of learning in the development of species-typical behaviors. Give two examples.
It is the degree of biological preparedness involved in
a behavior that determines whether we call it speciestypical.
5. What is biological preparedness? Illustrate the
concept with either human walking or human talking.
6. Why is it better to treat species-typical behavior as
a relative concept rather than an absolute one?
An important means of better understanding human
traits (or the traits of any given species) is to compare
species. The similarities found can be enlightening.
7. It is important to distinguish two different classes
of cross-species similarities. (Hint: See Figures 3.17
and 3.18 on text page 75.)
3. Does it necessarily follow that a universal nonverbal signal like the eyebrow flash is free of cultural influence? Justify your answer.
is any similarity
a. A(n)
between species that exists because of
convergent evolution.
b. A(n)
is any similarity
between species that exists because of their
common ancestry.
c.
has
taken place when different species
independently evolve a common
characteristic because they have similar
habitats or lifestyles.
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
8. In practice, how can we distinguish between similarities based on homology and those based on
analogy?
Analogies can also provide clues about species-typical
traits.
13. How are analogies useful? What can they not tell
us?
9. What is the particular value of studying homologies?
Evolutionary Analyses of Mating Patterns
(pages 78–84)
Homologies have been useful in understanding the
evolution of smiling, laughing, and other behaviors.
10. Two kinds of human smiles can be differentiated:
Describe them briefly.
11. What is the silent bared-teeth display seen in monkeys and apes? What kind of human smile is it
thought to be related to? What can we learn from
comparing the way this display functions in
macaques and chimpanzees?
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
Is sexual jealousy adaptive?
Why do some species have long-term male-female sexual relationships while others do not?
Can human mating behavior be reasonably explained
in evolutionary terms?
Why are males bigger and stronger than females in
some species and not in others?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
Patterns of mating are an especially interesting area of
study because mating is critical to the survival of any
sexual species and because mating is a fundamental
social behavior.
1. In
12. What is the relaxed open-mouth display seen in
monkeys and apes? What is its apparent meaning?
How is it related to laughing and the happy smile
in humans?
, one male mates with
more than one female. In
,
one female mates with more than one male. In
, one male mates with one
female. In
, members of a group
containing more than one male and more than
one female mate with one another.
Robert Trivers has related various patterns of
courtship and mating behavior to a concept he calls
parental investment.
Chapter 3
Genetic and Evolutionary Foundations of Behavior
35
2. What does Trivers mean by the term parental investment?
6. How do sex differences in the polyandrous species
known as spotted sandpipers support Trivers’s
theory?
3. What general principle relates parental investment
to courtship and mating patterns in Trivers’s theory?
By far the most common mating pattern for birds is
monogamy.
7. What conditions should lead to equal parental investment and thus monogamy?
Polygyny is the most common mating pattern among
mammalian species.
4. According to Trivers, why does high female
parental investment and low male parental investment lead to each of the following?
a. polygyny
b. large size of males
c. high selectivity in the female’s choice of a mate
8. How is equal parental investment related to sex
differences in size and strength?
9. In what kinds of species is monogamy common?
Give specific examples.
10. What evolutionary reasons might underlie the fact
that social monogamy is not always matched by
sexual monogamy?
The primary mating pattern for some species of fish
and birds is polyandry.
5. Why does polyandry make more sense for egglaying species than for mammals?
Chimpanzees and bonobos are among the clearest examples of species that have a polygynandrous mating
pattern.
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Chapter 3
Genetic and Evolutionary Foundations of Behavior
11. What evolutionary advantages might be conferred
by polygynandry in chimpanzees and bonobos?
12. Contrast mating behavior in bonobos with that in
chimpanzees.
16. In evolutionary terms, why might unfaithfulness
occur?
Evolutionary Analyses of Hurting and Helping
(pages 84–90)
CONSIDER these questions before you go on. They are
designed to help you start thinking about this subject, not to
test your knowledge.
Human mating patterns lie somewhere between
monogamy and polygyny. Long-term mating bonds are
the norm everywhere. Where it is legal, polygyny exists,
with some men having two or more wives, but even in
such cultures, most marriages are monogamous.
Do animals help each other or is that an exclusively
human phenomenon?
Why are men generally more violent than women?
13. How does the mix of monogamy and polygyny in
humans fit with Trivers’s theory?
READ this section of your text lightly. Then go back and
read thoroughly, completing the Workout as you proceed.
In the text, aggression refers to fighting and threats of
fighting among members of the same species.
1. Why have brain mechanisms that motivate and organize aggression developed?
In humans, the emotions of romantic love and sexual
jealousy serve important functions.
14. How widespread are these emotions in humans?
What evolutionary purposes do they serve?
2. In mammals (especially primates), how do males
and females differ in terms of aggression? Why
might this be the case?
15. How do humans compare with other species in
terms of love and jealousy?
3. Does this sex difference also apply to humans?
Lust and unfaithfulness also appear to have an evolutionary foundation.
Chapter 3
4. Briefly discuss the exception to the rule found in
Bonobos.
Though members of a given species may fight with one
another even to the point of injury or death, they may
also help one another. Help sometimes takes the form of
cooperation, and at other times appears to be altruistic.
5. Correctly identify each of the following.
a.
occurs when an individual helps another at the expense of its own survival or reproductive capacity.
is any behavior that inb.
creases the survival or reproductive capacity of
another individual.
c.
involves an individual’s
helping another while at the same time helping itself.
6. How does kin selection theory explain the occurrence of apparently altruistic behavior?
7. What evidence supports kin selection theory as it
applies to animals? to humans?
8. How does reciprocity theory explain the occurrence of apparently altruistic behavior?
Genetic and Evolutionary Foundations of Behavior
37
9. Has behavior consistent with reciprocity theory
been observed in the animal world? among humans?
10. In what sense are both theories attempting to redefine altruistic behavior as not really altruistic?
In considering human behavior from an evolutionary
perspective we must be aware of certain fallacies that
can lead to distorted conclusions.
11. What is the naturalistic fallacy? Illustrate your answer with an example of such distorted thinking.
12. What is the deterministic fallacy? Illustrate your
answer with an example of such distorted thinking.
Be sure to READ the Concluding Thoughts at the end of the
chapter. Note important points in your Workout. Then
consolidate your learning by answering the focus questions
in the margins of the text.
After you have studied the chapter thoroughly, CHECK your
understanding with the Self-Test that follows.
38
Chapter 3
Genetic and Evolutionary Foundations of Behavior
Self-Test 1
Multiple-Choice Questions
1. Genes that can occupy the same locus—and can
thus pair with one another—are called:
a. homozygous.
c. alleles.
b. dizygotic.
d. dominant genes.
2. Suppose a person well-informed in the area of genetics refers to “genes for spatial ability.” A correct interpretation of this phrase would be:
a. “genes that directly control a person’s ability
to process spatial information and have no
other function.”
b. “genes that produce a particular anatomy and
physiology, which in turn affect a person’s spatial ability.”
c. “genes that directly control cognitive ability in
general and spatial ability in particular.”
d. that it’s a joke since genes have no effect (direct or indirect) on psychological functioning.
3. Meiosis results in egg and sperm cells containing
number of chromosomes
contained in each of the body’s other cells.
a. exactly the same c. twice the
b. half the
d. four times the
4. The value of sexual—as opposed to asexual—reproduction is the production of offspring that are:
a. genetically diverse.
b. genetically uniform.
c. genetically similar to their parents.
d. numerous.
5. Genes affect both physical development and behavior by directing the synthesis of:
a. DNA.
b. chromosomes.
c. alleles.
d. structural proteins and enzymes.
6. The majority of violence carried out by male primates is related somehow to:
a. protection of offspring.
b. competition for food and water.
c. competition for territory.
d. sex.
7. Any characteristic that varies in a continuous fashion in a population should be presumed:
a. to be polygenic.
b. to be based on a single gene.
c. to involve whole chromosomes rather than individual genes.
d. not to be genetically influenced.
8. Tryon’s attempt to selectively breed “maze bright”
and “maze dull” rats:
a. resulted in failure.
b. showed that only very small differences could
be produced, even over 20 generations.
c. showed that large differences could be produced over several generations.
d. proved that genes are more important than environment in determining intelligence.
9. In the process called natural selection:
a. the breeding of certain domestic animals is
controlled to produce desirable traits in future
generations.
b. inherited traits helpful in overcoming barriers
to survival and reproduction are more likely to
be passed down to offspring.
c. genes that will be helpful in suiting offspring
to future environments are selected for.
d. nature “selects” the traits of the next generation by way of a random shuffle of genes.
10. If chance factors alone cause the gene pools in two
populations of a species to differ, we refer to the
situation as:
a. genetic drift.
c. artificial selection.
b. mutation.
d. a homology.
11. The rate of evolutionary change:
a. is slow and steady.
b. depends primarily on population size.
c. depends on environmental change.
d. was initially rapid but has slowed progressively over the years.
12. John W. believes that male aggression toward
women is controlled by genes and is an unchangeable fact of human nature. His thinking illustrates:
a. reciprocity theory.
b. kin-selection theory.
c. the naturalistic fallacy.
d. the deterministic fallacy.
13. Similarities between species that are due to convergent evolution are called:
a. analogies.
b. homologies.
c. analogies in mammals and homologies in nonmammalian species.
d. homologies in mammals and analogies in nonmammalian species.
14. The ability of premature human infants to support
their weight with the grasp reflex is probably an
example of:
a. the inheritance of acquired characteristics.
b. a vestigial characteristic.
Chapter 3
c. a genetic side effect.
d. reciprocity.
15. According to Robert Trivers, polygyny is related
to
parental investment.
a. high female/low male
b. low female/high male
c. equal male and female
d. no particular pattern of
Essay Questions
16. Discuss the opinions (and where possible, the evidence) offered by Darwin, Ekman and Friesen,
and Eibl-Eibesfeldt regarding the idea that human
emotional expressions are species-typical.
Genetic and Evolutionary Foundations of Behavior
39
Self-Test 2
Multiple-Choice Questions
1. Which of the following is true of polygenic effects?
a. Most measurable differences between people
can be explained in terms of single genes; that
is, they are not polygenic.
b. Without examining the genetic material itself,
there is no way to determine whether a characteristic is polygenic in origin.
c. Polygenic effects are generally brain disorders,
while single-gene effects are positive, useful
traits.
d. The distribution of scores for a polygenic trait
often approximates a normal distribution.
2. The normal human cell (other than egg or sperm
cells) contains
pairs of chromosomes.
a. 12
c. 23
b. 22
d. 46
3. The process by which cells divide for the purpose
of normal body growth is:
a. mitosis.
c. transcription.
b. meiosis.
d. protein synthesis.
17. Does evolution involve foresight? Explain.
4. We can assume that
netically identical.
a. identical twins
b. fraternal twins
c. both identical and fraternal twins
d. no two people
are ge-
5. A friend of yours has brown eyes and her mother
has blue eyes. If blue is recessive and brown is
dominant, you can conclude that your friend:
a. is heterozygous for eye color.
b. is homozygous for eye color.
c. is monozygotic for eye color.
d. is brown-eyed as far as phenotype is concerned, but you can infer nothing about her
genotype.
After you have assessed your understanding on the basis of
Self-Test 1 and have tried to strengthen your preparation in
any areas of weakness, GO ON to Self-Test 2.
6. When Mendel crossed purebred wrinkled-seed
peas with purebred round-seed peas, he found
that all of the F1 generation had round seeds. When
he bred the F1 peas with one another, he found
that:
a. the F2 peas all had round seeds.
b. the F2 peas all had wrinkled seeds.
c. half the F2 peas had round seeds and the other
half had wrinkled seeds.
d. three-fourths of the F2 peas had round seeds
and the other one-fourth had wrinkled seeds.
40
Chapter 3
Genetic and Evolutionary Foundations of Behavior
7. Recent molecular research had led some scientists
to expand the definition of:
a. DNA.
b. genes.
c. amino acids.
d. all of the above.
8. Which of the following is true of mutations?
a. Mutations have little effect on the course of
evolution because they are so rare.
b. Mutations are errors in the replication process;
as such, they inevitably lead to harmful
changes in the structure of DNA.
c. Although mutations usually have harmful consequences, they are sometimes helpful.
d. Mutations are the new collections of genes that
result from the random rearrangement of genes
in sexual reproduction.
9. Which of the following represents a question
posed from a functionalist perspective?
a. At what rate does evolution take place?
b. Which species are most closely related to one
another?
c. What are the possible uses of the human voice?
d. Why do dogs have such a keen sense of smell?
13. A species in which an individual female mates
with several males would be classified as:
a. polygynandrous. c. polygynous.
b. polyandrous.
d. monogamous.
14. Female bonobos dominate males by virtue of their:
a. greater size and strength.
b. greater intelligence.
c. greater speed and agility.
d. strong alliances.
15. When we assume that human genetic biases toward certain behaviors cannot be countered by
learning or culture, we are falling prey to the
fallacy.
a. deterministic
c. naturalistic
b. species-typical
d. genetic dominance
Essay Questions
16. Give evidence of the fact that male primates are
generally more violent than female primates and
discuss it from an evolutionary perspective.
10. The human taste for sugar, which may have several negative health consequences, can be understood as a:
a. vestigial characteristic.
b. genetic side effect.
c. species-typical behavior.
d. result of nutritional deprivation.
11. Birds, some insects, and some mammals can fly.
Similarities among these groups are not due to
common ancestry and would thus represent:
a. homologies.
b. analogies.
c. vestigial characteristics.
d. learning.
12. An ultimate explanation of behavior is an explanation of:
a. the mechanism that actually produces the behavior.
b. the immediate environment conditions that
bring on the behavior.
c. the form a behavior will ultimately take upon
further evolution.
d. why a particular evolutionary development offered an adaptive advantage.
17. How can we explain behavior that appears to be
altruistic? Isn’t such behavior entirely inconsistent
with natural selection?
Chapter 3
Genetic and Evolutionary Foundations of Behavior
41
7. genotype; phenotype
4. a. Sexual reproduction essentially “shuffles the
genetic deck” to produce great diversity in offspring. Diversity offers an evolutionary advantage in that some of the many different types of
individuals created may be capable of adapting
more successfully to changing environmental
conditions and may thus survive and reproduce.
(p. 57)
8. chromosomes
5. d. (p. 53)
9. 23
6. d. (p. 85)
Answers
Introduction and Review of Basic Genetic
Mechanisms
2. protein; structural; enzymes; amino acids; 20; DNA
13. egg; sperm; random; cell divisions; 23
17. alleles
7. a. A polygenic characteristic can often be described in terms of a normal distribution. A singlegene kind of pattern is indicated by step-wise variation. It involves a categorical rather than a graded
difference. (p. 61)
18. homozygous; heterozygous
8. c. (pp. 61–62)
20. a. M, b. M, c. m
9. b. Remember that natural selection acts to produce offspring better suited to the current environment, not some future environment. Natural
selection is driven by success or failure in that current environment. It cannot be affected by an unforeseen future. (p. 64)
14. zygote; pairs; mitosis; unique
Inheritance of Behavioral Traits
9. polygenic; degree; categories; normal
Natural Selection as a Foundation for
Understanding Species-Typical Behaviors
7. a. analogy b. homology c. convergent evolution
10. a. (p. 69)
11. c. (p. 65)
12. d. (p. 89)
Evolutionary Analyses of Mating Patterns
1. polygyny; polyandry; monogamy; polygynandry
Evolutionary Analyses of Hurting and Helping
5. a. Altruism b. Helping c. Cooperation
Self-Test 1
1. c. (p. 57)
2. b. Genes have their effect only by influencing the
manufacture of proteins. In that way, they affect an
individual’s anatomy and physiology. Their effects
on behavior are due to the particular anatomy and
physiology they create and are thus indirect. (p. 55)
3. b. There are 23 pairs of chromosomes in most of
the body’s cells, but only 23 chromosomes in an
egg or sperm cell. When the egg and sperm combine to form the zygote, the full complement of 23
pairs of chromosomes is restored. (p. 55)
13. a. Convergent evolution refers to a situation in
which similarities of environment or lifestyle lead
to similar but independent evolutionary developments. The root of the similarity is not genetic relatedness. In this case, we have an analogy, not a
homology. (p. 75)
14. b. It may help to remember that a vestige is a leftover trace of something from the past. (p. 68)
15. a. (p. 79)
16. Darwin, Ekman and Friesen, and Eibl-Eibesfeldt
have all argued for the idea that we humans are
biologically predisposed to express some emotions in species-typical ways. Ekman and Friesen
developed an atlas of six basic emotional expressions that people exhibit and found widely
differing cultures agreed on what constituted
each of them. Eibl-Eibesfeldt found that certain
nonverbal signals, such as the eyebrow flash,
are universal. He also found that children born
42
Chapter 3
Genetic and Evolutionary Foundations of Behavior
blind nevertheless displayed emotion in the same
way that sighted children do though they could
not have learned to do so through observation.
(p. 71)
17. One of the most common errors people make in
thinking about evolutionary adaptation is to assume
it involves foresight. It does not. Natural selection
operates on the basis of the current environment, not
on the basis of some future environment. This
should be clear when we consider the way natural
selection operates. Selection comes about only because individuals with genes helpful in overcoming
obstacles to reproduction pass those genes on,
whereas individuals with unhelpful or harmful
genes will tend not to pass them on since they will
have fewer or no offspring. Future environments
can’t sort individuals into those two categories—
those who successfully reproduce and those who
don’t. Only the present environment can. (p. 66)
Self-Test 2
1. d. (p. 61)
2. c. (p. 54)
3. a. (p. 55)
4. a. (p. 56)
5. a. Since your friend’s mother has blue eyes and
blue is recessive, you know her genotype; she has
two blue-eye alleles. Since your friend received
one of her genes for eye color from her mother,
she must have one blue-eye allele. Since she’s
brown-eyed, the other allele must be a dominant
brown-eye allele from her father. (p. 56)
6. d. The original purebred round-seed peas had
only round-seed alleles to contribute to offspring,
whereas purebred wrinkled-seed peas had only
wrinkled-seed alleles. In the F1 generation, all
peas have one round-seed allele and one wrinkled-seed allele. Because the F1 generation all had
round seeds, we know that round-seed alleles are
dominant. When F1 peas are bred with one another, one-fourth of the peas will have two wrinkled-seed alleles, one-fourth will have two
round-seed alleles, and the remaining peas will
have one of each type of allele. But because
round-seed alleles are dominant, all but the onefourth with two wrinkled-seed alleles will be
round-seeded. (p. 57)
7. b. (p. 52–53)
8. c. As the text states, mutation is ultimately the basis of all genetic variation, because it alone introduces truly new genetic information. (pp. 64–65)
9. d. The functionalist seeks to understand actual
behaviors, not potential behaviors, and the ways
they promoted survival and reproduction in the
species. (p. 67)
10. a. (pp. 68–69)
11. b. The case described is one resulting from convergent evolution. (p. 75)
12. d. (p. 67)
13. b. (p. 78)
14. d. (p. 86)
15. a. (p. 89)
16. Male primates are more aggressive than female primates as a general rule. Female aggression occurs,
but is more limited in scope, severity, and frequency.
Male aggression often has to do with sex. Male monkeys and apes may kill infants fathered by others to
stop their mothers from lactating so they will again
be available sexually. They may fight with other
males to improve their status and attractiveness and
may violently force females to submit to sex. The
pattern holds for humans, with men being much
more violent than women; sexual jealousy is a primary motive. Such male aggression increases the
chances of the male passing on his genes. There is
not such an advantage for females given their higher
parental investment. (p. 85)
17. Both kin-selection and reciprocity theories try to
reframe behavior that is apparently selfless as behavior that is in some sense selfish. Kin-selection
theory suggests that the gene promoting the “altruistic” act in an individual may be destroyed, but
other copies of the same gene in the individual’s
kin will be saved as a result; in this case, it is the
gene that is “selfish.” In reciprocity theory, there
is an expectation of the favor being returned at
some future time. This theory can help to explain
behavior that seems altruistic being directed toward non-kin. Female coalitions among bonobos
are an example from animal behavior. Humans are
the greatest practitioners of reciprocal helping,
though. They have effective ways to keep track of
help given, and emotions—such as a sense of fairness—that promote reciprocity. (p. 88)