Chapter 74. Evolutionary Explanations

Learning Objectives

evolutionary psychology
study of the genetic changes produced by natural selection, and their influence on behavior and mental processes
mutation
random error in copying a gene during cell division
gene
segment of a DNA molecule that can synthesize a protein; located on chromosomes
natural selection
genetic variations that increase survival or reproduction will be passed to future generations
genome
the complete set of genetic instructions for each organism
reproductive success
attracting a mate and producing offspring that carry your genes
Evolutionary Explanations
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true
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Illustration: Show silhouettes evoking the famous drawings of evolution of species from monkeys to humans, but with a humorous twist, as for example, evolution leading humans back into a “hunched-over” posture when working on a computer or feeding a cat
Learning Objectives:

Describe the basic process of evolution guided by natural selection.

Identify evolutionary explanations for contemporary human behavior and preferences.

Review

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illustration: Show double helix of DNA molecule unwinding during replication, and producing an error in copying one gene; show double helix strands (blue in image) in light gray as thicker strands, with base pairs (vertical lines) in different colors; entire image could be shown in vertical orientation (similar to second reference image) rather than horizontal orientation; show replicated copies of gene as thick red strands (similar to model) with a single base difference between the correct copy and the mutation; off to the side, show “zoomed-in” views of the relevant gene, both in original form and the copies; highlight the corresponding target base locations on the two copies, showing the mutation in a different color; label “DNA molecule” at left side of double helix; label “Original gene” for designated sections of the two gray strands that are “zoomed-in” to show 5 base locations, not 4 as in model; flip the second gene-and-copy so that the original is on the outside for both genes and the copy is on the inside; label “Copied gene” for designated sections of red strands; show label “Mutation” with arrow pointing to the highlighted difference at the target base location

1. Genetic variation within a human population is produced by mutations, which are spontaneous random errors in copying genes when new cells are formed. Each gene synthesizes a particular protein. Because the mutated gene synthesizes a slightly different protein, a person carrying that gene will have different physical characteristics and different behavioral tendencies.

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The chart shows that mutation can lead to three outcomes. First, it can have no effect on survival. Second, it can increase the likelihood of survival. Third, it can decrease the likelihood of survival.

2. Most mutations don’t have much effect. Some mutations interfere with normal functioning, and thus make it less likely that individuals with that gene would survive. Occasionally, a mutated gene conveys a survival benefit, such as the mutation that allowed some early humans to digest milk from cows, thereby providing a new food source.

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Illustration: Clip-art type illustration of the nursery rhyme, “There was an old woman who lived in a shoe. She had so many children, she didn’t know what to do.”; no labels are needed for the illustration

3. Some genes don’t contribute to survival, but instead make an individual more attractive or less attractive to potential mates, or more likely or less likely to give birth to healthy offspring. Other genes produce behavioral tendencies to provide good care or poor care for one’s offspring. These genes influence reproductive success, which is the likelihood of passing one’s genes on to subsequent generations.

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Illustration: Flowchart shows outcomes of natural selection; in center, show blue text rectangle with label “Natural selection” and arrows pointing to the other two text rectangles; on left, show orange rectangle with label “Unfavorable traits become less common”, and blue downward-pointing arrow labeled “Evolutionary pressure”; on right, show green rectangle with label “Favorable traits become more common”, and blue upward-pointing arrow labeled “Evolutionary pressure”

4. The principle of natural selection predicts that genes (and the traits they enable) that carry a survival benefit or a reproductive benefit will become more frequent in a population, while genes that hurt survival or reproduction will become less frequent or even disappear from the human genome.

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Illustration: cartoon-type illustration of prehistoric life; EITHER a humorous treatment of sexist stereotypes in success at obtaining food and attracting a mate, OR an illustration of prehistoric life based on cave paintings from Neolithic period

5. Evolutionary psychologists argue that the physical and psychological characteristics that are common in humans today must have been honed by natural selection. We are all descendants of humans who possessed genes that favored survival and reproduction in a dangerous world with scarce resources.

Practice 1: Infant Taste Preferences

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Practice 1: Infant Taste Preferences

Use the checkboxes to indicate whether babies prefer or avoid each basic sensation. Then select the SUBMIT button.

Evolutionary psychology helps explain why some behaviors are common across many cultures. Let’s look at the example of taste preferences in young infants. Clearly, there are cultural differences in food preferences among adults, but most young infants around the world show similar reactions to the five basic tastes—sweet, sour, salty, bitter, and umami (savory). Which tastes do you think babies prefer?

Small baby tasting apple.
lina aidukaite/Getty Images
Babies prefer:
SWEET
SOUR
BITTER
SALTY
UMAMI
Babies avoid:
SWEET
SOUR
BITTER
SALTY
UMAMI

Practice 2: Explaining Gender Differences

practice_2
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Practice 2: Explaining Gender Differences

For each characteristic, indicate whether that characteristic is more important for males who are seeking a partner, or for females who are seeking a partner. Then, select the SUBMIT button.

Evolutionary psychology also helps explain some of the behavioral differences between adult males and females. Although each culture defines gender roles in its own unique way, across cultures the typical male is looking for specific qualities in a romantic partner, while the typical female is looking for a different set of qualities in a partner. Which package of traits is most appealing to each gender?

The table listing the traits has two columns and six rows. The first column contains a checkbox for females and males, where you designate which gender the trait is most important to in selecting a partner. The second column lists the characteristics of an ideal romantic partner. These include the following, from top to bottom: older and more mature; physically attractive; high status in community; slim waist and good overall health; ambitious with good financial prospects; and willing to commit to the relationship. Click on “Check Answer” when a checkbox has been selected for each row.
More important for: Characteristics of an ideal romantic partner:
females
males
 older, more mature
females
males
 physically attractive
females
males
 high status in community
females
males
 slim waist and good overall health
females
males
 ambitious, with good financial prospects
females
males
 willing to commit to the relationship

Quiz 1

matching_test

Quiz 1

Match the terms with their descriptions by dragging each colored circle to the appropriate gray circle. When all the circles have been placed, select the CHECK ANSWER button.

Perhaps you should go back to review the basic process of evolution guided by natural selection.
Select the NEXT button and move to Quiz 2.
genes
genome
mutations
reproductive success
natural selection
random errors in copying genes during cell division
attracting a mate and producing offspring that carry your genes
those genetic variations that increase survival or reproduction will be passed to future generations
the complete set of genetic instructions for each organism
segments of a DNA molecule that can synthesize a protein

Quiz 2

multi_mc_test

Quiz 2

For each statement, select one of the buttons to indicate whether the statement is True or False. When responses have been chosen for all of the statements, select the CHECK ANSWER button.

Select the NEXT button and move to the Conclusion.
Perhaps you should go back to review the basic process of evolution guided by natural selection.
True
False
Evolutionary psychologists claim that all genetic mutations confer benefits for survival and reproduction.
True
False
According to evolutionary psychologists, males today prefer young, attractive female partners because those males have been influenced by images in the media.
True
False
Evolutionary psychologists propose that infant taste preferences are universal because taste sensations are related to the nutritional value of the food.

Conclusion

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Illustration: Show silhouettes evoking the famous drawings of evolution of species from monkeys to humans, but with a humorous twist
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