CHAPTER 3: COMBATING THE HOSTILE FORCES OF NATURE:
HUMAN SURVIVAL PROBLEMS
Chapter Summary
Food shortages, toxins, predators, parasites, diseases, and extremes of climate are hostile forces of nature
that recurrently plagued our ancestors. Humans have evolved adaptions to combat these impediments to
survival. One of the most important survival problems is obtaining food. In addition to food shortages,
organisms face the problem of selecting which foods to consume (e.g., those that are rich in calories and
nutrients),selecting which foods to avoid (e.g., those that are filled with toxins), and actually procuring
edible foods. Humans evolved as omnivores, consuming a wide variety of plants and animals. Among the
human adaptations are specific food preferences for calorically rich food; specific mechanisms for
avoiding the consumption of toxic food, such as the emotion of disgust in response to pathogen-carrying
food items such as rotting meat or spoiled fruit; and mechanisms for getting rid of toxins such as gagging,
spitting, vomiting, coughing, sneezing, diarrhea, and pregnancy sickness. People also use spices that kill
off food-borne bacteria, a practice that likely spreads through cultural transmission, supporting the
antimicrobial hypothesis. Our taste for alcohol probably originated in the eating of ripe fruit, since ripe
fruit contains low levels of ethanol. The use of fire to cook foods may have been critical in human
evolution, functioning both to kill dangerous disease-producing microbes and to render a wider array of
potential foods more easily digestible.
All habitats contain hostile forces that impede survival. Humans have evolved a variety of specific fears
to avoid these dangers. The human fears of snakes, spiders, heights, and strangers, for example, appear to
be present across a variety of cultures and emerge at specific times in development, suggesting adaptive
patterning. Humans have at least six behavioral responses to a fear-inducing stress: Freeze, flight, fight,
submit, fright, and faint. In addition to fears, humans appear to have predictable biases in their attention:
They can easily pick out snakes and spiders amid an array of non-dangerous images. Humans have an
auditory looming bias that gives us an extra margin of safety when we hear sounds of danger
approaching. We also have the descent illusion, overestimating heights when viewed from the top
compared to when viewed from the bottom—an adaptation likely designed to prevent dangerous falls
from heights. Finally, children as young as age three appear to have a sophisticated understanding of
death as a result of an interaction with a predator.
Given the importance of survival in the evolutionary scheme of things, why people die (or do not live
longer) poses an interesting puzzle. The theory of senescence explains why. Basically, selection is most
potent early in life because any events that happen early can affect the entire span of a person’s
reproductive years. As people get older, however, the power of selection weakens; in the extreme, a bad
event that happened to you right before you died would have no effect on your reproduction. This means
that selection will favor adaptations that give beneficial effects early in life, even if they come with heavy
costs later on.
Perhaps even more puzzling is the phenomenon of suicide—when a person intentionally ends his or her
own life. Suicidal ideation occurs most commonly among those with poor reproductive prospects, who
experience failure at heterosexual mating, who are in poor health, who have poor financial prospects for
the future, and who perceive themselves to be a large burden on their kin. Evidence points to the
possibility that
humans have evolved context-sensitive psychological mechanisms to evaluate future reproductive
potential and net cost to genetic kin.
Suggested Readings
Campbell, A. (2013). A mind of her own: The evolutionary psychology of women. Oxford: Oxford
University Press.
Gelman, S. A. (2003). The essential child: Origins of essentialism in everyday thought. New York:
Oxford University Press.
Hill, K., Hurtado, K., & Walker, R. S. (2007). High adult mortality among Hiwi hunter-gatherers:
Implications for human evolution. Journal of Human Evolution, 52, 443–454.
Jackson, R. E., & Cormack, J. K. (2007). Evolved navigation theory and the descent illusion. Perception
and Psychophysics, 69, 353–362.
Krasnow, M. M., Truxaw, D., Gaulin, S. J. C., New, J., Ozono, H., Uono, S., Ueno, T., &
Minemoto, K. (2011). Cognitive adaptations for gathering-related navigation in humans.
Evolution and Human Behavior, 32, 1–12.
Multiple Choice Questions
(a) parasites
(b) predators
(c) kin
(d) bad weather
(a) the intuition that living things come in discrete packets that correspond to distinct species
(b) the application of popular biological concepts to everyday living
(c) the intuition that multiple biological concepts can be integrated into one unifying concept
(d) cognitive adaptations that are interpretable from various theoretical frameworks
(a) three
(b) five
(c) ten
(d) fourteen
(a) a byproduct
(b) an adaptation
(c) a highly variable phenomenon across cultures
(d) a tendency to disbelieve in biological properties as having evolved
(a) byproduct of other nutrients being absorbed into the plant
(b) method of storing nutrients that they may need
(c) adaptation for reducing the likelihood of getting eaten
(d) adaptation for chemical warfare against other plants
(a) a strategy of courtship
(b) a sign of closeness in relationships
(c) a method of unburdening oneself from food preparation
(d) a means of reducing conflict with rivals
(a) signaling to others dislike of something
(b) expelling toxins
(c) providing an emotional cue to damaging toxins
(d) protecting the body against ingesting or coming into contact with toxins
8. Which of the following was presented as evidence that humans may have evolved the ability to
(a) Women were willing to eat chocolate when formed in the shape of dog feces.
(b) Mothers rated the smell of their own infants’ feces as less disgusting than the feces of other
infants, even when mislabeled.
(c) Children tend to put novel items into their mouths, even those items which are considered
disgusting by adults.
(d) Humans have never resorted to cannibalism, no matter how dire the circumstances.
(a) individuals will spice foods more in colder climates
(b) individuals will spice foods more in hotter climates
(c) individuals will be more averse to microbes in hotter climates
(d) individuals will be more averse to microbes in colder climates
(a) higher
(b) lower
(c) equal
(d) not present
(a) drinking alcohol is an adaptation designed to reduce parasite loads
(b) drinking alcohol is a byproduct of adaptive preferences for decreased inhibition
(c) drinking alcohol is an adaptation designed to increase the likelihood of gaining access to
attractive mates
(d) drinking alcohol is a byproduct of adaptive preferences for ripe fruits
(a) avoiding toxins that could harm the mother
(b) avoiding toxins that could harm the developing baby
(c) decreasing demands on fathers to test their willingness to invest in offspring
(d) increasing the likelihood that a mother will spontaneously abort an unwanted fetus
13. Women who do not have pregnancy sickness during the first trimester of their pregnancy are
(a) three times more
(b) three times less
(c) thirty times more
(d) thirty times less
14. The embryo protection hypothesis predicts that women who failed to protect embryos in ancestral
(a) failed to survive long enough to reproduce
(b) failed to become our ancestors
(c) had a more difficult time attracting mates than women who could protect embryos
(d) invested more in other relatives’ offspring
(a) hunting
(b) gathering
(c) provisioning
(d) scavenging
(a) gathering
(b) provisioning
(c) scavenging
(d) none of the above
(a) human fossil evidence
(b) animal fossil evidence
(c) the modern psychology of some animals to avoid humans
(d) modern vitamin deficiencies
(a) humans have been designed by natural selection to provision their offspring
(b) males are unique among primates in their relative parental investment in children
(c) males supply food to competitors to gain social status among members of their group
(d) females maintain closer proximity to males who share meat because they benefit from their
hunting skills
19. Hunting can account for the emergence of all but which of the following patterns of human behavior?
(b) sexual division of labor
(c) male coalitions
(d) social exchange
(a) one argues that men provided for their families and the other that men provided food to non-
family members to gain social benefits through increased status
(b) one argues that men should spend less time hunting and the other, more
(c) one argues that the majority of caloric intake is through meat and the other through vegetables
(d) one argues that women should be impressed by a male’s hunting prowess and the other that
women should not be impressed by a male’s hunting prowess
21. The gathering hypothesis suggests a greater role for__________ in the evolution of human behavior.
(b) men
(c) social exchange
(d) women
(a) How much food her female kin have collected
(b) The amount of food her husband brings back from a hunt
(c) How well she scores on spatial tasks including location memory
(d) Her interest and enjoyment of foraging for food
23. Which of the following could be presented as evidence for evolved psychological mechanisms
(a) Children, when presented with both meat and plant products, tend to eat more plant products.
(b) Women prefer the taste of plant products more than men.
(c) Women locate specific plants within a large complex array more quickly and accurately than
men.
(d) Women take longer to memorize the scientific names of plants than men, but tend to
remember them for an extended period of time.
24. The !Kung practice of “the owner of the arrow is the owner of the meat” is the type of custom
(a) handicap
(b) gathering
(c) showoff
(d) provisioning
25. Scavenging ____________ hunting as a major source of food acquisition in ancestral environments.
(b) did not rival
(c) replaced
(d) was replaced by
(a) preferences to settle in environments with abundant resources
(b) preferences to settle on islands
(c) humans who did not prefer to settle in resource-rich environments
(d) better spatial skills in resource-rich environments
(a) location
(b) selection
(c) information gathering
(d) exploitation
(a) freezing or becoming immobile
(b) aggressive defense
(c) submission or appeasement
(d) social contact
(a) signaling to an attacker that one is not a threat
(b) becoming alert, watchful, and vigilant
(c) remaining still to trick predators sensitive to motion cues
(d) raising blood pressure and heart rate for a surprise escape attempt
(a) freeze
(b) appease
(c) fright
(d) faint
(a) maintaining proximity to a caregiver
(b) benefiting through the experience of a caregiver
(c) increasing food consumption
(d) avoiding ingestion of teratogens
32. Women show ________ fear of events that could lead to injury compared to men because
(a) less; women would have encountered such events less frequently throughout our evolutionary
past
(b) less; women have evolved more defenses against such attacks
(c) greater; women have evolved a more cautious strategy whereas men have evolved to take
greater risks
(d) greater; women would have encountered such events more frequently throughout our
evolutionary past
(a) the human tendency to take few risks
(b) the human tendency to overgeneralize dangers to unlikely triggers
(c) the human tendency to overstate one’s social importance
(d) the human tendency to overstate the political objectives of allies and foes
(a) deter closely related individuals from coming near you
(b) increase aid from one’s kin
(c) reduce the amount of iron in one’s blood
(d) reduce the effects of various diseases
(a) the deterioration of all bodily mechanisms as an organism ages
(b) humans’ fears related to adaptive problems in ancestral environments
(c) an elevated amount of iron in one’s blood
(d) the process whereby a gene can have two or more effects
(a) have beneficial effects
(b) have no effects
(c) have detrimental effects
(d) be higher
(a) most reproduction has already occurred
(b) little empirical work has examined the effects selection had on older adults
(c) selection operates more strongly on women than on men
(d) there are fewer men alive later in life
(a) women have greater variability in reproduction
(b) men have greater variability in reproduction
(c) men are larger than women
(d) men die sooner than women
39. De Catanzaro found that the frequency of sex is ____________ correlated with suicidal ideation in
(a) positively
(b) not
(c) negatively
(d) falsely
(a) an individual is away from home
(b) an individual is middle-aged
(c) an individual has too many burdens posed by dependent children
(d) an individual perceives an inability to contribute to his or her own inclusive fitness
(a) Men; experience an unexpected status gain
(b) Men; are of old age
(c) Women; are of old age
(d) Women; are menstruating
(a) Stone tools have been consistently found in the same sites as bones from large game animals.
(b) Divorcing men for a failure to provide food is not uncommon in tribal groups.
(c) Humans’ diets generally consist of 20–40 percent meat.
(d) Men generally engage in most or all of the hunting while women do most of the gathering.
(a) by getting all their calories from their mother’s milk
(b) by growing a temporary set of “baby” teeth that are replaced with permanent teeth later in life
(c) by delaying the development of specialized taste receptors
(d) by exhibiting taste neophilia: the preference for novel tastes
(a) salty
(b) bitter
(c) sour
(d) sweet
45. The fact that children everywhere need to be coaxed into eating certain foods, such as broccoli and
(a) the potlatch effect
(b) the provisioning hypothesis
(c) taste neophobia
(d) taste neophilia
(a) because men possess other adaptations that help them avoid disease: namely, lower sensation
seeking
(b) because their immune systems are less robust than men’s
(c) because they have to take care of infants and children who have less developed immune systems
(d) all of the above
47. Which of the following pieces of evidence illustrates that disgust is still adaptive in the current
(a) People who are most easily disgusted have fewer infections.
(b) Babies show evidence of disgust from birth.
(c) Women are more easily disgusted than men by disease-carrying objects.
(d) People find more materials in the modern environment to be disgusting than materials found in
ancestral environments.
48. When a rat eats a familiar food and a novel food at the same time and illness is induced, it
(a) avoids the familiar food
(b) avoids the novel food
(c) avoids all food for about twenty-four hours
(d) increases foraging behavior
49. Which of the following represents the relative degree to which pregnant women experience food
(a) coffee, meat, bread
(b) bread, vegetables, meat
(c) vegetables, coffee, bread
(d) coffee, bread, eggs
(a) The foods that pregnant women find most disgusting are the ones most likely to contain toxins.
(b) Pregnancy sickness peaks two to four weeks after conception.
(c) Women who do not experience pregnancy sickness are more likely to experience a spontaneous
abortion.
(d) all of the above
(a) Cooking is universal among human societies.
(b) Humans experience lower fitness on raw food diets.
(c) Cooking decreases the net energy value of the food.
(d) Digesting raw foods burns more calories because they are harder to digest.
(a) vertical distances seem larger when at the bottom of a mountain than at the top of a cliff
(b) vertical distances seem larger when at the top of a cliff than at the bottom of a mountain
(c) horizontal distances seem smaller to men who have evolved to travel long distances during
hunting
(d) horizontal distances seem smaller to women because they are shorter and thus closer to the ground