CHAPTER 10: AGGRESSION AND WARFARE
Chapter Summary
From the perspective of evolutionary psychology, aggression is not a singular or a unitary phenomenon.
Rather, it represents a collection of strategies that are manifested under highly specific contextual
conditions. The mechanisms underlying aggression have emerged, in this view, as solutions, albeit
sometimes repugnant ones, to distinct adaptive problems such as resource procurement, intrasexual
competition, hierarchy negotiation, and mate retention.
From this perspective, we expect variability in aggression—between the sexes, among individuals, over
the life span, and across cultures. It illustrates the point that variability does not imply that biology is
irrelevant. An evolutionary psychological perspective is truly interactionist: It specifies a set of causal
conditions in which particular features of the perpetrator, victim, social context, and adaptive problem are
likely to evoke aggression as a strategic solution.
An evolutionary perspective suggests at least six classes of benefits that would have accrued to ancestors
who used an aggressive strategy: co-opting the resources of others, defending oneself and one’s kin
against attack, inflicting costs on intrasexual rivals, negotiating status and power hierarchies, deterring
rivals from future aggression, and deterring long-term mates from infidelity or defection.
Many contexts are linked with aggression occurring within each sex-of-perpetrator by sex-of-victim
combination. Contexts triggering men’s aggression against other men include being unemployed and
unmarried—circumstances that suggest that men are on a path to being excluded from mating, which may
trigger a risky aggressive strategy. Men also aggress against other men when their status and reputation
are threatened and when they observe or suspect a rival of sexually “poaching” on their mate.
Women aggress against other women primarily in the context of competition over attracting or retaining
mates, over friendship violations, and sometimes over food. Women, however, are far less likely to use
physical aggression, preferring instead to derogate their competitors verbally or to socially ostracize them.
Two prominent derogation tactics are calling their rivals promiscuous and impugning their rival’s
physical appearance—both of which attain their effectiveness because they violate men’s desires in a
long-term mate.
Warfare, defined as aggression by a cooperative coalition against another cooperative coalition, is
extraordinarily rare in the animal world. Only two mammalian species have been observed to engage in
coalitional aggression: chimpanzees and humans. An evolutionary perspective predicts that warfare will
be practiced primarily by men, with the primary reproductive benefit being increased sexual access to
women. Empirical evidence supports this theory: Men have engaged in warfare throughout human
recorded history; sexual access to women appears to be a recurrent benefit that flows to victors of
warfare; men more than women spontaneously assess their fighting ability relative to others; and men
more than women value coalition members who are strong, are brave in the face of danger, and have good
Suggested Readings
Buss, D. M. (2005). The murderer next door: Why the mind is designed to kill. New York: Penguin.
Campbell, A. (1999). Staying alive: Evolution, culture, and women’s intrasexual aggression. Behavioral
and Brain Sciences, 22, 203–252.
Chagnon, N. (1988). Life histories, blood revenge, and warfare in a tribal population. Science, 239, 985–
992.
Daly, M., & Wilson, M. (1994). Evolutionary psychology of male violence. In J. Archer (Ed.), Male
violence (pp. 253–288). London: Routledge.
Duntley, J. D., & Shackelford, T. K. (Eds.). (2008). Evolutionary forensic psychology. 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.
Johnson, D. D. P., McDermott, R., Barrett, E. S., Crowden, J.,Wrangham, R., Mcintyre, M. H., & Rosen,
S. P. (2006). Overconfidence in war games: Experimental evidence on expectations, aggression,
Multiple Choice Questions
1. The discovery of chimpanzees raiding a neighboring territory to assault an enemy led researchers to
(a) the long-held assumption that other primates are peaceful and that only humans kill their own
(b) the long-held assumption that other primates only kill others individually rather than in
cooperative alliances
(c) the motives that led the chimpanzees to commit this act
(d) whether the chimpanzees were consciously aware of their goal
2. Buss and Shackelford proposed all of the following EXCEPT __________ as adaptive problems that
(a) co-opting the resources of others
(b) defending against attack
(c) inflicting costs on intersexual rivals
(d) negotiating status and power hierarchies
(a) co-opt land possessed by others
(b) acquire reproductively relevant resources
(c) both (a) and (b)
(d) neither (a) nor (b)
(a) manipulate the resources of intersexual rivals
(b) prevent the loss of status and honor that might otherwise results from being victimized
(c) both (a) and (b)
(d) neither (a) nor (b)
(a) boost one’s self-esteem
(b) signal one’s physical prowess to a mate
(c) increase status across contexts
(d) inflict costs on same-sex rivals
(a) prevent potential harm to one’s mate and children
(b) gain a reputation of submissiveness
(c) decrease the reproductive success of the attacker
(d) none of the above
(a) male sexual jealousy
(b) men “saving face”
(c) alcohol consumption
(d) loss of status
(a) men who are higher in relative mate value than their wives
(b) men who are lower in relative mate value than their wives
(c) women who are higher in relative mate value than their husbands
(d) women who are lower in relative mate value than their husbands
(a) caloric cost
(b) retaliatory aggression
(c) vulnerability of undefended kin
(d) potential of cuckoldry while a perpetrator of aggression is away from his wife
10. Nisbett pointed out that failure to aggress when aggressed against in “cultures of honor” can result in
(a) loss of status
(b) increase in status
(c) banishment by other group members
(d) greater rates of sexual abuse
(a) lower densities of kin; aggression towards their children
(b) higher mate value; aggression towards their children
(c) higher densities of kin; domestic violence
(d) low mate value; domestic violence
(a) access to reproductive age women is greater
(b) one lives in a culture that condones violence
(c) contexts that trigger aggression are encountered
(d) the individual has learned to associate aggression with acquired resources
13. Of homicides committed in Chicago between 1965 and 1980, _____ percent were committed by men.
(b) 50
(c) 69
(d) 86
14. In _______ cultures studied to date, men are overwhelmingly more often the perpetrators of homicide
(a) all
(b) most
(c) only a few
(d) no
(a) high-status men
(b) reproductive-aged women
(c) post-reproductive-aged women
(d) other men
16. Which theory provides the starting point for understanding why most murderers AND murder victims
(a) parental investment theory
(b) parent-offspring conflict theory
(c) multilevel selection theory
(d) reciprocal altruism theory
17. Homicide data reveal that men who are _________ and ___________ are most likely to commit
(a) poor; married
(b) rich; unmarried
(c) poor; unmarried
(d) rich; married
18. Within primate species, the ___________ effective polygyny, the ___________ sexual dimorphism.
(b) greater the; greater the
(c) less the; greater the
(d) none of the above
(a) high-status women
(b) reproductive-aged men
(c) post-reproductive-aged men
(d) other women
(a) less florid
(b) premeditated
(c) less violent
(d) less risky
21. Campbell argues that selection may operate against women who take great physical risks such as
(a) they bear the brunt of parental care
(b) the selective history of intersexual competition has not existed for women
(c) the selective history of intrasexual competition has not existed for women
(d) selection pressures for reciprocal altruism operate more strongly on men than on women
(a) aggressive fantasies
(b) verbal aggression
(c) physical aggression
(d) imitative aggression
23. Male victims of bullies were more often _____________ while female victims were more often
(a) stolen from; physically hurt
(b) the object of nasty rumors; called nasty names
(c) physically hurt; the object of nasty rumors
(d) called nasty names; stolen from
(a) preschool
(b) elementary school
(c) middle school
(d) high school
25. Women tend to engage in mostly ____________, while men tend to engage in mostly ___________.
(b) opposite-sex aggression; same-sex aggression
(c) indirect aggression; direct aggression
(d) direct aggression; indirect aggression
26. Burbank’s study of an Australian aboriginal tribe revealed that, of all the aggressive episodes
(a) 3
(b) 25
(c) 75
(d) 97
(a) the phenomenon of younger men being the most prone to form cooperative alliances for the
purpose of exacting revenge
(b) the phenomenon of younger men being the most prone to engaging in risky forms of
aggression
(c) the tendency of younger males to abuse their partners at higher rates than older males
(d) the decreased ability of younger males to withdraw from conflicts
28. Men in their _________ are most likely to be the victim of a homicide; they are ____ times more
(a) teens; two
(b) teens; six
(c) mid-twenties; two
(d) mid-twenties; six
29. Males of many species have to impress the females with their physical prowess in order to gain sexual
(a) IQ
(b) reputation
(c) earlier menstruation
(d) intrasexual competition
(a) slightly negative
(b) slightly positive
(c) strongly negative
(d) strongly positive
(a) 24 percent
(b) 61 percent
(c) 92 percent
(d) 100 percent
(a) physical appearance
(b) intelligence
(c) social status
(d) height
33. The most common complaint of husbands about their inability to control their wives was __________.
(b) her drinking
(c) his drinking
(d) her relationship with her family
34. ____________wives and girlfriends are more likely to be killed by their intimate partner than
(a) Nonaggressive; aggressive wives and girlfriends
(b) Older; younger husbands and boyfriends
(c) Older; younger wives and girlfriends
(d) Younger; older wives and girlfriends
35. Autonomy-limiting behaviors are __________ correlated with violence perpetrated by husbands
(a) negatively
(b) positively
(c) not
(d) moderately
36. Compared to women, the rates at which men slap, spit on, and hit their intimate partners are
(a) higher
(b) lower
(c) roughly the same
(d) not assessable
37. Which of the following is NOT an essential condition that must be met for adaptations to evolve for
(a) The average long-term gain in reproductive resources must be sufficiently large to outweigh
the reproductive costs of engaging in warfare over evolutionary time.
(b) Members of coalitions must believe that their group will emerge victorious.
(c) The risk that each member takes and the importance of each member’s contribution to the
success must translate into an inequitable share of the benefits.
(d) Men who go into battle must be cloaked in a “veil of ignorance” about who will live or die.
(a) Assess their fighting ability more frequently than do women
(b) Are more likely to go to war
(c) Have psychological mechanisms to enforce the risk contact
(d) Have been selected to be exposed to some risk of death at rates higher than women
39. ____________ report a greater number of sexual partners over a thirty-day period than do
(a) Yanomamö; !Kung
(b) Non-unokais; unokais
(c) Male gang members; non-gang-member peers
(d) Women; men
40. How many cultures have been identified so far in which women form coalitions designed to kill other
(a) zero
(b) three
(c) eleven
(d) thirty-one
(a) derogation
(b) land
(c) money
(d) women
42. Within the Yanomamö, men are distinguished as either unokais (those who have killed) or non-
unokais (those who have not killed). In their early twenties, unokais already had ___ times more ______
(a) four; surplus meat
(b) two; surplus meat
(c) four; wives
(d) two; wives
43. Duntley conducted a survey in which men and women were asked to rate how likely they would be to
kill an intrasexual rival in various situations if the crime would never be discovered. Which of the
following represents the condition in which women indicated a higher likelihood of killing the rival than
(a) The rival had sex with your mate.
(b) The rival was attractive.
(c) The rival beat you up.
(d) The rival humiliated you.
44. The theory that humans—especially men—have evolved specific psychological mechanisms that
(a) homicide adaptation theory
(b) slip-up hypothesis
(c) autonomous aggression hypothesis
(d) Kenrick-Sheets hypothesis
(a) does not apply to mating contexts
(b) explains situations in which anger occurs in the absence of precipitating factors
(c) proposes that anger functions to increase a target’s valuation of one’s welfare
(d) all of the above
46. Which of the following individuals should be MOST anger-prone, according to the recalibration
(a) an elderly woman
(b) a low-status man
(c) a short, weak man
(d) a young, beautiful woman
47. Which of the following traits was associated with more anger-proneness among men but not women?
(a) strength
(b) age
(c) attractiveness
(d) intelligence
(a) Individuals with more nearby kin are more anger-prone than individuals lacking nearby kin.
(b) Individuals viewing angry faces are more likely to behave altruistically in subsequent economic
games.
(c) High-status men and women are more anger-prone than low-status men and women.
(d) all of the above
49. After being primed with ________ cues, ________ report higher desires to react with direct
(a) status; women
(b) status; men
(c) kinship; men
(d) kinship; women
50. Men who were bullied when in school end up having fewer sex partners than men who were not
(a) Status loss still results in fitness-relevant consequences among men.
(b) Physically aggressive men are preferred by women as mates.
(c) Submissive men are preferred by women as mates.
(d) none of the above
(a) a man’s lower-body strength from facial photographs
(b) a man’s upper-body strength from facial photographs
(c) a woman’s lower-body strength from facial photographs
(d) a woman’s upper-body strength from facial photographs
52. In traditional cultures, men’s mortality rate due to warfare and homicide is quite high, sometimes even
(a) there was likely recurrently high selective pressure on men to evolve anti-homicide mechanisms
(b) men with aggressive tendencies would rarely reproduce
(c) children exposed to this contingency between men’s aggression and early death would exhibit less
aggression in adulthood
(d) the heritability of aggressive traits is low
53. Men’s tendency to derogate out-group members as sub-human or animalistic likely functions to
(a) decrease the probability of inter-breeding with out-group women
(b) help convince in-group women to support warfare efforts
(c) devalue out-group goods during intergroup social exchange
(d) lower inhibitions to kill out-group members