war and peace aggression in an evolutionary context
TRANSCRIPT
War and PeaceWar and Peace
Aggression in an Evolutionary Context
Aggression (1)Aggression (1)May be defined as “behavior that is
intended to injure another person who does not want to be injured” (Brehm et al., 1999)
May be Instrumental
Harm inflicted as a means to an end Emotional
Harm is inflicted for its own sake
Benefits Co-opting others’ resources Defense against attack Intrasexual competition Status hierarchies Deter rivals Deter sexual infidelity in mates
Aggression (2)Aggression (2)
Context-specificity Spousal violence due to jealousy Reputation and escalating retaliation Ability to retaliate
Size, strength, skillProximity of kin
Aggression (3)Aggression (3)
Instinct Theory: FreudInstinct Theory: FreudTwo specific instincts: Life (Eros) and
Death (Thanatos) Death instinct was a post WWI
concept, representing an unconscious desire to escape life through death
Aggression is caused by a conflict between Life and Death instincts, targeted towards others
In 1966, the ethologist Konrad Lorenz published On Aggression
Argued that aggression is adaptiveSuccessful aggression leads to securing
of Food Territory Mates
Instinct Theory: LorenzInstinct Theory: Lorenz
Tautological, untestable hypothesesDue to their inflexibility, they do not
effectively account for environmental influences that lead to cultural variation
Commit the nominal fallacy Assume an effect has been explained
simply by naming itThe problems with instinct theory,
however, do not refute the influence of evolution
Instinct Theories: ProblemsInstinct Theories: Problems
Sex Differences in Aggression Sex Differences in Aggression (1)(1)
Once again, we return to minimum investment Men have greater reproductive
variance, which is constrained by access to mates
Thus, men are in direct competition with each other for mates
The greater the variance (e.g., effective polygyny), the greater the sexual dimorphism
Overwhelmingly greater number of Murders perpetrated by males Male homicide victims
Females do, however, also engage in aggressive acts Verbal aggression is common Simple assault Serious harm is very rare, though
Sex Differences in Aggression Sex Differences in Aggression (2)(2)
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MalesFemales
Sex Differences in Aggression Sex Differences in Aggression (3)(3)
Campbell (1995)
Young Male SyndromeYoung Male SyndromeYoung men have the greatest degree of
intrasexual competition for matesThus, they employ riskier strategies
Hunting Combat Defense
Through reputation, these behaviours serve to impress females and deter rivals
Young Female Syndrome?Young Female Syndrome?Campbell argues that the overall
relationship between age and violence holds for females as well Teen girls and competition for mates
Biased sex ratio with fewer malesProportion of resource-rich males
Context Effects of Aggression Context Effects of Aggression (1)(1)
Male-Male Marital and employment status Status and reputation Sexual jealousy and intrasexual
rivalryFemale-Female
Intrasexual rivalry
Male-Female Sexual jealousy
Female-Male Defense against attack
Other effects Variation in testosterone (T) Heat effects Hypoglycemia (e.g., in Qolla)
Context Effects of Aggression Context Effects of Aggression (2)(2)
Circannual Rhythms of TCircannual Rhythms of T
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Fall Spring
Frequency of ViolentIncidents
2 (1) = 10.007, p = .002Krupp et al. (2002)
Heat EffectsHeat Effects
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Summer Fall Winter Spring
Frequency of ViolentIncidents
2 (3) = 34.44, p < .001Krupp et al. (2002)
Warfare (1)Warfare (1)Extremely sexually-dimorphic
behaviourBenefits
Increased sexual access Increased resources Improved reputations
Costs Death or injury Lowered reputation
Warfare (2)Warfare (2)Unique aspect of warfare is its cooperative
natureConditions for its evolution
Average long-term gain in reproductive resources must outweigh costs
Members must believe that success is likely
Risk and contribution of each member must be related to benefits
Veil of ignorance over likelihood of survival
Evolutionary Predictions (1)Evolutionary Predictions (1)Males will have adaptations for warfare
Historically, only males seek warSexual access will be primary benefit
For gangs and Yanomamö, this is trueAdaptations for defecting might also
have evolved when likelihood of death was high
Warfare should be more likely when chances of winning are high (e.g., number of soldiers) WWII and coalitional size
Adaptations to enforce “risk contract” Reputation
Males will have adaptations to prefer more able, willing men as coalitional members
Evolutionary Predictions (2)Evolutionary Predictions (2)
Group ProcessesGroup Processes It is extraordinarily easy to stimulate
intergroup competition (Us vs. Them)Robber’s Cave experiments
11 year old boys formed two groups Escalated competition rapidly over
one week Were only able to deescalate once
experimenters gave them a task that they could only perform together
The Wrap-UpThe Wrap-UpBenefits to aggressive behaviour Instinct TheoriesSex DifferencesYoung male & young female syndromesContext effectsEvolutionary perspectives on warfare
Things to ComeThings to ComeSexual conflict
Occurrence and timing of sex Jealousy Mate retention tactics Access to resources Rape