Evolutionary Explanation of aggression
Outline & Evaluate Hormonal Explanations of Aggression (20
marks)A01:Chemicals that regulate & control bodily
functionsTestosterone = Androgen (male hormone, released from
testes)10x higher in males than females (adrenal gland)15-25yrs =
peak testosterone age and age most likely to commit violent crimes
Animal studies can show effects of removal of testosterone sources
(neutering) Possible links between Low Levels of Cortisol +
aggression
A02Higher in athletes from aggressive sportsHigher in more
aggressive prison populations (Dabbs, 1995)Can increase aggression
in castrated mice (Wagner)Can increase anti-social competition in
men (Harrison)Possible link with low cortisolHOWEVER Data generated
from small, specific (prison) samplesGeneral population shows 0.14
correlation (other factors)Alternative explanation may be that
testosterone increases social dominancenot aggression
AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal
StudiesDeterminsm vs. Free WillEthnocentricism
3
Evolutionary Explanation of aggressionUnderstanding of
Evolutionary PsychologyEvolutionary theory Applied to AggressionKey
words: Parental Investment, Cuckoldry, Sexual Jealousy,
Adaptive
CuckoldrySexual JealousyAdaptiveParental InvestmentInclusive
Fitness
Inclusive FitnessMeasure of how successful individuals are in
passing on a high proportion of their genes to succeeding
generations
What is evolutionary Psychology?EP seeks to identify which human
psychological traits are evolved adaptations that is, the
functional products of natural selection or sexual selection in
human evolution
Evolutionary psychology
Evolutionary PsychologyAll behaviour is rooted in ensuring
reproductive success
Phobias, anorexia, gym, make up, dancing 10
Evolutionary PsychologySLT = we can learn to be
aggressiveDeindividuation = situations make us
aggressiveInstitutional = Institutions make you
aggressiveGenetic/Neural/Hormonal = Our biology make us predisposed
to aggressionEvolutionary = The Ultimate Reason for Aggression
Defend food / mates11
Evolutionary AggressionWhy was it adaptive to behave
aggressively?
How might aggressive behaviour in modern day be associated with
reproductive success?
Evolutionary PsychologyLorenz (1966)
Functions of Aggression1. Ensure only the fittest &
strongest mates selected for reproduction2. Ensure survival of
offspring3. Distribute a species in a balanced way in
territories
Parental InvestmentAny investment by the parent in an individual
offspring that increases the chance of offspring survival
Involves provision of resources, (food, energy, time,
territory)
Parental InvestmentThere is asymmetry in parental investment in
humans
Female egg cell is much more costly to produce than male sperm
cellFemales must nourish the offspring for 9 months, she is
therefore limited by number of offspringIn Western cultures,
females breast feed for between 3-12 months
Females must be choosier when it comes to potential male
mates
Females compete for quality of male matesMales compete for
quantity of female mates
69!2000!
Geghis 2000 gravata - 6916
Evolutionary PsychologySexual Jealousy based on suspected or
imminent sexual infidelity
Evolutionary psychologySexual Jealousy can be used as a
mitigating factor in court
In many cultures, a man has the right to beat or even kill his
unfaithful wife
In Western societies, murder charges can be reduced to
manslaughter if the male killed another male who was sexually
involved with the killers wife this is not the same for women.
cuckoldryInvesting in offspring that are not their own
Females can be certain if a child is their own, males cannot
Therefore males have a greater concern about the fidelity of
their mates than females
Cuckoldry risksRetaliation from male
Abandonment (loss of resources)Loss of invested resources
Loss of reproductive success
A01 evolutionary explanationCuckolded men risk losing resources
and reproductive opportunity. Males evolved aggressive
mate-guarding strategies to prevent being cuckolded. These are
driven by sexual jealousy, an adaptation evolved in males to deal
with parental uncertainty. Sexual jealousy prevents the female
mating with others so it is an adaptive response.
CuckoldrySexual jealousy may have evolved as a solution to these
problems
Buss (1992) Which is worse?A) The knowledge that your partner
has had sex with someone elseB) The knowledge that your partner has
developed a deep emotional bond with someone else
Buss (1992)85% of women chose option B deep emotional bond
60% of men chose option A
(The majority of the 40% of males who had chosen option A had
never been in a committed sexual relationship)
Which route to take1. Sow your wild oats with lots of women,
hoping that at least some of them mother your children
Or 2. Stick to 1 woman and watch her like a hawk so you can be
sure shes mothering only your children
Shackleford (2005) Claimed that men have evolved mate-retention
strategies to deter their mate from leaving/cheating.
He found that the more of these strategies seen in a
relationship, the more likely female-directed abuse will occur.
Shackleford (2005) 1. Vigilance
2. Emotional Manipulation
3. Monopolisation of Time
4. Possessive Ornamentation
Look in books for examples of each26
Shackleford (2005)72% of women who reported partners using
direct-guarding (not allowing them to talk to other men) required
medical attention after an assault by their partner
Aggression is an adaptive response to ensure reproductive
success
Daly & Wilson (1988)Peak reproductive age in males is early
20s
This age is also the most likely age to commit same-sex
homicide.
Daly & Wilson (1988)
Same-sex murder rates reflect evolved aggression due to sexual
jealousy
Daly & Wilson (1988)A lack of resources increases male-male
competition and risk of murder
Daly & Wilson (1988)Threat to male status
Females attracted to men with higher statusTherefore men seek
statusLoss of male status = loss of potential mates + possibly
resources.
What we know so farFactors affecting reproductive success can
increase aggressionA02(Buss Males sex>emotional bond)Shackleford
More mate-guarding = more violenceDaly & Wilson peak
reproductive males = peak violence - More male-male murders than
female - Less resources = more male-male murders
AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal
StudiesDeterminsm vs. Free WillEthnocentricism
33
Female AggressionStudies have found that females will use more
Verbal Aggression than males
How can this be explained by Evolutionary Psychology?
Size of females evolved34
Maladaptive Aggression?Ghiglieri (1999)Male lions & cheetahs
have been observed killing offspring (usually of rival males)
Reduces Inclusive Fitness (reproductive success) in rivalsMore
resources and less competition for own offspringCauses Rivals
lioness to go into oestrus (heat) sooner, allowing killer to
impregnate them with own offspring.
Other types of Aggression?
Other types of AggressionLorenz (1966)
Functions of Aggression1. Ensure only the fittest &
strongest mates selected for reproduction2. Ensure survival of
offspring3. Distribute a species in a balanced way in
territories
Lorenz - Xenophobia & Genocide Violence towards other
cultures is common
Lorenz believes this is due to Territorial Aggression driven by
evolved, primal survival tactics.
Xenophobia & GenocideWaller (2002)
Humans have evolved living in groups which need defined
boundaries creating in-groups and out-groupsAllows for resources to
be shared equally, reduces potential of free-ridersReduces
reproductive competition We have evolved xenophobic attitudes
towards out-group members to protect our ownGenocide is the
consequence of this xenophobia
However Individual Differences (not all men act aggressively
towards unfaithful partners)Suggests that violence is not a
universal response to sexual jealousy, thus not completely
evolutionary
Cultural Differences in Aggressive Behaviour
Cultural Differences in Aggressive Behaviour (Buss &
Shackleford, 1997)
Yanomami of South AmericaMale violence is required to attain
status
Kung San of NamibiaAggression leads to irreparable damage of the
aggressor
Describe & Evaluate the Evolutionary Explanation of
Aggression. (8 + 16 marks)A01
Lorenz 3 functions of aggressionAdaptive Increase reproductive
success & thus inclusive fitnessKey words Sexual Jealousy
CuckoldryMate-Retention StrategiesMale-male competitionTerritorial
Aggression
Try and write a paragraph now including all key words42
Describe & Evaluate the Evolutionary Explanation of
Aggression. (8 + 16 marks)A02:
Shackleford More mate-retention strategies = more
violence(supports notion of sexual jealousy driving aggression)Daly
& Wilson Age / Male-male homicide / Resources / Status(supports
idea of reproductive competition driving aggression)Female
Aggression = verbal (females less physical, verbal aggression
reduces status and deters males)Other types of Aggression
Xenophobia (Waller, 2002)(supports idea that aggression is created
by drive for in-group to survive)
43
AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal
StudiesDeterminsm vs. Free WillEthnocentricism
44