Why does aggression exist? How is aggression useful for surviving as human beings? What is our evolutionary need in nature to act aggressively? Aggression manifests in different forms, and evolution dictates it serves a purpose. Let's explore the evolution of human aggression and look at the prevalence of intimate partner violence, male aggression, and bullying.
- We are going to explore the evolution of human aggression. First, we will give a definition of aggression in psychology.
- Then, we will briefly look at the causes of aggression in psychology.
- Next, we will examine two types of aggression in human evolution.
- After, we will briefly explore gender differences in aggression in psychology.
- Finally, we will evaluate evolutionary explanations of aggression.
Fig. 1 - There may be an evolutionary reason behind human aggression.
Definition of Aggression in Psychology
Aggression is acting on feelings of anger with violence or hostility. It is an innate trait that occurs in many different species, from dogs, cats, lions, hyenas, and humans. The evolutionary explanation accounts for how a species changes over millions of years, acquiring characteristics that enhance survival and reproduction through natural selection.
Psychologists are interested in exploring how and why humans feel and behave aggressively, and one way of exploring this is by looking at how humans have evolved.
There are three notable types of aggression in psychology:
- Reactive-expressive (e.g., verbal/physical).
- Reactive-inexpressive (e.g., hostility).
- Proactive-relational aggression (aggression that damages human relationships).
There are also several suggested causes for the innate reaction of aggression.
Causes of Aggression in Psychology
Aggression characterises itself as causing physical and psychological harm to yourself or others or things within the environment. It is destructive behaviour, but does it have any benefits? For evolutionary explanations, the answer has to be yes. Potential evolutionary causes of aggression could be:
- Defeating sexual rivals.
- Attaining and maintaining relationships with mates (deterring infidelity).
- Sexual jealousy of rivals.
- Dominance and social status.
- Gaining resources.
- Defending resources, the self, and family.
Fig. 2- Aggression may have been beneficial for human evolution.
Two Types of Aggression in Human Evolution
Sexual jealousy is suggested to be a main motivator in the escalation of aggressive behaviour in our evolution, mainly in male attempts at avoiding cuckoldry. Cuckoldry refers to raising a child that is not your own.
- Males fear cuckoldry because any investment in offspring that is not their own is a waste of resources, as the child will not have his genes.
The threat of cuckoldry can make men uncertain about child paternity and increase aggression. In the past, men were more successful if they avoided cuckoldry, so it is suggested psychological mechanisms have developed to increase anti-cuckoldry behaviours in males.
Example of Aggression in Psychology: Mate Retention Strategies
Retention strategies include direct guarding and negative inducements in psychology. They are mate retention strategies, specifically:
Direct guarding: male vigilance over a partner’s behaviour (e.g., checking who they’ve been seeing).
Negative inducements: the use of threatening awful things for unfaithfulness or leaving (e.g., ‘I’ll kill myself if you leave me').
Wilson and Daly (1996) identify mate retention strategies which are highly violent. These strategies result from the potential loss of female mates through infidelity or unintentional paternal investments when the child is not their own. Infidelity in wives is one of the major causes of violent rage in males, regardless of societal views of such behaviour towards women (some view it as reprehensible, whilst others view it as restoring a man’s honour).
Battered women in Wilson and Daly (1996) also stated jealousy was one of the primary reasons behind the motives of their husband's violent behaviour towards them.
Example of Aggression in Psychology: Intimate Partner Violence
Shackelford et al. (2005) studied heterosexual couples through different questionnaires. The men’s was about mate retention behaviours, and the women’s was called the spouse influence report, which measured the extent of their partner’s violence in their relationship.
Shackelford et al. (2005) found a strong positive correlation between male mate retention behaviours and women reporting physical violence. The researchers said that these retention behaviours reliably predicted husbands’ violence against their wives.
Gender Differences in Aggression: Psychology
Aggression and the source of the feelings differ in males and females. According to Griskevicius et al. (2009), for men, motives behind direct aggression, such as face-to-face confrontation, primarily revolved around status and were boosted by mating motives. Interestingly, mating motives were only boosted when other men were observing.
Women, however, had both status and mating motives, which only increased indirect aggression (social exclusion, etc.), and they became more directly aggressive when resources were scarce.
Testosterone is suggested to be a factor relating to aggression.
Typically, status and mating motives did not increase direct aggression in women.
Fig. 3 - There are gender differences in the evolution of aggression.
Buss et al. (1992) found sex differences in jealousy through a cross-cultural questionnaire study. They were given scenarios where their partners were suggested to be interested in other people. They were asked what would cause more distress: an emotional or sexual relationship with the other person.
More men than women found sexual infidelity more distressing than emotional infidelity. It was suggested that jealousy in men results from paternal uncertainty, and jealousy in women is apparent more due to the emotional threat of a man leaving them for another woman.
It was suggested this feeling is innate, not learned (as it was generalisable across cultures), but as it was hypothetical, it is not entirely valid.
Bullying occurs because of a power imbalance. A more powerful person uses deliberate, repeated aggression against a weaker person. People often think bullying results from maladaptive behaviours, e.g., childhood abuse., but our evolutionary ancestors may have used bullying to increase their survival by increasing their chances of reproduction.
Volk et al. (2012) argue that bullying characteristics are attractive to the opposite sex. In males, this refers to dominance and strength. These characteristics can also help males fend off rivals.
They, therefore, have the perfect combination of attracting females and warding off rivals, leading to greater reproductive opportunities. In females, bullying often occurs within a relationship and is about control. Women bully to keep their partner’s fidelity, meaning he will provide her and their offspring with resources.
Evolutionary Explanation of Aggression Evaluation
We need to assess the explanations and identify their reliability and validity. Let's explore the strengths and weaknesses of the evolutionary explanation of aggression.
Strengths
Many studies, including that of Shackelford et al. (2005) mentioned earlier, show that mate retention strategies are linked to sexual jealousy and aggression. Shackelford’s study shows that the greater the perceived risk of infidelity/cuckoldry, the greater the aggression. This finding supports the idea that we can evolutionarily explain aggression.
Evolutionary theory explains gender differences, e.g., men engaging in aggressive acts more than women. Females are less likely to be physically aggressive, as this could hurt them or their offspring (Anne Campbell 1999), but more likely to be verbally aggressive to keep their partner who provides resources for them.
This ability to explain gender differences is a strength of the evolutionary theory.
Evolutionary explanations show us that bullies bully because they can gain advantages. Volk et al. (2012) argue that we need to increase the cost of bullying and increase the rewards of alternatives.
Weaknesses
Cultural differences can play a significant role in aggression.
For example, the Kung San people of the Kalahari have very negative attitudes towards aggression and discourage it from childhood.
In contrast, the Yanomamo of Venezuela and Brazil are called the ‘fierce people’ because they value and reward aggression.
It is also tough to test hypotheses about evolutionary behaviours to solve adaptation problems in our past. Most of our research is correlational, allowing us to draw cause-and-effect conclusions.
Evolution of Human Aggression - Key takeaways
- Evolutionary explanations account for how a species changes over millions of years, acquiring characteristics that enhance survival and reproduction through natural selection.
- Potential evolutionary reasons behind aggression can include defeating sexual rivals, attaining and maintaining relationships with mates (deterring infidelity), sexual jealousy of rivals, dominance and social status, gaining resources and defending resources, the self, and mates.
Men experience paternity uncertainty because they can never be sure if they have fathered a child.
Wilson and Daly (1985) found in a study on murders occurring in the Detroit area that the vast majority of killers and those killed were male (young men, specifically), and a chunk of these cases resulted from escalated disputes concerning status.
Retention strategies include direct guarding (male vigilance over a partner’s behaviour) and negative inducements (the use of threatening awful things for unfaithfulness or leaving).
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