Evolution of 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:

1. Reactive-expressive (e.g., verbal/physical).
2. Reactive-inexpressive (e.g., hostility).
3. Proactive-relational aggression (aggression that damages human relationships).

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.

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.

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 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.

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.