Discuss evolutionary explanations of human aggression. (9 marks + 16 marks)

You should outline and evaluate evolutionary explanations of elements of aggression such as infidelity and jealousy.


Aggression in men has an adaptive value. Men are more likely to experience sexual jealousy because of their fear of cuckoldry. Because men are more prone to parental uncertainty, they risk unwittingly investing resources in children who aren't their own. Sexual jealousy and the aggression which it can cause, therefore, evolved to deter females from sexual infidelity and hence minimise the risk of cuckoldry.

To do this, men have evolved retention strategies to deter mates from infidelity. This includes direct guarding, in which a male is especially vigilant to their mate in order to restrict her sexual autonomy. Retention strategies can also include violence against the woman. In extreme cases, an unintended consequence of this evolutionary behaviour may be her death (uxoricide).

Research has supported the relationship between male retention strategies and violence. Shackleford et al. found that men's use of retention strategies was positively correlated with violence scores. Women's responses also confirmed this, with evolutionary male retention strategies leading to violent behaviour towards them.

The explanation of uxoricide as being a consequence of sexual jealousy cannot account for the fact that younger women are at much greater risk of uxoricide regardless of their partner's age. The finding that men kill their wives when they're most reproductively valuable contradicts evolutionary logic. However, the evolved homicide module theory explains this by pointing out that a partner's infidelity carries a double loss for a male. He loses a partner (which damages his reproductive fitness) and another male gains his partner, increasing his own fitness.

A problem for these evolutionary explanations of aggression is that most studies of infidelity have focus solely on men's retention strategies and violence against women. It has been argued that women practise retention strategies and carry out assaults on their partner as often as men do. This would suggest that our current understanding of mate retention strategies is limited due to this gender bias.

Another problem with this perspective is that the social environment is constantly changing, so having flexible and behaviour that is responsive to these changes would be more adaptive than having a fixed set of behaviours. Because of this, using retention strategies and violence may not be adaptive in some cases.

This understanding has a real-world application. The use of mate retention strategies can be seen as an early indicator of potential partner violence. It therefore has value in alerting others to intervene before actual violence against the partner can occur.

    Aggression resulting in homicide can also be explained in evolutionary terms. One factor that may lead to homicide is increased male-male competition, a response which occurs when there's a lack of resources or difficulty attracting long-term mates. Wilson & Daly analysed homicides in Detroit and found that 43% of male perpetrators were unemployed (lack of resources) & 73% were unmarried (lack of relationship).

    Homicide can also be due to sexual jealousy. Daly & Wilson found that 92% of murders occurring in 'love triangles' were male-male, suggesting that male sexual jealousy is a key motivator of same-sex aggression and homicide.

    A consequence of man's evolutionary tendency to commit homicide in certain situations is that humans have evolved anti-homicide defences. Because of this, homicide is often a very costly strategy. As a response, selection favours the development of deceptive strategies such as concealment of homicidal intent from victims to avoid activating their homicidal defences.

    There are limitations to this evolutionary explanation, such as the fact that there are individual differences. This approach cannot explain why some men react differently to the same stimulus. This suggests that violence is not a universal response to sexual jealousy, and thus that it is not completely evolutionary.

    This perspective is also unable to explain why, if this is a universal human response to these situations, there are cultural differences in the importance of violence. For example, among the Yanomamo of South America, male violence is required to attain status, but among the !Kung San of the Kalahari, aggression only leads to reputational damage.

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