evolutionary theory

Evolutionary theory claims that aggression is ‘built in’ to human nature because in our evolutionary history it was adaptive (useful).

One reason for accepting this idea is because aggression is universal in human societies (it appears everywhere). Intraspecies aggression (e.g. human aggression against other humans) seems to be a feature of humans that makes us different from other species.
Evidence to support this view comes from Gomez et al (2016) who compared lethal intraspecific violence in 1024 mammal species and 600 human populations. They found that the death rate in the non- humans was about 0.3% but in humans it was 2%.
They conclude that the uniquely high death rate from intraspecific violence in humans is a consequence of our evolutionary history and that aggression is there because individuals who were aggressive against other humans were more likely to survive and reproduce than less aggressive individuals.

Evolutionary theory claims that aggression evolved because it helps individuals to compete for resources like food.

A reason for accepting this claim is that many species become more aggressive when resources are scarce. As evidence for this, Lorenz (1966) observed that when food supplies are reduced, many species become more active in marking and defending territory and become more ready to attack conspecifics (members of the same species).
In addition, Allen et al (2016) correlated environmental conditions over long periods with archeological evidence from prehistoric graves. They found that in times of famine or drought there was more evidence of violent death (e.g. sharp force trauma on bones). This suggests that, throughout history, there is a relationship between scarcity and violence that supports the evolutionary view.

Evolutionary theory claims that aggression evolved because it helps secure the survival of the individual’s offspring.

A reason for accepting this view is that there are many human and animal behaviours that serve to obtain access to mates and limit the access of others to the individual’s mate. Evidence for this comes from many studies.
Puts et al (2016) observes that human males are larger and more aggressive than females, suggesting that human males evolved to use aggression to compete with other males.
Other studies have found that men are more bothered by sexual infidelity than women (Buss, 2000) and that intimate partner violence is often precipitated by a man’s fear of infidelity or of losing his partner.
These findings are consistent with the idea that aggression in human males serves to increase the likelihood that the offspring a father rears carry his genes and not someone else’s.

There are a number of reasons people might reject the claims of evolutionary theory.

First, it is possible that aggression is learned rather than innate. Children who are exposed to aggressive behaviour seem to become more aggressive themselves.
- In support of this, Bandura et al (1962) found that children would readily imitate aggressive acts they had seen an adult perform against an inflatable doll, if given the opportunity to do so.
Other critics have pointed out that most of the evidence in support of evolutionary theories is correlational, and therefore does not show a causal relationship.
- For example, there is a correlation between droughts/famines and evidence of violent death in the historical record. This might be because food scarcity makes people more aggressive or it might be because more evidence of violent deaths survives from those times because the climate/environment was different (e.g. colder, drier).
Feminist critics have suggested that evolutionary explanations of aggression are not really scientific and function more as ways of justifying male violence against women by casting them as natural and inevitable.