evolutionary explanations of human aggression

• Evolutionary explanations of human aggression propose that aggression serves an important function in terms of both the individual's survival as well as their reproductive success. Evolutionary theories propose the human brain is the product of evolutionary pressures and a number of adaptations have occurred to cope with the challenges of survival. 
• Aggression is therefore seen as an adaptive response to help solve a number of problems an individual may face such as the need for resources through intimidation or elimination of rivals to secure access to females and reproduce. When such resources are in scarce supply aggression is seen as more likely as it helps deal with such a situation and compete.
• One way aggression is seen as an adaptive response is when it is used in sexual competition with other males to get access to females. Physical aggression allows the elimination of rival males and such individuals are then more likely to attract females (who see it as a sign of genetic fitness) and be successful in reproducing and passing on their aggressive genes.
• Females tend to have stricter methods for choosing a mate and need to consider the needs of any potential children over the long-term. A potential partner is then judged based on their ability to supply resources and aggression is seen as one method by men to achieve this. 
• Over time this would have led to the development of future generations more genetically prone to being aggressive to other males through these evolutionary pressures to compete. This is supported by the fact that men have 75% more muscle mass than women (Lassek et al 2009), are more aggressive than females and more likely to die violently (Buss 2005). Anthropological evidence also supports this men have universally thicker jawbones and more robust skulls than women which Puts (2010) argues is evidence of male traits that imply competition with other males did occur throughout our ancestry.
• Another evolutionary explanation of human aggression concerns sexual jealousy which arises due to paternal uncertainty (Archer 2013). Unlike women, men can never be sure that they are the fathers of their children however women are always certain of maternity as they give birth to them. Due to this men are always at the risk of cuckoldry and raising a child that is not their own due to their partners infidelity. This results in a man unknowingly investing his time and resources on children that are not his own preventing him from successfully passing on his genes.
• Sexual jealousy is therefore an adaptive response to deter partners from sexual infidelity to minimise the risk of cuckoldry and may be exhibited through aggression. A number of aggressive strategies have evolved by men to keep a mate which involve violence, the use of threats or violence towards partners to prevent them leaving as well as towards potential new partners (Buss 1988).
• Other explanations look at aggression in warfare. War is costly and places individuals at extreme personal risk however evolutionary explanations propose it also adaptive. For example Livingstone Smith (2007) proposes that warfare originated not only to obtain valuable resources but also to attract mates and forge intragroup bonds. Aggressive displays and bravery are thought to be attractive to females and increases the chances of obtaining a mate.
• Chagnon (1988) found that male warriors in traditional societies tended to have more sexual partners and children suggesting it did have a reproductive benefit. Aggression in combat and war is also believed to increase status and lead to greater respect among social groups which would also lead to greater reproductive fitness and access to more resources.