Evolutionary explanation of aggression

we change our behaviour in order to increase chances of our genes surviving. E.g.behaving aggressively to prevent infidelity. Genes survive through reproduction and natural selection (Genes that decrease chances of survival are avoided). Therefore aggression is seen as being an effective survival and reproductive technique as it ensures that the fittest are selected and that resources needed for survival are gained and retained.

Jealousy - aggression comes from the major concern of our ancestors to find a mate and reproduce in order to pass on their genes. However, competition between males would cause aggressive behaviour. In order to pass on their genes males had to be sure that their partner was being faithful to them, and therefore male jealousy is seen as an adaptive response that is caused by the threat of infidelity. Men can't be sure they are not the victim of cuckoldry so use mate retention strategies such as direct guarding and negative inducements.

also occurs in females; however the primary concern is not having sufficient resources for the survival of her and her offspring rather than parental uncertainty. 

Buss and Shacklford - mate retention strategies in married couples. They found that men used more threatening behaviour, for example threats to hurt the other man. Men also reported higher levels of debasement (giving in to every wish) as a retention tactic.  

On the other hand women reported using possession signals to indicate to other women that her partner was ‘taken’ and used threats to punish infidelity by leaving her partner. This supports the idea of adaptive behaviour as it is men who are at risk of cuckoldry. However, external validity is reduced as only married couples were tested. Also, a self report method was used which means that results may not be reliable, participants may have lied in order to make their relationship look better (the social desirability effect).

Wilson et al who, using a questionnaire found that women who reported their husbands as the jealous types and don’t want their partner talking to other men were twice as likely to have experienced violence from their partner. This supports the idea of adaptive behaviour as it shows how aggression is used as a mate retention strategy and to reduce the risk of infidelity. However, similarly to the study by Buss and Shaklford, results may lack reliability due to bias results. 

Uses a nature based view - UA is that all behaviour stems from an innate drive for survival and survival of genes. Aggression is therefore seen as inborn rather than havibg any environmental cause such as learned behaviour. It takes a determinist view of aggression, seeing it as an inevitable consequence of mate retention strategies to ensure fidelity in partners.

Cannot form TH - cannot return to evolutionary past where behaviour may have differed. There is, nevertheless, some supporting evidence for the view. Wilson et al

Buss and Shakleford - men used non aggressive mate retention strategies e.g. debasement implying that they excersise an element of free will which contradicts the theories determinist nature thereby reducing effectiveness. Effectiveness is further reduced by the theories inability to explain jealousy and aggression towards couples where the threat of cuckoldry doesnt exist. e.g. infertile/post menopausal women and homosexual male partners.

In addition - buss and shakleford found that mens mate retention strategies were physically threatening when compared to womens who were more likely to threaten to leave their partner. This supports notion of male aggression resulting from fear of cuckoldry as this only affects men.

methodological problems - posibility of research bias both in the way questions were asked and interpreted. 

Also problems come with self reporting and difficulty to operationalise variables such as aggression and jealousy. This therefore highlights a difficulty in regarding psychology as a science as the evolutionary theory cannot be falsified/disproved.

Another problematic aspect is that suggests universality as evolution would affect all cultures, however some cultures do not see infidelty as a problem, and others such as the kung san tribe regard aggression as unacceptable under any circumstances. This reduces effectiveness, especially as the existence of cultural differences suggests the role of environmental factors in behaviour.

HOWEVER - despite all the problems with the theory there is a useful application - mens expression of jealousy can be seen as a early warning sign of future aggression, enabling the action to be prevented . However the theories determinist stance produces ethical problems as it sees jealousy/aggression as inevitable thereby reducing individual responsibilty for things such as domestic violence and provides little contribution to psychology as it provides limited understanding of aggression.