Genetic Explanation of Aggression

A gene is a molecular unit of hereditary information. Genes hold the information to build and maintain an organism’s cells, thereby, passing on genetic traits to offspring. The role of genes in some biological traits is understood, and it is argued that some behaviour such as aggression are also passed on in the same way.

One gene said to be associated with aggression is Monoamine Oxidase. This is located on the X chromosome, which triggers the manufacture of the enzyme monoamine oxidase. Its function is to mop up excessive levels of neurotransmitters such as serotonin, dopamine and norepinephrine, rending them inactive. A lack of this enzyme, results in excessive levels of neurotransmitters which it said to be related to aggression.

Our understanding of this explanation is strengthened by research by Rhee and Waldman who carried out a meta-analysis of 87,000 people. They studied anti-social behaviour and categorised them by psychological diagnosis, delinquency and behavioural aggression. They found that the genetic component for aggression was roughly 40% with the environment, and other biological factors were 60%. This suggests that genetics does play a role in the development of aggression, and therefore, strengthens the genetic explanation.

The genetic explanation is further strengthened by research by McGuffin and Gottesman who carried out twin studies with MZ’s and DZ’s. They studied the concordance rates for anti-social behaviour and aggression and found that the MZ’s had an 87% concordance rate, whilst the DZ’s had 72%. As the concordance rate for the MZ’s is slightly higher, it suggests that genes do play a part in aggression and, therefore, strengthens the genetic explanation.

The degree to which the genetic explanation is successful in explaining aggression is also strengthened by researchers who studied mice lacking in MAOA. They found that those were lacked the functional gene, that they had increased aggression towards intruder mice...