Discuss the role of genetic in human aggression (8+16 marks)
One theory to explain the role of genetics in human aggression is the MAOA hypothesis. The MAOA gene produces the enzyme monoamine oxidase which is responsible for regulating and breaking down serotonin , dopamine and other neurotransmitters at the synapse. A normal MAOA gene produces plenty of this enzyme and constantly breaks down excess serotonin. However, we can be born with a faulty MAOA gene known as MAOA-L. This variant produces far less monoamine oxidase enzyme. This means that that our serotonin levels remain very high in people carrying this variant, as left over serotonin is not being broken down and discarded. These people tend to show increased levels of aggression, because it is thought that the MAOA-L variant leads to the brain being flooded with serotonin and other neurotransmitters. This means that the receptors are constantly active and build up a tolerance to serotonin. So, although these people have more serotonin, it has a very reduced effect. Therefore, human aggression is caused by having a faulty MAOA gene.
To support the claims of the MAOA hypothesis, Brunner et al (the cake) investigated whether genetics play a role in human aggression. He examined a family of 5 males and 5 females from the Netherlands using DNA mapping, with all the males demonstrating high levels of aggression and mental retardation. Their behaviours included, attempted rape and impulsive violence. It was found that all the men had abnormal MAOA genes and produced much less enzymes , consequently causing flawed serotonin metabolism. This in turn led to mental retardation and impulsive aggression . Therefore, this supports the assumption that a faulty MAOA gene can lead to the inability to control aggressive impulses by damaging the serotonin metabolism.
However, Caspi et al (2002) set out to examine the connection between MAOA and aggression in New Zealand. He conducted a longitudinal study following...