of genetics to anti-social behaviour. Now, most scientists would accept that genes control much of who we are, but the potential for science to at least partially produce a genetic explanation for problematic behaviour, inevitably has significant implications for policy development, particularly in areas such as law and public health. But what actual evidence is there that genes may actually predispose a person to criminal behaviour? One of the better-known theories is that of ‘Supermale Syndrome’. Here the ‘supermale’ possesses an extra Y chromosome, so instead of the usual XY, he is XYY. This is a common condition; 1 in 1000 newborn males are supermales – 0.1% of the male population. Many studies attempted to prove that there was a direct link between increased aggressiveness and the extra Y chromosome. These have been inconclusive. However, what was shown was that XYY men are less intelligent and possess an IQ lower than the average person. This led to suggestions that because of their diminished capacity for learning, fewer supermales complete High School, and therefore are more likely to become criminals. There were numerous studies conducted during the sixties within prisons in an attempt to validate the correlation between the extra Y chromosome and criminal behavior. One team of scientists conducted a study at the maximum-security state hospital in Carstairs, Scotland. 3.5% of the males in the prison were supermales — 35 times the average of 1 in 1000. Further research has since ascertained that men who carry the extra Y chromosome are unable to metabolise three important neurotransmitters, namely dopamine, norepinephrine, and serotonin. Why? Because the enzyme MAOA, which normally metabolises these neurotransmitters, is disabled. Neurotransmitters regulate behaviour in specific parts of the brain, and any deficiency can seriously
VIVID 3rd Edition May 2008
affect mental health. This often makes the individual less capable of controlling emotions and impulses. The sampling methods used in this prison survey have since been discredited, but the theory on MAOA has not. In another study they found a tiny mutation in the structural gene for MAOA which was associated with the aggressive criminal behaviour of a number of males in a certain family. These males had selective MAOA deficiency, which may lead to decreased concentrations of 5-HIAA in cerebrospinal fluid. Low concentrations of 5-HIAA can be associated with impulsive aggression. Evolutionarily, traits of aggression and selfishness would have been valuable to a male concerned with group dominance; now such impulses are socially suppressed. Much of the evidence to promote the importance of the environment
“genetic theories of criminality were quickly discredited after World War II, due to their unsavoury association with eugenics and Nazi ‘criminal biology’” in the creation of a criminal comes from twin studies. However, whereas as one prominent study found that there is a 54% heritability factor for tendency to criminality, another found little or no heritability factor. The disparity arises from difficulty in the interpretation of the boundaries of nature and nurture, a debate which although it does not polarise scientific opinion, still leads to biased interpretation of data. Nevertheless, the majority of studies on the influence of the environment show a correlation between families with poor communication and weak bonds and the development
of aggressive or criminal behaviour in children. This leads many to conclude that those families which are less financially sound, that perhaps have more children, and that do not consistently punish their children, will have a greater likelihood of creating an environment that will influence criminal behaviour. Abuse or neglect in childhood can also have great bearing. One study showed that children are at a 50% greater risk of engaging in criminal acts if they suffered this kind of treatment. The debate is no longer about whether or not genes play a role in criminality, rather how much of a role they play. Research has indicated that it is an interaction between genes and the environment which leads to criminal behaviour — the struggle is now to assert the boundaries of the two factors. There is certainly no such thing as an isolatable criminal gene, though gene variants such as the MAOA example or certain combinations of gene variants, play their role in criminal tendencies. It is important to remember that having a genetic predisposition for criminal behaviour does not determine the actions of an individual. However, if they are exposed to the wrong environment, then the likelihood of their engaging in criminal behaviour is increased. V
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