An alternative explanation for the higher incidence of the double Y chromosome in the criminal population was provided. Since the double Y chromosome leads in many cases to mental retardation in affected individuals, it is possible to imagine that criminals carrying the two Y chromosomes might be more susceptible to being caught in the act of commiting a crime. This would lead to a rise in incidence of the double Y chromosome within the inmate population of british prisons. However it would be wrong to conclude that an additional copy of the Y chromosome in men naturally predisposes them to crime. The above example shows that extreme caution must be taken when making conclusions about the role that specific genes play in determining specific behavioural traits both in humans and in other animals.
Genes are only one component of a very complex set of factors that determine behavioural traits.
As already illustrated, epigenetic factors that occur during both foetal and post natal development are also extremely important. Printed with Permission.