Why are most violent crimes, such as assault or murder, committed by a minority of people who are also repeat offenders? To answer this question, a group of neuroscientists from the Karolinska Institute in Sweden analyzed the DNA of 800 inmates in Finland, and found that individuals convicted multiple times of offenses related to aggression possessed at least one of the following genetic variants s : CDH13 and MAOA.
The latter, also known as the ' warrior gene ', controls the production of a neurotransmitter called dopamine. If its activity decreases, and the carrier also consumes alcohol, cocaine or amphetamines, an explosion of dopamine occurs that can potentially lead to the commission of violent crimes.
For its part, CDH13 encodes a neuronal cohesion protein that contributes to the connections of nerve cells in the brain. People with both variants, according to the researchers, are up to 13 times more likely to commit a violent crime.
The study also clarifies why the majority of serial killers are men. Since MAOA is on the X chromosome, having a faulty allele or version of the gene has a remedy in the case of women, who have two of these chromosomes. In contrast, men, with a single X chromosome, would lack a spare.
