For the most part, we’re all products of our genes, the chemical codes that determine how our bodies are made up. That being said, we’re not slaves to our DNA and environmental factors are also known to play a big part. So can we blame certain behaviors, such as the act of committing a violent crime, on the chemistry that we’re born with?

Scientists have been contemplating this for some time, and although it has been suggested that our life experiences probably contribute to around half of the influence, evidence in support of this idea was lacking. But now, a new study on a large bunch of criminals has started to reveal some important genetic clues. After examining the DNA profiles of almost 1,000 criminals, two particular genes were found to be associated with violent, but not non-violent, behaviors. However, it’s important to note that simply possessing this combination of genes does not mean that you are going to commit a crime, and there’s probably a heap of other factors that also play a significant role.

As described in the journal Molecular Psychiatry, to probe whether certain genes could be contributing to the likelihood of committing violent behaviors, researchers looked at the genetic make-up of close to 900 criminals in Finland. The offenders had either committed violent, such as homicide, or non-violent offences. They also took into account environmental factors, such as childhood or substance abuse. After comparing the genetic profiles of these individuals with that of the general population, they identified two particular gene variants that were associated with extremely violent behavior.

One gene, which had a lower than normal activity in the violent offenders, was responsible for a protein called monoamine oxidase A (MAOA), and the other produced a member of the cadherin family, CDH13. The former contributes to the turnover of a molecule called dopamine which plays a major role in addiction and helps control the brain’s reward and pleasure centers. The latter is a sticky cell surface protein that has been linked to substance abuse and ADHD.

According to the study, at least 5-10% of all extremely violent crimes committed in Finland could be attributable to these two particular genotypes. However, these are extremely rare behaviors, and the majority of individuals with this genetic combination won’t go on to commit severe crimes. They also stress that screening for these genes could not be used as a crime-prevention measure and shouldn’t influence convictions.

“There are many things which can contribute to a person’s mental capacity,” lead author Professor Tiihonen told the BBC. “The only thing that matters is the mental capacity of the individual to understand the consequences of what he or she is doing and whether or not the individual can control his or her own behavior.”

[Via Molecular Psychiatry, BBC News and AFP]