A study looking at the genetic makeup of 895 criminals in Finland has discovered a pair of genes linked with extreme violent behaviour.
The research, carried out by the Karolinska Institute in Sweden and published in the journal Molecular Pyschiatry, compared the genes of non-violent offenders with a group of 78 individuals convicted of violent crimes.
Experts involved in the study say that the majority of violent crime in any society is usually carried out by a small group of repeat offenders who resist attempts at rehabilitation.
The group of 78 were responsible for a total of 1,154 murders, manslaughters, attempted homicides or batteries and the geneticists concluded that between 4 and 10 per cent of all violent crimes in Finland could be traced back to individuals with these genotypes.
All those in the study that had committed murder (including a secondary group of 114 individuals who had all killed at least one person) possessed the MAOA gene, with a variant gene of cadherin 13 or CDH13 also found to be common among violent offenders.
The MAOA gene is sometimes known as the “warrior gene” and is associated with higher levels of aggression in response to provocation, while studies into CDH13 have associated it with substance abusers and low impulse control.
The researchers found that non-violent criminals did not possess these genotypes, concluding that their “findings were specific for violent offending, and not largely attributable to substance abuse or antisocial personality disorder.”
Those involved in the experiments stressed that genetic profiling could not be used to screen for criminals, with Professor Jari Tiihonen telling the BBC: "Committing a severe, violent crime is extremely rare in the general population. So even though the relative risk would be increased, the absolute risk is very low.”
Professor Jan Schnupp of the University of Oxford also cautioned against associating certain genes with violent offences, pointing out that environmental factors have a far greater influence on the chance of an individual being violent.
“Half the people in your office will carry these genes,” he told The Telegraph. “Odds are 50/50 that you do. How violent has your day been? To call these alleles "genes for violence" would therefore be a massive exaggeration.”
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