The tendency to commit sex crimes can be inherited and tends to "cluster" in families, an unprecedented study has revealed.
Scientists from the University of Oxford and the Karolinska Institutet in Sweden studied 21,000 convicted paedophiles and rapists in Sweden, in the first large-scale study into whether people are born with the propensity towards rape or child abuse.
They discovered that roughly 40 per cent of the risk of committing a sex crime is genetic, with the remainder attributed to external factors such as whether the perpetrator was a victim of abuse, education, wealth and upbringing, The Daily Telegraph reported.
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Men with a brother who had committed sex crimes were five times more likely to become an offender, while sons were four times more likely. Earlier this year, it emerged that Johnny, the brother of paedophile Jimmy Savile, also raped women in a mental health care unit.
However, researchers found that half-brothers of sex offenders were less likely to commit similar crimes, even if they grew up in the same home. This suggests that their shared environment and upbringing likely had little impact on increasing the risk.
"This does not imply that sons or brothers of sex offenders inevitably become offenders too," said the study's lead author, Niklas Långström. “But, although sex crime convictions are relatively few overall, our study shows that the family risk increase is substantial."
Scientists involved in the study were quick to stress they have not discovered a "sex crime gene" and warned against ostracising male relatives of convicted sex offenders. They did, however, suggest that preventative therapy could be offered to high-risk men to stop crimes before they happen.
"We’re not saying you should lock up the brothers," Oxford University Prof Seena Fazel told The Guardian. "It may well be that something extra can be offered to these high-risk families in terms of teaching about boundary-setting, relationship skills, conflict management.”
Charities working to prevent sexual abuse have welcomed the findings. "The possibility of carefully targeted interventions and support for families in which the relative risks are higher is an exciting prospect," said the National Organisation for the Treatment of Abusers.
Dr Rajan Darjee, a forensic psychiatrist based in Edinburgh, said the findings in no way suggest that a paedophile is "less responsible" for their actions or that offending is inevitable, "it just emphasises that genes are an important part of a complicated jigsaw”.
