THERE is plenty we don’t know about criminal behaviour. Most crime goes unreported so it is hard to pick out trends from the data, and even reliable sets of statistics can be difficult to compare. But there is one thing we do know: those with a biological predisposition to violent behaviour who are brought up in abusive homes are very likely to become lifelong criminals (see “When kids go bad”).
Antisocial and criminal behaviour tends to run in families, but no one was sure whether this was due mostly to social-environmental factors or biological ones. It turns out both…
