Feminism blamed for rising female violence
He says social factors such as the rise of feminism in the last few decades could be behind the rise in violence amongst women.
"We've now taken away the expectation that women will behave differently to men," he said.
"It used to be that one of the biggest differences was that women were more peaceful, they were peacemakers.
"[But] that kind of inhibition to be violent has gradually diminished to the point where it no longer inhibits women at all."