From “Seven Deadly Sins: The Biology of Being Human” by Guy Leschziner
When it comes to reactive aggression – that impulsive response to threat or frustration, the type of violence that arises in the heat of the moment – it is not just down to testosterone. Genetics also clearly plays an important role. Twin studies – comparing genetically identical twins to non-identical twins, all of whom should have been nurtured in the same environment – suggest that our genes contribute about 40-70 per cent of our aggressive tendencies. Identifying these genetic influences gives us pointers towards the possible chemical underpinnings of this aggression trait.