Human beings seem to have a strong impulse to leave their mark. To tell the world that they were here. Unlike other animals we know we’re going to die and leaving some sort of physical mark behind is one way of ensuring our symbolic survival. Of course animals mark their territories too with scent and claw marks, urine and faeces, but humans appear to have an obvious long term intent beyond the marking of territory or the finding of a mate. And perhaps these drives also play their part in our activities.