It was suggested that the anxious chimps were pivotal for survival. Outsiders, they were the ones who were sleeping in the trees on the edge, on the border, on the boundary of the community. Hypersensitive and vigilant, the smallest noise freaked them out and disturbed them so they were awake much of the night anyway. We label such symptoms anxiety, but back when we were in trees, they were the early warning system for the troop.
