Desmond Morris. The human menagerie (№ 316915)

Fortunately, long-term study of hunting of Sciences contributed to the development of such qualities as ingenuity and willingness to help someone. That's right: the people-the hunters, having, as their ancestors-apes, an innate self-confidence and competitive spirit, was still forced to calm down their militancy and to nominate in the first place, the need for cooperation with each other. This was their only hope to win the battle with long been adapted to everything, armed with sharp claws professional killers (for example, huge cats), which abounded in the carnivorous world. The evolution of human cooperation occurred simultaneously with the development of intelligence and research abilities, and this combination of qualities was simply terrible in its effectiveness.