For most animals the struggle to survive takes up all their time. Finding food and drink, keeping warm and clean, avoiding predators, migrating and reproducing use up all their energies. If they do have any time to spare, they spend it resting or sleeping. Only very young animals, under the protection of their parents, have enough surplus energy to engage in lively bouts of play. This was also true for our early ancestors. The constant search for food would have put heavy demands upon them. But as they slowly evolved into more and more efficient hunters, the situation changed. The secret of their success was the development of much greater intelligence. They used brain not brawn to kill their prey. At the end of the long hunting era, before they turned to farming, they were already enjoying some degree of affluence. In certain regions, at particular times of year, the prey was sufficiently plentiful and their hunting techniques sufficiently advanced for them to experience a remarkable degree of prosperity. They had time on their hands.