Pre-publication draft; please do not quote or circulate. P. Gray, Play in Hunter-Gatherers p 28
tendency to play. Hunter-gatherers’ existence apparently required an intense kind of long-term sharing, which was not based just on blood relationships or direct reciprocity. Such sharing would be destroyed by dominance. Dominance induces fear and anger, while play induces unity and friendship. The kind of sharing upon which hunter-gatherers depended apparently required the feelings of unity and friendship that play can produce. Therefore, to survive, hunter-gatherers everywhere developed cultural practices designed to maximize their playful tendencies and minimize their dominance tendencies.
In addition to the cultural adaptations, it is quite possible that further biological adaptations enabled hunter-gatherers to develop, over time, ever more playful approaches to social life. If we assume that the needs for intense sharing were present for hundreds of thousands of years in our human and human-like ancestors, then natural selection could well have expanded and elaborated upon the play instincts inherited from our earlier primate ancestors. In most mammals, including most primates, play occurs mostly among the young and apparently serves primarily the function of education. Young mammals practice, in play, the skills they must develop for survival into and through adulthood. In some primates, play may also serve a bonding function, helping to counteract the fear induced by dominance systems and thereby helping to promote cooperation. This may help explain why, in some primates, social play is observed to some degree among adults as well as among juveniles.83 A great increase in the need for cooperation and sharing based on friendships could have led to further expansion of the human play drive into adulthood and to an increased flexibility of that drive, allowing it to be applied in a wider variety of contexts and be manifested in an essentially infinite variety of activities.