ABSTRACT
At work people cooperate to carry out tasks which one person could not do alone, and to share the rewards, for example from housebuilding and hunting. In the family there is cooperation of quite different kinds, over the production of children, joint ownership of property, shared eating, and mutual care. Cooperation between friends takes different forms again, largely based on the enjoyment of the relationship, and of various forms of joint leisure, which have no external goals, and no obvious biological purpose. Friends spend a lot of time together, eating and drinking. This is enjoyable in itself, and while they are doing it they provide each other with a lot of help and social support.
