In our species the reciprocity principle is the basic ethic behind any society we know: you have to give in order to get, and to reciprocate what you receive. Such is the rule — the expectation or code, if you like — universally (Mauss [1925] 1990; Gouldner 1960; Høgh-Olesen 2006). Or as George Simmel (1950: 387) formulated it: “All contracts among men rest on the schema of giving and returning the equivalence.”

This world's key religious and moral texts are similarly full of stringent requests for sharing and examples of radical self-sacrifices, and modern anthropology's studies of hunter—gatherers' rules of sharing worldwide basically confirm these ethics. Food and resources are shared on the basis of egalitarian and reciprocal principles (Kaplan & Hill 1985; Betzig & Turke 1986; Testart 1987; Lee 1988; Ingold 1988; Hames 2000; Hill 2002), and they are shared on a large scale. Hawkes (1991) has shown that around 84 per cent of a hunter's prey is consumed by others than himself and his nearest family, while 58 per cent of the women's yield is eaten outside the family (Barret et al. 2002: 82).

Bearing in mind the enormous ecological and cultural diversity that otherwise characterizes these societies — and we have data from Arctic areas (Damas 1972), from the South African bush to the Equatorial rainforest (Hart 1978), and from the Australian desert (Gould 1967) — it is thought-provoking that common patterns of sharing even exist.