This chapter aims to consider how deep reciprocity lies in humans, by looking at some of the evidence on how tribal communities live. Although extant tribal communities have invariably been touched by the modern world, they perhaps offer a reasonable approximation of the practices conducted in human hunter-gather societies for tens of thousands of years. Reciprocity – in both its positive and negative forms – is of fundamental importance to the functioning of tribal communities. Here, people reciprocate over almost everything – e.g. through sharing meat, childcare responsibilities, wisdom etc. – and within and between communities, gifts are used to bind and obligate. Moreover, the threat of negative reciprocity discourages the transgression of social norms and attempts to exert power. In tribal communities, it is likely that reciprocity evolved organically for the good of the group, but as societies became larger and more atomised, creating opportunities for people to act on egoistic motivations with less fear of detection, a form of social contract was perhaps needed to nurture and sustain the socially beneficial norm of reciprocity.