  Anthropologists have observed gift relationships that establish social
relations as well as the transference of goods in many human societies. The
totality of such social relations constitutes the network. Social scientists
have analysed different types of social organisations with their characteristic
networks. However, the factors and mechanisms that cause the transition between
these types have hardly been explained. Here, we focus on the gift as the
driving force for such changes. We build the model by idealising gift
interactions and simulating the consequent social change due to long-term
massive interactions. We demonstrate the emergence of disparities and various
social organisations depending on the frequency of the gift, consistent with
the empirical data. The constructive simulation study, as presented here,
explains how people's interactions shape various social structures in response
to environmental conditions. Combined with empirical studies, this could
contribute to the formulation of a general theory in the social sciences.
