Altruistic cooperation, like a typical example of altruistic behavior, is frequently observed in human societies. Since altruistic cooperation; just as any other form of altruism is socially beneficial but individually costly, the evolution of cooperation has long been regarded as a challenging puzzle and one of the most intriguing issues in socio-biological debate. The following three essays analyze these problems. First, I examine the role of institutions in sustaining social norms and the evolution of these institutions. Second, I also analyze the effect of social interactions on the evolution of cooperative traits among individuals where kin selection and reciprocal altruism do not apply. The first essay examines the problems of an n person public goods game structure. In this essay. I show that retaliation based on the repetition of game is not enough to sustain cooperation. By suggesting the difficulties involved in multi-agent interaction and the inapplicability of the repeated game approach to n person public goods situation, the essay reconfirms the importance of institutions that provide favorable conditions for the evolution of cooperation. The second essay analyzes the effect of different structures of social interaction on the evolution of cooperation in an n-person public goods game situation. I set up an agent-based model in which agents interact with others under different social structures, to see which social environment provides favorable conditions for cooperative behavior. In the third essay, I present a model to show how institutions govern relationships and interactions among individuals, and how these institutions evolve. To answer the first question, specifically, I discuss the evolution of equal-sharing norms which had been sustained for most of human history before private property rights were established.