Does Society Need Altruists? Coevolution of General Trust and Social Intelligence

Most social scientists, especially economists, believe that altruists do not exist because they cannot survive exploitation by egoists. An agentbased model demonstrates, however, that altruists can survive natural selection if society comprises four types of individuals: altruists, reciprocal altruists, egoists and reciprocal egoists. These individuals are characterized by different combinations of two phenotypes: general trust and social intelligence. In a society of four types of individuals, coevolution of general trust and social intelligence will emerge. Coevolution constitutes a new mechanism of the emergence of cooperation. If coevolution is strong, altruists will be able to survive and help society evolve into a high-trust and highgrowth society. Without altruists, coevolution does not work and society fails to grow. Thus society needs altruists.