Nowak M A, Sigmund K
Department of Zoology, University of Oxford, UK.
Nature. 1998 Jun 11;393(6685):573-7. doi: 10.1038/31225.
Darwinian evolution has to provide an explanation for cooperative behaviour. Theories of cooperation are based on kin selection (dependent on genetic relatedness), group selection and reciprocal altruism. The idea of reciprocal altruism usually involves direct reciprocity: repeated encounters between the same individuals allow for the return of an altruistic act by the recipient. Here we present a new theoretical framework, which is based on indirect reciprocity and does not require the same two individuals ever to meet again. Individual selection can nevertheless favour cooperative strategies directed towards recipients that have helped others in the past. Cooperation pays because it confers the image of a valuable community member to the cooperating individual. We present computer simulations and analytic models that specify the conditions required for evolutionary stability of indirect reciprocity. We show that the probability of knowing the 'image' of the recipient must exceed the cost-to-benefit ratio of the altruistic act. We propose that the emergence of indirect reciprocity was a decisive step for the evolution of human societies.
达尔文进化论必须对合作行为作出解释。合作理论基于亲缘选择（取决于基因关联性）、群体选择和互惠利他主义。互惠利他主义的观点通常涉及直接互惠：同一个体之间的反复相遇使得受惠者能够回报利他行为。在此，我们提出一个新的理论框架，其基于间接互惠，且不要求相同的两个个体再次相遇。然而，个体选择能够青睐针对过去帮助过他人的受惠者的合作策略。合作是有回报的，因为它赋予合作个体有价值的社群成员形象。我们展示了确定间接互惠进化稳定性所需条件的计算机模拟和分析模型。我们表明，了解受惠者“声誉”的概率必须超过利他行为的成本效益比。我们认为，间接互惠的出现是人类社会进化的决定性一步。
