Lotem Arnon, Fishman Michael A, Stone Lewi
Department of Zoology, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel.
Proc Biol Sci. 2003 Jan 22;270(1511):199-205. doi: 10.1098/rspb.2002.2225.
Cooperation among genetically unrelated individuals is commonly explained by the potential for future reciprocity or by the risk of being punished by group members. However, unconditional altruism is more difficult to explain. We demonstrate that unconditional altruism can evolve as a costly signal of individual quality (i.e. a handicap) as a consequence of reciprocal altruism. This is because the emergent correlation between altruism and individual quality in reciprocity games can facilitate the use of altruism as a quality indicator in a much wider context, outside the reciprocity game, thus affecting its further evolution through signalling benefits. Our model, based on multitype evolutionary game theory shows that, when the additive signalling benefit of donating help exceeds the cost for only some individuals (of high-quality state) but not for others (of low-quality state), the population possesses an evolutionarily stable strategy (ESS) profile wherein high-quality individuals cooperate unconditionally while low-quality individuals defect or play tit-for-tat (TfT). Hence, as predicted by Zahavi's handicap model, signalling benefits of altruistic acts can establish a stable generosity by high-quality individuals that no longer depends on the probability of future reciprocation or punishment.
基因不相关个体之间的合作通常被解释为未来互惠的可能性或被群体成员惩罚的风险。然而，无条件利他主义更难解释。我们证明，作为互惠利他主义的结果，无条件利他主义可以作为个体质量的一种代价高昂的信号（即一种障碍）而进化。这是因为互惠博弈中利他主义与个体质量之间出现的相关性可以促进利他主义在互惠博弈之外的更广泛背景下作为质量指标的使用，从而通过信号传递益处影响其进一步进化。我们基于多类型进化博弈理论的模型表明，当提供帮助的附加信号传递益处仅对某些个体（处于高质量状态）超过成本，而对其他个体（处于低质量状态）则不然时，种群拥有一种进化稳定策略（ESS）分布，其中高质量个体无条件合作，而低质量个体背叛或采取针锋相对（TfT）策略。因此，正如扎哈维的障碍模型所预测的，利他行为的信号传递益处可以建立起高质量个体稳定的慷慨行为，这种行为不再依赖于未来互惠或惩罚的概率。
