Abstract Humans usually favour members of their own group, ethnicity or culture (parochial cooperation), and punish out-group wrongdoers more harshly (parochial punishment). The evolution of parochial cooperation is mainly explained by intergroup conflict, as restricting cooperation to in-groups can provide a relative advantage during conflict. However, explanations for the evolution of parochial punishment are still lacking. It is unclear whether conflict can also explain parochial punishment, because conflict is expected to lead to full hostility towards out-groups, irrespective of their behaviour. Here, we use an agent-based simulation to explore which conditions favour the evolution of parochial third-party punishment. We show that when groups interact and then engage in conflict with each other, third-party punishment is not parochial but spiteful, and directed towards all out-groups. A parochial bias in punishment decisions evolves (i) without conflict, when groups compete against nature and enforcing cooperation requires many punitive actions, and (ii) with conflict, when groups come into conflict with a group other than one they previously interacted with. Our findings suggest that intergroup conflict does not always lead to parochial punishment, and that stable collaborative relations between groups is a key factor promoting third-party parochial punishment. Our findings also provide novel predictions on how punishment and intergroup conflict influence in-group bias in human societies.

中文翻译：

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解释人类狭隘惩罚的演变

摘要 人类通常偏爱自己群体、种族或文化的成员（狭隘的合作），而更严厉地惩罚群体外的违法者（狭隘的惩罚）。狭隘合作的演变主要由群体间冲突来解释，因为将合作限制在群体内可以在冲突期间提供相对优势。然而，仍然缺乏对狭隘惩罚演变的解释。尚不清楚冲突是否也可以解释狭隘的惩罚，因为预计冲突会导致对外部群体的全面敌意，而不管他们的行为如何。在这里，我们使用基于代理的模拟来探索哪些条件有利于狭隘的第三方惩罚的演变。我们表明，当群体互动然后彼此发生冲突时，第三方惩罚不是狭隘的，而是恶意的，并且针对所有外部群体。惩罚决策中的狭隘偏见会演变为 (i) 没有冲突，当群体与自然竞争并加强合作需要许多惩罚行动时，以及 (ii) 有冲突，当群体与之前互动的群体以外的群体发生冲突时。我们的研究结果表明，群体间冲突并不总是导致局部惩罚，群体之间稳定的协作关系是促进第三方局部惩罚的关键因素。我们的研究结果还提供了关于惩罚和群体间冲突如何影响人类社会群体内偏见的新预测。当群体与自然竞争并加强合作需要采取许多惩罚措施时，以及 (ii) 冲突时，当群体与之前接触过的群体以外的群体发生冲突时。我们的研究结果表明，群体间冲突并不总是导致局部惩罚，群体之间稳定的协作关系是促进第三方局部惩罚的关键因素。我们的研究结果还提供了关于惩罚和群体间冲突如何影响人类社会群体内偏见的新预测。当群体与自然竞争并加强合作需要采取许多惩罚措施时，以及 (ii) 冲突时，当群体与之前接触过的群体以外的群体发生冲突时。我们的研究结果表明，群体间冲突并不总是导致局部惩罚，群体之间稳定的协作关系是促进第三方局部惩罚的关键因素。我们的研究结果还提供了关于惩罚和群体间冲突如何影响人类社会群体内偏见的新预测。群体之间稳定的协作关系是促进第三方教区惩罚的关键因素。我们的研究结果还提供了关于惩罚和群体间冲突如何影响人类社会群体内偏见的新预测。群体之间稳定的协作关系是促进第三方教区惩罚的关键因素。我们的研究结果还提供了关于惩罚和群体间冲突如何影响人类社会群体内偏见的新预测。