Brothers Karamazov Game, Version 2.

According to the theory of kin selection, an organism that shows some level of altruism toward her kin – lowering her own fitness, raising that of a close genetic relative – may enjoy an evolutionary advantage. Some species show beyond-ordinary altruism toward siblings, and other kin, owing to unusual reproductive biology and/or ecology. Human beings are exceptional in another way: how we treat our kin depends partly on how we feel about them, but also partly on socially enforced norms. This article explores several versions of a simple evolutionary game, the Brothers Karamazov Game, that departs from the standard theory of kin selection to allow for the distinctively human capacity for establishing and enforcing social norms. We discuss possible applications to understanding the “unity of the sibling group” (Radcliffe-Brown) – according exceptional treatment to siblings, and to relatives classified as siblings or linked through siblings. We give special attention to lowland South America, where the sibling relationship is central to social organization.根据亲缘选择（kin selection）理论，若某生物体对其亲属表现出一定程度的利他行为——降低自身的适应度（fitness），同时提升近缘遗传亲属的适应度——则可能获得进化优势。部分物种因特殊的繁殖生物学特征与/或生态环境，对同胞及其他亲属展现出超乎寻常的利他行为。人类则在另一层面具备特殊性：我们对待亲属的方式，既部分取决于自身对亲属的情感联结，同时也部分受到社会强制规范的约束。本文探讨了一款简易进化博弈的多个变体——卡拉马佐夫兄弟博弈（Brothers Karamazov Game），该模型突破了标准亲缘选择理论的框架，纳入了人类独有的建立与执行社会规范的能力。我们还讨论了该模型在理解“同胞群体的统一性”（拉德克利夫-布朗，Radcliffe-Brown）方面的潜在应用——即对同胞、被归类为同胞或通过同胞建立亲属关系的个体给予特殊对待。我们特别关注了南美低地地区，该区域的同胞关系是社会组织的核心组成部分。