Department of Anthropology, University College London, London WC1H 0BW, United Kingdom.
Proc Natl Acad Sci U S A. 2011 Aug 30;108(35):14426-30. doi: 10.1073/pnas.1105186108. Epub 2011 Aug 9.
Recent studies argue that cross-cultural variation in human cooperation supports cultural group selection models of the evolution of large-scale cooperation. However, these studies confound cultural and environmental differences between populations by predominantly sampling one population per society. Here, we test the hypothesis that behavioral variation between populations is driven by environmental differences in demography and ecology. We use a public goods game played with money and a naturalistic measure of behavior involving the distribution of salt, an essential and locally valued resource, to demonstrate significant variation in levels of cooperation across 16 discrete populations of the same small-scale society, the Pahari Korwa of central India. Variation between these populations of the same cultural group is comparable to that found between different cultural groups in previous studies. Demographic factors partly explain this variation; age and a measure of social network size are associated with contributions in the public goods game, while population size and the number of adult sisters residing in the population are associated with decisions regarding salt. That behavioral variation is at least partly contingent on environmental differences between populations questions the existence of stable norms of cooperation. Hence, our findings call for reinterpretation of cross-cultural data on cooperation. Although cultural group selection could theoretically explain the evolution of large-scale cooperation, our results make clear that existing cross-cultural data cannot be taken as empirical support for this hypothesis.
最近的研究认为，人类合作中的跨文化差异支持了大规模合作进化的文化群体选择模型。然而，这些研究通过主要在每个社会中抽样一个群体，混淆了人群之间的文化和环境差异。在这里，我们检验了这样一个假设，即种群之间的行为变异是由人口统计学和生态学方面的环境差异驱动的。我们使用金钱进行公共物品博弈，并使用一种自然主义的行为衡量方法，涉及盐的分配，盐是一种必不可少的、有本地价值的资源，来证明在印度中部的同一个小规模社会——帕哈里·科瓦的 16 个离散种群中，合作水平存在显著差异。同一文化群体的这些种群之间的差异与之前研究中不同文化群体之间的差异相当。人口统计学因素部分解释了这种差异；年龄和社会网络规模的一种衡量标准与公共物品博弈中的贡献有关，而人口规模和居住在该种群中的成年姐妹数量与关于盐的决策有关。行为变异至少部分取决于种群之间的环境差异，这对合作的稳定规范的存在提出了质疑。因此，我们的研究结果要求对合作的跨文化数据进行重新解释。尽管文化群体选择理论上可以解释大规模合作的进化，但我们的研究结果明确表明，现有的跨文化数据不能作为对这一假设的经验支持。
