Data from: Kinship underlies costly cooperation in Mosuo villages

The relative importance of social evolution theories such as kin selection, direct reciprocity and needs-based transfers in explaining real-world cooperation is the source of much debate. Previous field studies of cooperation in human communities have revealed variability in the extent to which each of these theories drive human sociality in different contexts. We conducted multivariate social network analyses predicting costly cooperation—labouring on another household’s farm—in 128,082 dyads of Mosuo farming households in southwest China. Through information-theoretic model selection, we tested the roles played by genealogical relatedness, affinal relationships (including reproductive partners), reciprocity, relative need, wealth, household size, spatial proximity, and gift-giving in an economic game. The best-fitting models included all factors, along with interactions between relatedness and (i) reciprocity, (ii) need, (iii) the presence of children in another household, and (iv) proximity. Our results show how a real-world form of cooperation was driven by kinship. Households tended to help kin in need (but not needy non-kin) and travel further to help spatially distant relatives. Households were more likely to establish reciprocal relationships with distant relatives and non-kin but not with closer kin; closer kin cooperated regardless of reciprocity. These patterns of kin-driven cooperation show the importance of inclusive fitness in understanding human social behaviour.亲缘选择（kin selection）、直接互惠（direct reciprocity）与基于需求的资源转移（needs-based transfers）等社会演化理论，在解释现实世界中的合作行为时的相对重要性，长期以来都是学界争论的焦点。过往针对人类社群合作行为的实地研究表明，在不同情境下，上述理论各自对人类社会行为的驱动程度存在差异。本研究针对中国西南地区128082对摩梭农耕家庭的二元组（dyads）展开多元社交网络分析，旨在预测代价型合作行为——即帮助其他家庭耕作农田——的发生情况。本研究通过信息论模型选择（information-theoretic model selection）方法，检验了谱系亲缘关系、姻亲关系（包括生殖伴侣）、互惠行为、相对需求、财富水平、家庭规模、空间邻近度以及经济博弈中的礼物馈赠等因素的作用。最优拟合模型纳入了所有上述因素，以及亲缘关系与以下变量的交互项：(1) 互惠行为、(2) 需求状况、(3) 其他家庭是否有子女、(4) 空间邻近度。研究结果揭示了亲缘关系如何驱动现实世界中的合作行为：家庭更倾向于帮助有需求的亲属（而非有需求的非亲属），且会跋涉更远的距离帮助空间上距离较远的亲属。家庭更倾向于与远亲及非亲属建立互惠关系，却不会与近亲如此；近亲之间的合作不受互惠行为的影响。这种由亲缘关系驱动的合作模式，印证了广义适合度（inclusive fitness）在理解人类社会行为中的重要性。