School of Psychology and Neuroscience, University of St Andrews, KY16 9JP St Andrews, Scotland;
Max Planck Institute for Psycholinguistics, 6500 AH Nijmegen, The Netherlands.
Proc Natl Acad Sci U S A. 2018 Nov 6;115(45):11393-11400. doi: 10.1073/pnas.1722614115.
Understanding intraspecific variation in sociality is essential for characterizing the flexibility and evolution of social systems, yet its study in nonhuman animals is rare. Here, we investigated whether chimpanzees exhibit population-level differences in sociality that cannot be easily explained by differences in genetics or ecology. We compared social proximity and grooming tendencies across four semiwild populations of chimpanzees living in the same ecological environment over three consecutive years, using both linear mixed models and social network analysis. Results indicated temporally stable, population-level differences in dyadic-level sociality. Moreover, group cohesion measures capturing network characteristics beyond dyadic interactions (clustering, modularity, and social differentiation) showed population-level differences consistent with the dyadic indices. Subsequently, we explored whether the observed intraspecific variation in sociality could be attributed to cultural processes by ruling out alternative sources of variation including the influences of ecology, genetics, and differences in population demographics. We conclude that substantial variation in social behavior exists across neighboring populations of chimpanzees and that this variation is in part shaped by cultural processes.
了解种内社会性变异对于刻画社会系统的灵活性和进化至关重要，但在非人类动物中的研究却很少。在这里，我们研究了黑猩猩是否表现出种群水平的社会性差异，这些差异不能简单地用遗传或生态差异来解释。我们使用线性混合模型和社会网络分析，在三年内比较了生活在相同生态环境中的四个半野生黑猩猩种群的社会接近度和梳理倾向。结果表明，在对偶水平的社会性方面存在时间上稳定的、种群水平的差异。此外，捕捉超越对偶相互作用的网络特征的群体内聚度量（聚类、模块性和社会分化）显示出与对偶指数一致的种群水平差异。随后，我们通过排除包括生态、遗传和种群人口统计学差异在内的替代变异来源，探索了观察到的种内社会性变异是否可以归因于文化过程。我们的结论是，黑猩猩相邻种群之间存在大量的社会行为变异，而这种变异部分是由文化过程塑造的。
