Supplementary Material for: Daily Distance Traveled Is Associated with Greater Brain Size in Primates

Explanations for the brain size increments through primate and, particularly, human evolution are numerous. Commonly, these hypotheses rely on the influence that behavioral and ecological variables have on brain size in extant primates, such as diet quality, social group size, or home range (HR) area. However, HR area does not reflect the time spent moving. As such, it has not been properly addressed whether the effort involved in movement could have affected brain size evolution in primates. This study aimed to test the influence of daily movement on primates’ brain sizes, controlling for these other behavioral and ecological factors. We used a large comparative dataset of extant primate species and phylogenetic comparative methods. Our results show a significant correlation between daily movement and brain mass, which is not explained by the influence of diet, social group size, HR, or body mass. Hence, from an evolutionary timescale, a longer daily movement distance is not a constraining factor for the energetic investment in a larger brain. On the contrary, increased mobility could have contributed to brain mass incrementations through evolution.

学界针对灵长类（尤以人类为代表）演化进程中脑容量扩增的现象，已提出诸多解释假说。此类假说大多基于行为与生态变量对现生灵长类脑容量的调控作用，例如饮食质量、社会群体规模，抑或活动范围（home range, HR）面积。但活动范围面积无法反映物种实际移动所耗费的时长，正因如此，移动过程中的能量付出是否对灵长类脑容量演化存在影响，这一问题尚未得到充分探究。本研究旨在控制上述其余行为与生态变量的干扰，检验每日移动距离对灵长类脑容量的影响。我们使用了涵盖大量现生灵长类物种的比较数据集，并采用系统发育比较分析方法。研究结果表明，每日移动距离与脑质量之间存在显著相关性，且该相关性无法通过饮食质量、社会群体规模、活动范围或体质量的影响进行解释。因此从演化时间尺度来看，更长的每日移动距离并非脑容量扩增所需能量投入的限制因素；反之，移动能力的提升或许在演化进程中推动了脑质量的增加。