Department of Biological Sciences, National University of Singapore, Singapore, 117557, Singapore.
Institute of Psychology, Cognitive Psychology Unit, Leiden University, Wassenaarseweg 52, 2333 AK, Leiden, The Netherlands.
Sci Rep. 2022 Oct 15;12(1):17240. doi: 10.1038/s41598-022-20900-6.
External eye appearance across primate species is diverse in shape and colouration, yet we still lack an explanation for the drivers of such diversity. Here we quantify substantial interspecific variation in eye shape and colouration across 77 primate species representing all extant genera of anthropoid primates. We reassess a series of hypotheses aiming to explain ocular variation in horizontal elongation and in colouration across species. Heavier body weight and terrestrial locomotion are associated with elongated eye outlines. Species living closer to the equator present more pigmented conjunctivae, suggesting photoprotective functions. Irises become bluer in species living further away from the equator, adding to existing literature supporting a circadian clock function for bluer irises. These results shift the current focus from communicative, to ecological factors in driving variation in external eye appearance in anthropoid primates. They also highlight the possibility that similar ecological factors contributed to selection for blue eyes in ancestral human populations living in northern latitudes.
灵长类动物的眼睛在外貌上呈现出多样化的形状和颜色，但我们仍然缺乏对这种多样性驱动因素的解释。在这里，我们量化了 77 种灵长类物种的眼睛形状和颜色的大量种间变异，这些物种代表了所有现生的人科灵长类动物属。我们重新评估了一系列旨在解释水平伸长和物种间颜色变化的假说。较重的体重和陆地运动与拉长的眼睛轮廓有关。生活在赤道附近的物种的结膜色素沉着更多，表明具有光保护功能。虹膜在远离赤道的物种中变得更蓝，这增加了支持蓝眼睛具有昼夜节律钟功能的现有文献。这些结果将当前的研究重点从交流因素转移到了生态因素，这些生态因素驱动了人科灵长类动物外部眼睛外观的变化。它们还突出表明，类似的生态因素可能促成了生活在高纬度地区的人类祖先群体中对蓝眼睛的选择。
