Perea-García Juan Olvido, Teuben Aurora, Caspar Kai R
Center for Language Evolution Studies, Nicolaus Copernicus University in Toruń, Fosa Staromiejska 3, Toruń, 87-100, Poland.
University Institute for Health and Biomedical Research (IUIBS), Universidad Las Palmas de Gran Canaria, Las Palmas, Spain.
Biol Rev Camb Philos Soc. 2025 Oct;100(5):2038-2054. doi: 10.1111/brv.70033. Epub 2025 May 14.
The external appearance of the human eye has been prominently linked to the evolution of complex sociocognitive functions in our species. The cooperative eye hypothesis (CEH) proposes that human eyeballs, with their weakly expressed conjunctival and scleral pigmentation, are uniquely conspicuous and evolved under selective pressures to behave cooperatively, therefore signalling attentiveness to conspecifics. Non-human primates are instead assumed to display less-salient eye morphologies that help mask their gaze to facilitate competitive, rather than cooperative actions. Here, we argue that the CEH, although continuing to be influential, lacks robust empirical support. Over the past two decades, multidisciplinary research has undermined its original rationale and central premises: human eye pigmentation does not uniquely stand out among primates, it is not uniform at species level and the available evidence does not conclusively suggest that it facilitates gaze following to notable extents. Hence, the CEH currently provides a theoretical framework that risks confusing, rather than informing, inferences about the evolution of human external eye appearance and its selective drivers. In a call to move past it, we review alternative hypotheses with the potential to elucidate the emergence of the human ocular phenotype from the considerable spectrum of diversity found within the primate order.
人类眼睛的外观与我们这个物种复杂的社会认知功能的进化有着显著的联系。合作眼假说（CEH）提出，人类眼球的结膜和巩膜色素沉着较弱，具有独特的显著性，并且在选择压力下进化以表现出合作行为，从而向同种个体发出专注的信号。相反，非人类灵长类动物被认为具有不太显著的眼睛形态，这有助于掩盖它们的目光，以促进竞争性而非合作性的行为。在这里，我们认为，尽管合作眼假说仍然具有影响力，但缺乏有力的实证支持。在过去的二十年里，多学科研究已经削弱了它最初的理论依据和核心前提：人类眼睛的色素沉着在灵长类动物中并非独一无二地突出，在物种层面上也不统一，而且现有证据并没有确凿地表明它在很大程度上有助于跟随目光。因此，合作眼假说目前提供了一个理论框架，它可能会混淆而不是为关于人类眼睛外观进化及其选择驱动因素的推断提供信息。在呼吁超越这一假说的过程中，我们回顾了其他假说，这些假说有可能从灵长目动物中发现的大量多样性中阐明人类眼部表型的出现。
