The face is an important visual trait in social communication across many species. In evolutionary terms, there are large and obvious selective advantages in detecting healthy partners, both in terms of avoiding individuals with poor health to minimise contagion and in mating with individuals with high health to help ensure healthy offspring. Many models of sexual selection suggest that an individual's phenotype provides cues to their quality. Fluctuating asymmetry is a trait that is proposed to be an honest indicator of quality, and previous studies have demonstrated that rhesus monkeys gaze longer at symmetric faces, suggesting preferences for such faces. The current study examined the relationship between measured facial symmetry and measures of health in a captive population of female rhesus macaque monkeys. We measured asymmetry from landmarks marked on front-on facial photographs and computed measures of health based on veterinary health and condition ratings, number of minor and major wounds sustained and gain in weight over the first 4 years of life. Analysis revealed that facial asymmetry was negatively related to condition-related health measures, with symmetric individuals being healthier than more asymmetric individuals. Facial asymmetry appears to be an honest indicator of health in rhesus macaques, and asymmetry may then be used by conspecifics in mate-choice situations. More broadly, our data support the notion that faces are valuable sources of information in non-human primates and that sexual selection based on facial information is potentially important across the primate lineage.

中文翻译：

---

面部不对称与雌性猕猴的状况呈负相关


面部是许多物种社会交流中的重要视觉特征。从进化的角度来看，在检测健康伴侣方面存在巨大且明显的选择性优势，无论是在避开健康状况不佳的个体以最大限度地减少传染方面，还是在与健康状况良好的个体交配以帮助确保健康的后代方面。许多性选择模型表明，个体的表型为其品质提供了线索。波动的不对称性被认为是质量的诚实指标，之前的研究表明恒河猴凝视对称面孔的时间更长，这表明它们对此类面孔有偏好。目前的研究调查了圈养的雌性恒河猴中面部对称性测量与健康测量之间的关系。我们测量了正面面部照片上标记的地标的不对称性，并根据兽医的健康和状况评级、小伤口和大伤口的数量以及生命前 4 年的体重增加来计算健康指标。分析显示，面部不对称与状况相关的健康指标呈负相关，对称的人比不对称的人更健康。面部不对称似乎是恒河猴健康状况的真实指标，并且不对称可能被同种猴用于择偶情况。更广泛地说，我们的数据支持这样一种观点，即面部是非人类灵长类动物的宝贵信息来源，并且基于面部信息的性选择在整个灵长类谱系中可能很重要。