Scleral appearance is not a correlate of domestication in mammals

Zoological Letters

Research Article

Sabine Begall¹  Lisa Hüttner¹  Kai R. Caspar² 

[1] Department of General Zoology, University of Duisburg-Essen, Essen, Germany;Institute of Cell Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany;Department of General Zoology, University of Duisburg-Essen, Essen, Germany;Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Praha, Czech Republic;

关键词: Sclera;    Coloration;    Mammals;    Self-domestication;   

DOI  :  10.1186/s40851-023-00210-z

 received in 2023-03-09, accepted in 2023-05-15,  发布年份 2023

来源: Springer

【 摘 要 】

Numerous hypotheses try to explain the unusual appearance of the human eye with its bright sclera and transparent conjunctiva and how it could have evolved from a dark-eyed phenotype, as is present in many non-human primates. Recently, it has been argued that pigmentation defects induced by self-domestication may have led to bright-eyed ocular phenotypes in humans and some other primate lineages, such as marmosets. However, it has never been systematically studied whether actual domesticated mammals consistently deviate from wild mammals in regard to their conjunctival pigmentation and if this trait might therefore be part of a domestication syndrome. Here, we test this idea by drawing phylogenetically informed comparisons from a photographic dataset spanning 13 domesticated mammal species and their closest living wild relatives (n ≥ 15 photos per taxon). We did not recover significant differences in scleral appearance or irido-scleral contrast between domesticated and wild forms, suggesting that conjunctival depigmentation, unlike cutaneous pigmentation disorders, is not a general correlate of domestication. Regardless of their domestication status, macroscopically depigmented conjunctivae were observed in carnivorans and lagomorphs, whereas ungulates generally displayed darker eyes. For some taxa, we observed pronounced intraspecific variation, which should be addressed in more exhaustive future studies. Based on our dataset, we also present preliminary evidence for a general increase of conjunctival pigmentation with eye size in mammals. Our findings suggest that conjunctival depigmentation in humans is not a byproduct of self-domestication, even if we assume that our species has undergone such a process in its recent evolutionary history.

【 授权许可】

CC BY   
© The Author(s) 2023

【 图 表 】

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Fig. 1