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Cited by 8Animal Behavior and Reproductionmelanin and skin pigmentationHuman-Animal Interaction Studies

The DOI matches its Crossref record; 49 of the 49 references it cites were found in a registry or an index.

Scleral appearance is not a correlate of domestication in mammals

Open access
Caspar, Kai R., Hüttner, Lisa, Begall, Sabine·2023·Zoological Letters
DOI 10.1186/s40851-023-00210-zPMC PMC10228120

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Abstract

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.

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  • There are no differences in scleral phenotypes between domesticated and their wild species.

    “Recently, Caspar et al. [38] tested the hypothesis that the depigmentation of the sclera has been induced by domestication, but there are no differences in scleral phenotypes between domesticated and their wild species.”

    From Are dark-eyed dogs favoured by humans? Domestication as a potential driver of iris colour difference between dogs and wolves (2023) · cites this paper as [38]

    The Results report no statistically significant overall differences in scleral brightness or irido-scleral contrast between domesticated lineages and wild counterparts. But the Results and Discussion also identify pronounced differences in some pairs, including pigs and sheep, so the unqualified claim that there are no differences overstates the finding. Page numbers were not supplied. (LLM, conf=0.88)

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  • A recent study did not support the correlation between depigmentation of the sclera and domestication events.

    “a recent study did not support the correlation between depigmentation of the sclera and domestication events [38].”

    From Are dark-eyed dogs favoured by humans? Domestication as a potential driver of iris colour difference between dogs and wolves (2023) · cites this paper as [38]

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Research works printed but not linked: 1

  1. Rajathi S. Morphological and morphometrical studies of eyeball and retina in goats. Indian J Vet Anat. 2021;33(1):17–9.

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Metadata

Authors
Caspar, K. R., Hüttner, L., & Begall, S.
Affiliations
  • Czech University of Life Sciences Prague (CZ)
  • University of Duisburg-Essen (DE)
Corresponding author
Caspar, Kai R.
ORCID
Venue
Zoological Letters
Publisher
Springer Science and Business Media LLC
Published
2023-05-29
Volume
9
Issue
1
Pages
12-12
ISSN
2056-306X (ISSN-L)
DOI
10.1186/s40851-023-00210-z
PMC
PMC10228120
OpenAlex
W4378697795
Cited by
8
References
49
Citations by year
2026: 2 · 2025: 2 · 2024: 3 · 2023: 1
FWCI
2.03
Type
journal article
Language
en
Update notices
correction (2024-10-28)
Open access
Licence
Locations
  • Zoological Letters (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Heinrich-Heine-Universität Düsseldorf
Topics
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Human-Animal Interaction Studies
Keywords
domestication syndrome, scleral pigmentation, self-domestication, domestic mammals, eye size, marmoset, Carnivora, lagomorphs, ungulates, intraspecific variation

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