Intraspecific eye color variability in birds and mammals: a recent evolutionary event exclusive to humans and domestic animals
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BACKGROUND: Human populations and breeds of domestic animals are composed of individuals with a multiplicity of eye (= iris) colorations. Some wild birds and mammals may have intraspecific eye color variability, but this variation seems to be due to the developmental stage of the individual, its breeding status, and/or sexual dimorphism. In other words, eye colour tends to be a species-specific trait in wild animals, and the exceptions are species in which individuals of the same age group or gender all develop the same eye colour. Domestic animals, by definition, include bird and mammal species artificially selected by humans in the last few thousand years. Humans themselves may have acquired a diverse palette of eye colors, likewise in recent evolutionary time, in the Mesolithic or in the Upper Paleolithic. PRESENTATION OF THE HYPOTHESIS: We posit two previously unrecognized hypotheses regarding eye color variation: 1) eye coloration in wild animals of every species tends to be a fixed trait. 2) Humans and domestic animal populations, on the contrary, have eyes of multiple colors. Sexual selection has been invoked for eye color variation in humans, but this selection mode does not easily apply in domestic animals, where matings are controlled by the human breeder. TESTING THE HYPOTHESIS: Eye coloration is polygenic in humans. We wish to investigate the genetics of eye color in other animals, as well as the ecological correlates. IMPLICATIONS OF THE HYPOTHESIS: Investigating the origin and function of eye colors will shed light on the reason why some species may have either light-colored irises (e.g., white, yellow or light blue) or dark ones (dark red, brown or black). The causes behind the vast array of eye colors across taxa have never been thoroughly investigated, but it may well be that all Darwinian selection processes are at work: sexual selection in humans, artificial selection for domestic animals, and natural selection (mainly) for wild animals.
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Iris colour variation is largely driven by domestication and self-domestication.
“suggesting that iris colour variation is largely driven by domestication and self-domestication [53].”
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 [53]
The Presentation of the hypothesis and Implications of the hypothesis (pages unavailable) link iris-colour diversity in domestic animals to artificial selection, but present this as a hypothesis rather than an established driver. For humans, the paper proposes sexual selection; it does not identify self-domestication as a driver. Thus the claim overstates the proposed explanation and adds a mechanism the paper does not support. (LLM, conf=0.86)
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- Authors
- Negro, J. J., Carmen Blázquez, M., & Galván, I.
- Affiliations
- Estación Biológica de Doñana (ES)
- Corresponding author
- Negro, Juan J.
- Venue
- Frontiers in Zoology
- Published
- 2017-12
- Volume
- 14
- Issue
- 1
- Pages
- 53-53
- ISSN
- 1742-9994 (ISSN-L)
- PMC
- PMC5716259
- OpenAlex
- W2773002681
- Cited by
- 42
- References
- 29
- Citations by year
- 2026: 3 · 2025: 4 · 2024: 3 · 2023: 7 · 2022: 6 · 2021: 7 · 2020: 9 · 2019: 1 · 2018: 2
- FWCI
- 1.75
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by
- Locations
- Frontiers in Zoology (publishedVersion, cc-by)
- Europe PMC (PubMed Central) (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DIGITAL.CSIC (Spanish National Research Council (CSIC)) (acceptedVersion, other-oa)
- LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) (submittedVersion, cc-by-sa)
- DIGITAL.CSIC (Spanish National Research Council (CSIC)) (submittedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
- Funders
- MINECO (RYC-2012-10237, CGL2015-67796-P)
- CONACYT (grant #454959)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic and phenotypic traits in livestock
- Keywords
- eye color, iris color, intraspecific color variation, domestic animals, wild birds, wild mammals, selective breeding, sexual selection, natural selection, polygenic traits, eye color genetics
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