The adaptive significance of human scleral brightness: an experimental study
Open accessAbstract
Homogeneously depigmented sclerae have long been proposed to be uniquely human—an adaptation to enable cooperative behaviour by facilitating interpersonal coordination through gaze following. However, recent evidence has shown that deeply pigmented sclerae also afford gaze following if surrounding a bright iris. Furthermore, while current scleral depigmentation is clearly adaptive in modern humans, it is less clear how the evolutionarily intermediate stages of scleral pigmentation may have been adaptive. In sum, it is unclear why scleral depigmentation became the norm in humans, while not so in sister species like chimpanzees, or why some extant species display intermediate degrees of pigmentation (as our ancestors presumably did at some point). We created realistic facial images of 20 individually distinct hominins with diverse facial morphologies, each face in the (i) humanlike bright sclera and (ii) generalised apelike dark sclera version. Participants in two online studies rated the bright-sclera hominins as younger, healthier, more attractive and trustworthy, but less aggressive than the dark-sclera hominins. Our results support the idea that the appearance of more depigmented sclerae promoted perceived traits that fostered trust, increasing fitness for those individuals and resulting in depigmentation as a fixed trait in extant humans.
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White sclera is positively correlated with attractiveness, trustworthiness and low aggressiveness.
“white sclera positively correlated with attractiveness, trustworthiness and low aggressiveness [42]”
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 [42]
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- Authors
- Wacewicz, S., Perea-García, J. O., Lewandowski, Z., & Danel, D. P.
- Affiliations
- Wroclaw University of Health and Sport Sciences (PL)
- Ludwik Hirszfeld Institute of Immunology and Experimental Therapy (PL)
- Venue
- Scientific Reports
- Published
- 2022-11-24
- Volume
- 12
- Issue
- 1
- Pages
- 20261-20261
- ISSN
- 2045-2322 (ISSN-L)
- PMC
- PMC9691750
- OpenAlex
- W4310057238
- Cited by
- 18
- References
- 70
- Citations by year
- 2026: 6 · 2025: 5 · 2024: 3 · 2023: 2 · 2022: 2
- FWCI
- 2.76
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Scientific Reports (publishedVersion, cc-by)
- Research Square (acceptedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Leiden Repository (Leiden University) (submittedVersion, cc-by)
- Acceda (Universidad de Las Palmas de Gran Canaria) (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Data Archiving and Networked Services (DANS) (submittedVersion, cc-by)
- Topics
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Evolutionary Psychology and Human Behavior
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
- Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
- Keywords
- scleral pigmentation, facial appearance perception, gaze following, interpersonal trust, facial attractiveness, chimpanzees, adaptive evolution, social cognition
- MeSH terms
- Animals, Pan troglodytes, Humans, Iris, Pigmentation, Sclera, Hominidae
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