Human rather than ape-like orbital morphology allows much greater lateral visual field expansion with eye abduction

Denion, É.; Hitier, Martin; Levieil, Eric; Mouriaux, Frédéric

doi:10.1038/srep12437

Cited by 7 publications

(3 citation statements)

References 30 publications

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“…According to Denion et al. (,b), modern humans have more protruding eyes and more rearward lateral orbital margins relative to other hominoids, which are hypothesized to help increase lateral vision in our species. By comparison, Neanderthals and H. heidelbergensis have large and projecting browridges, and their eyes may also have been positioned below these structures, more separated from the neural tissues than what is characteristic of modern humans.…”

Section: Discussionmentioning

confidence: 91%

Shape analysis of spatial relationships between orbito‐ocular and endocranial structures in modern humans and fossil hominids

2017

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The orbits and eyes of modern humans are situated directly below the frontal lobes and anterior to the temporal lobes. Contiguity between these orbital and cerebral elements could generate spatial constraints, and potentially lead to deformation of the eye and reduced visual acuity during development. In this shape analysis we evaluate whether and to what extent covariation exists between ocular morphology and the size and spatial position of the frontal and temporal areas in adult modern humans. Magnetic resonance imaging (MRI) was used to investigate patterns of variation among the brain and eyes, while computed tomography (CT) was used to compare cranial morphology in this anatomical region among modern humans, extinct hominids and chimpanzees. Seventeen landmarks and semi-landmarks that capture the outline of the eye, frontal lobe, anterior fossa/orbital roof and the position of the temporal tips were sampled using lateral scout views in two dimensions, after projection of the average grayscale values of each hemisphere, with midsagittal and parasagittal elements overlapped onto the same plane. MRI results demonstrated that eye position in adult humans varies most with regard to its horizontal distance from the temporal lobes and, secondly, in its vertical distance from the frontal lobes. Size was mainly found to covary with the distance between the eye and temporal lobes. Proximity to these cerebral lobes may generate spatial constraints, as some ocular deformation was observed. Considering the CT analysis, modern humans vary most with regard to the orientation of the orbits, while interspecific variation is mainly associated with separation between the orbits and endocranial elements. These findings suggest that size and position of the frontal and temporal lobes can affect eye and orbit morphology, though potential effects on eye shape require further study. In particular, possible effects of these spatial and allometric relationships on the eye and vision should be examined using ontogenetic samples, vision parameters such as refractive error in diopters, and three-dimensional approaches that include measures of extraocular soft tissues within the orbit.

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Section: Discussionmentioning

confidence: 91%

Shape analysis of spatial relationships between orbito‐ocular and endocranial structures in modern humans and fossil hominids

2017

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“…(2) The human eye socket's outer edge (the temporal orbital margin) is positioned further back [70,71], significantly expanding the temporal visual field. Even a "minor 8.4° anatomical difference results in a large (2.5-fold) difference in maximum temporal visual field eccentricity" [71]. This rear position also allows observers to determine the pupil's position, and thus its line-of-sight, from a wider angle.…”

Section: Act 4: the Curse Of Vodi (Valley Of Darwinian Impossibility)mentioning

confidence: 99%

Darwin’s road not taken: white sclera, shared intentionality, niche construction, predator fear, teams and Homo origins

Skoyles

2023

Preprint

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Palaeoanthropologists have yet to pinpoint how Homo evolved from Australopithecus. I propose niche construction ending predator ambush and stalking attacks, white sclera, and ultrafast team cognition were key.Human white sclera allows the quick, distant detection of line-of-sight. This is unique. In other primates, predators eliminate conspicuous-eyed individuals. Consequently, nonhuman primates have coloured sclera, hiding gaze direction broadcasting. Recognizing line-of-sight split-second from a distance enables the ultrafast detection of attention shifts that support intercoupling cognitions (cognitive alignment, shared intentionality, and split-second coordination). Under certain conditions, such split-second coordinated teams can niche construct predator-shunning safe habitats. Once shunning replaces hunting, it stops white sclera targeting, allowing it to persist.Constructing predator-safe habitats ended the “landscape of fear” that limited Australopithecus foraging, health, and cognitive/cultural development. Once shunned and freed from fear, these safe habitats allowed previously “wheel-clamped” cognitive potentials, including social learning, to flourish, revolutionizing hominin capacity for cultural evolution and cumulative culture. Thus, predator-safe niche construction transfigured Australopithecus’s phenotype into Homo. White-eyed australopiths, I argue, were the first humans.

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“…In humans, the very wide palpebral fissure 16,17 , the rearward-set temporal orbital margin 21,22 and the distinctly forward position of the eyeball in the orbit 23 leave the eyeshell (cornea and sclera) widely exposed to light, even when the eyeball is moved inwards or outwards. Direct or scattered daylight (albedo) 6,8 , results in almost infinite directions of light rays.…”

Section: A Matter Of "Light Through Darkness"mentioning

confidence: 99%

Sclerotic scatter and focusing in eye painting: light through darkness

Denion¹,

Denion²,

Mouriaux³

et al. 2022

ArtSci

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We aimed at searching in color art paintings through all art periods from Ancient Egyptian Art to Contemporary Art for sclerotic scatter (SS) and peripheral light focusing (PLF), using large-scale internet databases. These phenomena originate from the illuminated side of the eyeshell: limbal sclera for SS or cornea for PLF. They end at the darkness of the opposite limbal scleral side, where they are either scattered (SS) or concentrated (PLF) forming a clear arc or spot of light, respectively ("light through darkness"). We found SS and PLF in 83 and 2 paintings respectively out of 113,962 paintings analyzed. These forms of objective chiaroscuro help to reconstruct a basic sense of eyeball modelling by bringing the limbus out of the shadows. Among the paintings with SS, most were painted during the following periods: Renaissance (44), Baroque (15), Rococo (11). Sixty-one of the paintings with SS have a dark background compatible with the fact that SS is more easily observed under low ambient light illuminance ("light through darkness"). Acknowledgment of SS and PLF as subtle, rare characteristics of paintings should help see them in a new light, contribute to their proper treatment and restoration and is likely to enhance their economic value.

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Human rather than ape-like orbital morphology allows much greater lateral visual field expansion with eye abduction

Cited by 7 publications

References 30 publications

Shape analysis of spatial relationships between orbito‐ocular and endocranial structures in modern humans and fossil hominids

Shape analysis of spatial relationships between orbito‐ocular and endocranial structures in modern humans and fossil hominids

Darwin’s road not taken: white sclera, shared intentionality, niche construction, predator fear, teams and Homo origins

Sclerotic scatter and focusing in eye painting: light through darkness

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