Cooperative eye hypothesis Cooperative eye hypothesis The cooperative eye hypothesis is a proposed explanation for the appearance of the human eye. It suggests that the eye's distinctive visible characteristics evolved to make it easier for humans to follow another's gaze while communicating or while working together on tasks. Unlike other primates, human beings have eyes with a distinct colour contrast between the white sclera, the coloured iris, and the black pupil. This is due to a lack of pigment in the sclera. Other primates have pigmented sclerae that are brown or dark in colour. There is also a higher contrast between human skin,
Tache noir de la sclerotique eye, which becomes brown and then black within a few hours, upon which dust settles and the surface becomes wrinkled. Tache noir de la sclerotique Tache noire de la sclerotique (French for "Black spot of the sclera") is one of the ocular signs of death in which a reddish-brown discoloration is transversely arranged across the sclera. It occurs when the eyes are not completely closed so that the sclera is exposed to air. If the eyelids are open for a few hours after death, a film of cell debris and mucus forms two yellow triangles on the sclera, each at