Close up of a human iris

Brown eye, pupil dilated

Heterochromia, possibly a genetic mosaic

Close up image of a mantis' face (Archimantis latistyla) showing its camouflaged eyes

Blue-eyed black lemur female

Eye color is a visible character caused by two factors: the pigmentation of the eye's iris, and way light is scattered as it hits the top layer of the iris.

The human eye is different from its nearest relative, the chimpanzee eye. The eyes of chimps and also gorillas are entirely brown. Humans have the white to their eyes. This difference is thought to be significant. In the apes, individuals do not usually look directly at other members of the family, but all the same they keep a close watch on what is going on with the family group. They tend to look out of the corners of their eyes, as if to keep the glance secret. Perhaps to them a direct look is aggressive. Jane Goodall used to be careful and avoid looking directly at the gorilla families in the bush. She would sit at a distance, appearing to nibble at grass and leaves, while making occasional glances at the gorilla family.