The eye is an extension of the brain that sits outside the skull. The retina at the back of the eyeball contains about 130 million rod-shaped cells called photoreceptors to deal with black and white and seven million cone-shaped cells to handle color. The x chromosome provides these color cells. Women have two x chromosomes, which give them a greater variety of cones than men, and this difference is noticeable in how women describe colors in greater detail. A man will use basic color descriptions like red, blue, and green, but w a woman will talk of bone, aqua teal, mauve and apple green.
Human eyes have noticeable whites, which other primates lack. This allows for the movement of the eye and the direction of the gaze, which are vital to human face-to-face communication. Women’s eyes display more white than men’s eyes because close-range personal communication is an integral part of female bonding, and more white allows a greater range of eye signals to be sent and received in the direction that the eyes move.
The type of eye communication is not critical to most other species of animal, and so they have little or no whites and rely on body language as the main form of communication.
Women See Wide, Men See Deep
Women not only have a greater variety of cones in the retina, they also have wider peripheral vision than men. As a nest defender, a woman had brain software that allows her to receive an arc of at least 45 degrees clear vision to each side of her head and above and below her nose. Many women’s peripheral vision is effective up to almost 180 degrees. A man’s eyes are larger than a woman’s, and his brain configures them for a type of long-distance tunnel vision, which means that he can see clearly and accurately directly in front of him and over greater distances, almost like binoculars.
A possible explanation: As a hunter, a man needed vision that would allow him to zero in on, and pursue, targets in the distance. He evolved with vision almost like a racehorse with blinders on so that he would not be distracted from targets, whereas a woman needed eyes to allow a wide arc of vision so that she could monitor any predators sneaking up on the nest.