Nearly a century ago, an article appeared in Scientific American making the bold — and, dare I say, "visionary" — prediction that our left eye would become a vestigial organ, endowing us with a single, remaining eye that would possess astonishing powers of perception.
Thomas Hall Shastid, a prominent ophthalmologist and the author of several scientific papers, proposed the theory in 1927. His argument was based upon a premise that the brain's speech center had profoundly effected the development of human vision. He reasoned that, since most people tended to be right-handed (a trait controlled by the left side of the brain), early humans likely relied on their right hand for communication — gestures, accompanied by grunts — that preceded the development of spoken language. Therefore, he argued, the speech center emerged on the left side of the brain, providing the cognitive abilities that made communication with the right hand possible. As such, Shastid concluded, the right eye (which sends visual information to the left side of the brain) became the dominant eye, since detailed vision of the right hand was necessary to enable effective communication. And thus, the left eye became less necessary and began to degenerate.
Shastid expanded upon this convoluted theory to predict our evolutionary destiny:
I believe that, in the course of countless ages, the two human eyes will come closer and closer together, the bridge of the nose will further diminish and sink (just as the animal snout, in man's line of descent, has been doing for vast aeons of time) and, ﬁnally, man's two eyes will become one—just one large, central, cyclopean eye.
It is likely that the merely servient (left) eye will shrink away….so that the right eye will become the cyclopean. Certain it is that the left eye, even today, is being used less and less continually. Man's binocular and stereoscopic visions are being destroyed. That is the price he pays for his speech center.
The great cyclopean eye, however, will regain stereoscopic vision by developing two maculae in the one eye, just in the fashion in which many birds have stereoscopic vision in each eye now. Although the ﬁeld of view will then be narrower than now, the eye will probably be microscopic and telescopic; it will be exceedingly acute for colors, for motion, and for form; and, ﬁnally, most important of all, it will probably be able to perceive as light many forms of energy which now produce in human eyes no sort or kind of perception.
My own theory is that Shastid's research was covertly funded by monocle manufacturers, who were concerned that their eyewear was going out of fashion. (Although, God help us, the monocle might be on the verge of a hipster comeback.) The real shame of it all is that, although we're not becoming cyclopses, we missed a brief evolutionary opportunity to develop a third eye.