What is the “third eye”? Is it a mystical part of the brain that acts as a gateway to a higher consciousness? Is it a cheap cliche used by hackneyed slam poets? Well, yes… at least to the last one. The concept of a “third eye” dates back thousands of years in the Hindu tradition, as a literal and figurative organ which allows one to “see” the future, auras, and the face of true knowledge. But before you start trying to access your sixth chakra to achieve clairvoyance, it might be helpful to talk to an animal that actually has a third eye, and ask it what it’s good for.
I will make your head explode with my mind.
The tuatara, a reptile endemic to New Zealand, is a curiosity in every right. Though it looks like a lizard, it’s not; its lineage can be traced back to the age of dinosaurs, far before the modern lizards and snakes. It is the only survivor of the genus Sphenodontia, which had its heyday 200 million years ago, and has been hiding out with the kiwis ever since. Tuataras have an incredibly slow metabolism which has two main effects: they are the slowest-growing reptiles, needing about 65 years to reach their maximum size, and they also tolerate cold better than any other reptile. Their optimum temperature is between 60-70 degrees F, but they still function at a chilly 40 degrees F. Their ears have no earholes nor eardrums, and their teeth are not separated, but rather two interlocking bandsaws of bone. But the strangest thing about their anatomy may be the hidden eye on their forehead.
It’s called the parietal eye, and it’s actually not all that uncommon, being found in many lizards, frogs, salamanders, sharks, and bony fish. But it’s far more developed and pronounced in the tuatara, containing a lens, a cornea, a retina (with rod-like cells) and a primitive optic nerve connecting it to the brain. The parietal eye is invisible on adult tuatara, covered over by skin and scales, but is visible on juveniles under 4 months old. Scientists aren’t sure exactly what role the parietal eye plays in survival, but they have some good leads. It is photoreceptive, and may help tuatara detect a threat from above by its shadow alone. If it can perceive polarized light, as it does in amphibians, it might also be useful in navigation. The parietal eye may also regulate circadian rhythms by triggering the release of melatonin at night. This theory is borne from the fact that there’s an melatonin-producing organ within the mammalian brain whose cells strongly resemble those of the retina: the pineal gland.
The pea-sized pineal gland has been the source of much superstition and speculation throughout the history of anatomy. It occupies prime real estate in the midbrain, yet we’re not completely certain what it does. It produces the melatonin which seems to regulate wake/sleep patterns and keep our circadian and seasonal rhythms in synch, which is important, but the pineal gland also has the propensity to calcify when we become adults. Some theories hold that melatonin inhibits sexual development and puberty, which is why the pineal gland is larger and more active in children. Rene Descartes called the it “the seat of the soul,” and modern occultists still consider it the source of all supernatural powers; when “activated,” it supposedly allows you to see through time, receive messages from the realm of wraiths, or communicate with the chaos goddess Eris.
In actuality, it just makes you sleepy and keeps you from growing pubic hair.
But is there a connection between the tuatara’s external third eye and the pineal gland, which is seated in the center of the brain? There is some evidence from the rare fossilized brain of an ancient bird. Brains don’t fossilize well, being made of squishy gray matter, mostly, but amazingly, the brain of a Melovatka bird, an archaeopteryx nephew from 90 mya, was found perfectly preserved in Russia. More amazingly, it had both a pineal gland, which modern birds have, and a parietal eye, which they lack. This suggests that the two organs are separate, but isn’t conclusive. It’s possible the gland and the eye split functions, doing the dual duties of sensing night and day and regulating sleep patterns. Seeing as many of the oldest reptilian fossils had an actual socket for their third eye, whereas none do today, the evidence suggests that the function, if not the organ, retreated deep into the gray matter.
Tuatara today are critically endangered, another casualty of human conquest of paradise. They number a mere 60-100,000, surviving mostly on a series of tiny satellite islands the Polynesian rats haven’t yet managed to reach. If tuatara or their ancient, three-eyed ancestors ever had psychic powers, they seemed to have failed them. When it came to the two great asteroids of the past 65 million years — Chicxulub, the dinosaur-slayer, and the extinction event called humanity — it seems they never saw it coming.