The concept of the third eye transcends its roots in metaphysical yoga, reaching into the realm of scientific discovery.
Researchers have traced the origins of a curious median cornea, hidden deep within our heads, back to our earliest ancestors, who roamed the Earth nearly 600 million years ago. This intriguing revelation, known as the tri-cornea theory, was presented in a groundbreaking study published in the journal Current Biology.
The investigative team embarked on this journey to better understand the pineal gland, a small, pea-sized organ nestled within the human skull. Despite being secluded from sunlight, this gland plays a crucial role in regulating our body’s response to light and darkness.
Present in nearly all vertebrates, ranging from cats to frogs and humans, this third light receptor is responsible for producing melatonin, the hormone essential for managing sleep and wake cycles.
While medical practitioners have acknowledged the “mind’s eye” since ancient times, the origins of this enigmatic organ remained a mystery—until now.
Study author Prof Thomas Baden, a neuroscientist at the University of Sussex and co-author, said that they wanted to find out the “original solution to vision,” as well as the extent to which “different species just copied or modified it to make it their own.”
“What really are the patterns?” he wondered, per the BBC’s Science Focus Magazine. “As you do this over time, you start to wonder, what is the original eye?”
To glean insight into the evolution of our optic organ, the team looked back to one of our earliest ancestors — a small, sea-dwelling maggot from 575 million years ago.
This critter sported two lateral eyes for navigation along with a third lens atop its noggin for monitoring light levels and staying oriented.
This design lasted until around half a billion years ago, when they started burrowing into the sediment, which meant they no longer needed their side eyes to navigate.
In accordance, our subterranean forebears ditched their lateral peepers to conserve resources, effectively leaving them with the third receptor that allowed them to discern up from down and day from night.
This cyclops-like configuration distinguished vertebrates from other lineages, which retained their lateral retinas.
What’s to account for the forward-facing lenses we have today? Eventually, some of the ancestors left the underground and returned to the sea as filter feeders, necessitating tools for navigation — in other words, we needed our eyes back.
Left with no other recourse, parts of the third eye evolved and migrated to the sides of the head, eventually developing into retinas. However, the third eye remained like an evolutionary straggler.
In doing so, they proved that both our retinas and pineal gland evolved from the same ancient organ and not separately as some experts have theorized.
Coincidentally, the study didn’t need to conduct an eye test to shed light on our ocular evolution. They simply reviewed existing scholarship and genetic data from animals such as fish and lampreys to determine how the sight organ’s function in our relatives.
Coincidentally, not all critters’ third eyes are hidden from view.
The tuatara – a bizarre, lizard-like creature from New Zealand – has a sophisticated middle orb situated prominently atop its head like some hybrid monster from Greek mythology.
Much like with humans, this eye is not used for sight, but rather to detect changes between light and dark and use this info to regulate its circadian clock.