Scientists have determined that all vertebrates, humans included, originated from a one-eyed organism that existed on Earth approximately 600 million years ago.
ALENA YAROVAYA
Biologists from Lund University and the University of Sussex have released a study in the journal Current Biology that fundamentally alters current understanding of visual evolution. According to their findings, the common ancestor of vertebrates was a small, worm-like creature leading a relatively sedentary life, feeding on plankton through water filtration.
The most remarkable feature was that this being possessed only a single light-sensitive structure on its upper body surface. Researchers hypothesize that earlier life forms might have featured paired eyes, but these were lost as the organism adopted a static lifestyle, rendering them redundant. The sole remaining “median eye” served the ancestor’s purpose for distinguishing between daylight and darkness and for spatial orientation.
When vertebrates subsequently resumed more active lifestyles, nature took an economical approach. The new paired eyes developed from components of that very single visual organ. This explains why the human and other vertebrate retina connects directly to the brain, unlike in insects and mollusks, where eye structures evolved from dermal tissues.
A vestige of this ancient “cyclops” remains within our bodies today. A portion of that median eye transformed over evolutionary time into the pineal gland—the epiphysis—which produces melatonin and governs sleep-wake cycles. Therefore, modern humans carry within their brains a relic referring back to an ancestor that lived half a billion years ago.
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