Scientists have uncovered a surprising possibility about the evolution of human vision: the ancestors of humans and other vertebrates may once have had a single central eye located on top of their heads.

Researchers from Lund University and the University of Sussex suggest that the earliest vertebrate ancestor may have passed through a cyclops-like stage nearly 600 million years ago.

According to the study, this tiny ancient creature had a median eye — a single light-sensitive organ positioned in the middle of its head. Over millions of years, this feature may have played a role in the evolution of the paired eyes found in modern vertebrates, including humans.

The idea challenges traditional assumptions about how complex vision developed. Instead of eyes appearing directly in their current form, researchers suggest that vertebrate vision may have evolved through a series of unusual transitional stages.

The discovery provides new insight into the deep evolutionary history shared by humans, mammals, reptiles, birds, and other vertebrates.

While modern humans have two highly specialized eyes, scientists believe these organs carry traces of an ancient evolutionary journey that began hundreds of millions of years ago with much simpler forms of light detection.

The research highlights how evolution can transform seemingly strange biological structures into features that become essential for survival.