The shocking origin of human eyes traces back to an ancient “cyclops”

A bizarre, cyclops-like creature from nearly 600 million years ago may hold the key to how your eyes—and even your sleep cycle—evolved. Scientists have discovered that all vertebrates, including humans, trace their vision back to a single light-sensitive “median eye” perched atop a worm-like ancestor’s head. As this ancient animal shifted from a sedentary to a more active lifestyle, it lost and then reinvented its vision, eventually giving rise to the paired, image-forming eyes we rely on today.