Recent research published in Current Biology has shed light on the evolutionary origins of the human 'third eye,' tracing it back to a small, sea-dwelling ancestor from approximately 575 million years ago. This creature possessed two lateral eyes for navigation and a third lens on its head to monitor light, which was crucial for its survival. As the ancestor evolved and adapted to a subterranean lifestyle, it lost its lateral eyes but retained the third eye, which helped it discern light and orientation. Over time, as some descendants returned to aquatic environments, parts of this third eye evolved into the retinas we have today. The study, led by Prof. Thomas Baden from the University of Sussex, also highlights the role of the pineal gland, which continues to regulate sleep through melatonin production. Interestingly, the tuatara, a lizard-like species from New Zealand, retains a visible third eye that serves a similar function in regulating its circadian rhythms.