A groundbreaking study published in Nature reveals that some of the earliest known vertebrates — dating back around 518 million years — had two pairs of fully functional eyes

The fossils were discovered in China’s Kunming region and belong to early Cambrian jawless fish known as Myllokunmingids . Researchers identified preserved melanosomes and clear lens impressions, confirming that all four eyes were capable of forming images .

Scientists believe the extra pair of eyes gave these ancient vertebrates a wider field of vision, helping them detect predators in prehistoric oceans . Over millions of years, the upper pair is thought to have evolved into the pineal gland — the tiny structure in modern vertebrates that regulates sleep cycles and biological rhythms .