Origin of Human Eyes Traced to 560-Million-Year-Old One-Eyed ‘Cyclops’
Before vertebrates had two eyes, their ancestors may have looked upward with one.
Deep inside the human brain, a small gland in the middle of the forehead helps keep time. As darkness arrives, the pineal gland helps set the body’s nightly rhythm. But some creatures use the pineal gland as a sort of “third eye”, helping them detect light and shadow, though the organ doesn’t form pictures. Our human lineage lost this ancestral ability millions of years ago. In a review published in Current Biology, researchers from Lund University and the University of Sussex argue that the lineage leading to vertebrates passed through a cyclops-like stage roughly 560 million years ago. The animal was not a one-eyed giant, but probably a tiny, wormlike marine filter feeder with a light-sensitive organ on top of its head. As its descendants returned to active swimming, parts of that central organ expanded sideways and were repurposed into paired retinas...
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