600-Million-Year Cyclops Traced as Progenitor of Vertebrate Vision
New research links vertebrate vision to a 600-million-year-old wormlike ancestor that had a single median eye. Over time, that eye’s light-sensing cells organized into the modern image-forming eyes, while the pineal gland remains a direct descendant; this explains why vertebrate retinas develop from brain tissue and why insect and squid eyes originate from skin.