The instinct that has worked for 100 million years
Sea turtle hatchlings emerge from their sandy nests at night and face an immediate problem: they have never seen the ocean. They find it anyway, almost every time, using a behaviour called positive phototaxis. Under a natural night sky, the open ocean is the brightest thing on the horizon, moonlight and starlight reflect off the water's surface, while inland vegetation and dunes block light and create a darker silhouette. The hatchlings move toward the brightest light source. For roughly 100 million years, that instinct reliably delivered them to the water within minutes of hatching.
