You are reading these words right now because 600 million years ago, an aquatic animal called a Hydra developed light-receptive genes—the origin of animal vision.
It wasn’t exactly 20-20 vision back then though.
Hydras, a genus of freshwater animals that are kin to corals and jellyfish, measure only a few millimeters in diameter and have been around for hundreds of millions of years.
Scientists at the University of California, Santa Barbara studied the genes associated with vision (called opsins) in these tiny creatures and found opsin proteins all over their bodies.
Though they don’t have eyes or any specific light-receptive organs, researchers think that the light-sensing proteins concentrated in the mouth area of the Hydras help them to use light sensitivity to search out prey.