More than half a billion years ago a spectacularly creative burst of biological innovation called the Cambrian explosion occurred. In a geologic “instant” of several million years, organisms developed strikingly new body shapes, new organs, and new predation strategies and defenses against them. Evolutionary biologists disagree about what triggered this prodigious wave of novelty, but a particularly compelling hypothesis, advanced by University of Oxford zoologist Andrew Parker, is that light was the trigger. Parker proposes that around 543 million years ago, the chemistry of the shallow oceans and the atmosphere suddenly changed to become much more transparent. At the time, all animal life was confined to the oceans, and as soon as the daylight flooded in, eyesight became the best trick in the sea. As eyes rapidly evolved, so did the behaviors and equipment that responded to them.