The particular colors on an animals are determined partly by the genes its gets from its parents. That means that genes that hide animals can spread thanks to natural selection, leading to the evolution of exquisite camouflage. But that’s not to say that the animal kingdom has settled on a perfect, fixed palette. You can find mismatched individuals. Over the course of generations, a whole population can flicker between mismatched and well-matched.

The most famous example of mismatched colors first came to light in the 1950s. Coal smoke had darkened England’s trees, so that light pepper moths, once blended nicely against bark, now stood out against the smudgy background. A dark form of peppered moths, once rare, became common. Researchers suspected that natural selection was the reason why, and they tested that idea by putting dark and light moth models on trees. Birds quickly attacked the mismatched ones, as had been predicted.

The photos from these experiments became a staple of textbooks. But doubts arose about the research. Real peppered moths often don’t sit on tree trunks with wings extended, for example. Creationists called the whole phenomenon a fraud and a reason to question evolution itself.