Why Turtles Evolved Shells: It Wasn’t For Protection

The turtle’s shell, then, is a wonderful example of exaptation—the evolutionary process where a trait evolves for one function and is then co-opted to serve another. They began as digging platforms and then became suits of armor. Feathers are another example. They now help birds to fly, but they probably originated as ways of keeping warm or signaling to mates and rivals.