But evolution eventually crossed paths with another possible function: to control the movement of air around the feathered extremities, which allowed a primi-tive form of gliding. This is an example of what paleontologist Stephen Jay Gould called exaptation, by which a trait that evolves in response to an environmental challenge is used for an entirely different purpose (flying).

Exaptations are common in technology as well. The Internet could be analyzed as an exaptation. Designed to enhance communication between scientists, it ended up being adopted by the public as a virtual world that facilitates many kinds of human sharing. Guttenberg’s printing press was based on technologies previously used to crush grapes and make wine. The original function of presses was to crush grapes, and their form was well suited to that function. It just hap-pened that someone eventually saw that the form of those machines could have an entirely different function.