One of the key ideas in modern evolutionary theory is that of preadaptation. The term may sound oxymoronic but its significance is perfectly logical: every feature of an organism, in addition to its obvious functional characteristics, has others that could become useful in totally novel ways under the right circumstances. The forerunners of air-breathing lungs, for example, were swim bladders with which fish maintained their equilibrium; as some fish began to move onto the margins of land, those bladders acquired a new utility as reservoirs of oxygen. Biologists say that those bladders were preadapted to become lungs. Evolution can innovate in ways that cannot be prestated and is nonalgorithmic by drafting and recombining existing entities for new purposes–shifting them from their existing function to some adjacent novel function–rather than inventing features from scratch.
—  Stuart A. Kauffman