exaptation

:  a trait, feature, or structure of an organism or taxonomic group that takes on a function when none previously existed or that differs from its original function which had been derived by evolution As for exaptations, we need look no further than feathers. It is now argued that feathers were not originally evolved for flight, but emerged in the reptilian ancestors of today's birds, where they served for temperature regulation. — Steven Rose; also :  the condition or circumstance of possessing one or more such traits, features, or structures In fact, it's hard to say just how much of the brain's power is a result of exaptation rather than adaptation. — Tom Siegfried ◆The word exaptation was proposed by Stephen Jay Gould and Elizabeth Vrba in the 1980s as an alternative to preadaptation, which was felt to imply that such traits, features, or structures were destined for a future function. While exaptation has been widely adopted, preadaptation continues to be acceptable in current usage with both terms showing comparable frequency of usage.