Exaptation
Pre-Adaptation · Co-Option
A shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another.
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Origin
Coined by paleontologist Stephen Jay Gould and biologist Elisabeth Vrba in a 1982 paper titled “Exaptation — A Missing Term in the Science of Form.” They argued that evolution often repurposes existing structures for new functions — feathers evolved for thermoregulation before being co-opted for flight. The concept challenged the assumption that every trait is a direct product of natural selection for its current role.
Updated February 22, 2026