a feature that performs a function but that was not produced by natural selection for its current use
a trait that evolved for a different purpose than the current adaptive value of the trait
This was a term intended to cover cases where an organ with one original function got adapted to perform another function (such as the swim-bladders becoming lungs when the first marine creatures became terrestrial). Previously, the term "pre-adaptation" had been used, but this form is objectionable insofar if it suggests some degree of prescience. (WHC: I use it anyway.)
An organism's utilization of a trait or structure for a purpose other than that for which it was originally selected.
an attribute of a species that comes to serve an adaptive role other than that which mediated its establishment.
a trait evolved as an adaptation for one utility is used for a more recent utility (e.g., penguins wings are now used for swimming)
An exaptation is a biological adaptation where the biological function currently performed by the adaptation was not the function performed while the adaptation evolved under earlier pressures of natural selection. Exaptations are common in the history of living things. For example, the gills of aquatic vertebrates function as respiratory organs, while the pharyngeal slits from which gill openings evolved functioned in filter-feeding in ancestral chordates.
