Editing Exaptation (section)

==History and definitions==
[[File:Charles Darwin seated crop.jpg|thumb|upright|Charles Darwin]]
The idea that the function of a trait might shift during its evolutionary history originated with [[Charles Darwin]] ({{harvnb|Darwin|1859}}). For many years the phenomenon was labeled "preadaptation", but since this term suggests [[teleology in biology]], appearing to conflict with [[natural selection]], it has been replaced by the term "exaptation".

The idea had been explored by several scholars{{efn|See Jacob (1977)<ref name=Jacob1977>{{Cite journal |pmid= 860134 |year= 1977 |last1=Jacob |first1=F. |title=Evolution and tinkering |volume=196 |issue=4295 |pages=1161–6 |journal=Science |doi=10.1126/science.860134|bibcode= 1977Sci...196.1161J }}</ref> and Mayr (1982)<ref name=Mayr1982>{{cite book |url=https://books.google.com/books?id=pHThtE2R0UQC |last= Mayr |first=Ernst |year=1982 |title=The Growth of Biological Thought: Diversity, Evolution, and Inheritance|publisher= Harvard University Press|isbn= 978-0-674-36445-5}}</ref> for references.}} when in 1982 [[Stephen Jay Gould]] and [[Elisabeth Vrba]] introduced the term "exaptation". However, this definition had two categories with different implications for the role of adaptation.

<blockquote>
(1) A character, previously shaped by natural selection for a particular function (an adaptation), is coopted for a new use—cooptation.
(2) A character whose origin cannot be ascribed to the direct action of natural selection (a nonaptation), is coopted for a current use—cooptation. (Gould and Vrba 1982, Table 1)
</blockquote>

The definitions are silent as to whether exaptations had been shaped by natural selection after cooption, although Gould and Vrba cite examples (e.g., feathers) of traits shaped after cooption. Note that the selection pressure upon a trait is likely to change if it is (especially, primarily or solely) used for a new purpose, potentially initiating a different evolutionary trajectory.

To avoid these ambiguities, [[David Buss]] et al. suggested the term "co-opted adaptation", which is limited to traits that evolved after cooption.<ref>Buss, David M., Martie G. Haselton, Todd K. Shackelford, et al. (1998) "Adaptations, Exaptations, and Spandrels," ''[[American Psychologist]]'', 53 (May):533&ndash;548. http://www.sscnet.ucla.edu/comm/haselton/webdocs/spandrels.html </ref>  However, the commonly used terms of "exaptation" and "cooption" are ambiguous in this regard.