Editing Exaptation (section)

==Preadaptation ==
In some circumstances, the "pre-" in preadaptation can be interpreted as applying, for non-teleological reasons, prior to the adaptation itself, creating a meaning for the term that is distinct from exaptation.<ref name="Eshel98">{{Cite journal | author=Eshel, I. Matessi, C. | title=Canalization, genetic assimilation and preadaptation: A quantitative genetic model | journal=Genetics | year=1998 | volume=149 | issue=4 | pages=2119–2133 | doi=10.1093/genetics/149.4.2119 | pmid=9691063 | pmc=1460279 }}</ref><ref name="Masel06">{{cite journal| last=Masel| first=Joanna |author-link=Joanna Masel | title=Cryptic Genetic Variation Is Enriched for Potential Adaptations| journal=Genetics| volume=172| issue=3| pages=1985–1991| date=March 2006| doi=10.1534/genetics.105.051649| pmid=16387877| pmc=1456269}}</ref> For example, future environments (say, hotter or drier ones), may resemble those already encountered by a population at one of its current spatial or temporal margins.<ref name="Eshel98" /> This is not actual foresight, but rather the luck of having adapted to a climate which later becomes more prominent. Cryptic [[genetic variation]] may have the most strongly deleterious [[mutation]]s purged from it, leaving an increased chance of useful adaptations,<ref name="Masel06" /><ref>{{cite journal|author1=Rajon, E. |author2=Masel, J. |author2-link=Joanna Masel | title=Evolution of molecular error rates and the consequences for evolvability| journal=PNAS| year=2011 |volume=108| issue=3| pages=1082–1087 |doi=10.1073/pnas.1012918108 | pmid=21199946| pmc=3024668|bibcode=2011PNAS..108.1082R |doi-access=free }}</ref> but this represents [[Natural selection|selection]] acting on current [[genome]]s with consequences for the future, rather than foresight.

Function may not always come before form: developed structures could change or alter the primary functions they were intended for due to some structural or historical cause.<ref>[http://www.isita-org.com/jass/Contents/2011Vol89/e-pub/21757789.pdf Exaptation in Human Evolution: How to Test Adaptive vs Exaptive Evolutionary Hypotheses]</ref>