Exaptation

By Branden Holmes (Surroundx) on November 28, 2010

Given the fact that plants and animals have evolved so much since the first replicating strands of DNA, different traits have changed roles many times during the course of the history of life on Earth. This is one of the fundamental aspects of evolution. Because natural selection has only the pre-existing body plan to work with, any subsequent change in form must modify the existing format in some way; even the origination of traits from scratch requires an initial duplication of contemporary genes. This change in the role of different traits has been named exaptation by Stephen Jay Gould and Elisabeth Vrba, who introduced the term in a now famous paper entitled, Exaptation-a missing term in the science of form (1982).

They coined the term specifically to replace another term which they felt was misleading: pre-adaptation. However, all orthodox Darwinians who used the term pre-adaptation clearly made it known that they meant in the coincidental sense, and not as a purposeful pre-adaptation to conditions it is known that the population will encounter in the future. Thus, pre-adaptation is not such a bad word that it needs to be replaced. The only confusion that it may cause is that deliberately raised by creationists eager to disprove evolution for purely religious reasons. (paragraph). We have seen that the term is not as ill-suited to the task as Gould had claimed. Evolutionists used the term in a much more limited sense than a change in function of an adaptation. They were simply referring to those adaptations which would also be an adaptation for the same purpose in a very different environment. Thus pre-adaptation does not refer to a shift in function, but rather a shift in environment, and therefore environmental conditions, in which the adaptation still functions in the exact same way as it did in the previous environment. Gould thus erected a straw man, and not even a very good one: “Preadaption seems to imply that the proto-wing, while doing something else in its incipient stages, knew where it was going-predestined for later conversion to flight.” (Stephen Jay Gould, Bully For Brontosaurus, pp. 144n) Coining a term to replace pre-adaptation, which has a totally different meaning than the word that they attempted to replace it with, is clearly bad practice to say the least. However, there is no other elegant single word denoting a shift in the function of an adaptation. Thus it is a welcome addition to the literature, even though ironically its original purpose has itself been exapted to fulfil a new function.

Related articles:
Evolution, exaptation

About Branden Holmes
I am an amateur evolutionist interested in the theoretical side of the subject.

« More articles

The Evolution Forum

An online evolution resource with articles, the latest news, book reviews, databases, links and a forum.

» Home
» Forums
» Articles
» Database
» FAQ
» Links

Cubit owner: Surroundx

» Contact Admin: Surroundx

New Feature! A database of all popular books written on evolution since 1859.

Contact me: brndnholmes[at]gmail.com