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Re: Definition, please



At 08:34 AM 5/17/97 -0700, T.A. Curtis wrote:
>> Are they exaptions of gastralia?
>
>     I know gastralia.  I don't know exaptions.  Can someone please
>enlighten me?

S.J. Gould and E. Vrba coined the term "exaptation" for the previous concept
of "pre-adaptation".

Aptation: a structure, behavior, etc. fit for a function.

Adaptation: a structure, behavior, etc. fit TOWARDS a function.

Exaptation: a structure, behavior, etc. modified FROM a previous function to
a new function.

For example, the limb bones of tetrapods are adaptations for crawling on
land, and are exapted from the sculling/swimming fin bones of more primitive
vertebrates.

The feathers of early birds were adaptations for flight, but almost
certainly exapted out of some earlier use (thermoregulation? display?).

Hope this helps.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661