Claim CB926:
Evolutionists invoke preadaptation as an explanation for how some features arose. Preadaptation says that organs and other features evolved before they were needed. But an unneeded feature would never be selected, so the whole concept contradicts the theory of evolution.Response:
- Preadaptation implies that features evolved before they were needed
for the function they eventually served, but not before they were
needed at all. Many organs and features originally evolved for use in
one manner, which incidentally predisposed them for use in another
manner. Once an organ or feature used for one purpose also becomes
usable in a new and more advantageous manner, natural selection will
adapt it for the new use. The following are some potential examples:
- Hard dermal scales in shark skin originally selected for abrasion resistance being predisposed to become teeth
- Feathers on dinosaur/reptile skin originally selected for thermal protection and/or sexual displays being predisposed to become flight feathers
- Lobe fins on fish originally selected for the ability to "walk" through dense underwater vegetation being predisposed to become legs
In each case the organs and features evolved for use in ways that were different from how they eventually ended up being used. At no point did they evolve prior to being useful in some manner, only prior to being useful in the manner they would eventually be used.
Some scientists prefer to use the term "exaption" to explain this phenomenon, specifically to avoid the common misinterpretation of the term "preadaptation" that leads to the above claim. - Some preadaptation comes from adapting to niches that are similar to an ultimate niche. For example, living within talus preadapts ground beetles and other organisms for living in caves.
Further Reading:
Gould, Stephen J., 1977. The problem of perfection, or How can a clam mount a fish on its rear end? In: Ever Since Darwin, New York: W.W. Norton & Co., pp. 103-110. Excerpted at http://www.indiana.edu/~ensiweb/lessons/contriv.pdfcreated 2003-6-13