Thursday, June 24, 2004

Vestigial Organs Colson's oversimplification in describing junk DNA as meaningless reminds me of another common creationists error: describing vestigial organs as having no function. That is why creationists sometimes write books with titles like Vestigial Organs are Fully Functional.

Scientists often point to vestigial structures such as the eyes of cave-dwelling rodents or the pelvic bones of snakes as being strong evidence for common descent. If snakes evolved from reptiles that had legs, then it makes sense that we would still find pelvic bones in their skeleton. But if they never had legs, it is not clear why they have these bones. But that does not mean the pelvic bones perform no function at all. They do, for example, connect the upper part of their skeleton to their lower part.

The point is not that vestigial organs have no function whatsoever. It is that they no longer perform the function we expect them to perform when we see similar structures in other animals. Or they perform a function out of all proportion to their complexity. For creationists to find some function for a particular vestigial structure and pretend that such structures do not augur well for evolution misses the point.

For more than you ever wanted to know about vesitgial strucutres, have a look at this article by biologist Douglas Theobald. He provides the following useful example:


For example, wings are very complex anatomical structures specifically adapted for powered flight, yet ostriches have flightless wings. The vestigial wings of ostriches may be used for relatively simple functions, such as balance during running and courtship displays—a situation akin to hammering tacks with a computer keyboard. The specific complexity of the ostrich wing indicates a function which it does not perform, and it performs functions incommensurate with its complexity. Ostrich wings are not vestigial because they are useless structures per se, nor are they vestigial simply because they have different functions compared to wings in other birds. Rather, what defines ostrich wings as vestigial is that they are rudimentary wings which are useless as wings.

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At 10:02 PM, Blogger Dr. Andras J. Pellionisz said...

For "Junk DNA" see the hub:

http://www.junkdna.com and its news

http://www.junkdna.com/new_citations.html

For an algorithmic approach, see

http://www.fractogene.com

For PostGenetics, see

http://www.postgenetics.org

Dr. Andras J. Pellionisz

 

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