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Re: Digit Loss

In a message dated 6/8/01 11:48:07 AM EST, twilliams_alpha@hotmail.com writes:

<< Tyrannosaurs had ceased to use their 
 hands for grappling or manipulating prey.  Therefore it doesn't matter how 
 many fingers a tyrannosaur had.  Heck, a few more random mutations and 
 _Tyrannosaurus_ may have had no fingers at all - just a pair of fleshy 
 protuberances attached to each humerus. >>

I don't think digital loss is >anything like< this trivial an occurrence. 
Digital development is not governed by one or two genes that can be turned on 
and off or deleted or suppressed by evolutionary whim; it is governed by 
entire systems of genes. It took some 50 million years of evolution for 
horses to lose their digits, for example, and whole groups of dinosaurs 
shared almost exactly the same fore and hindlimb digit configurations for 
scores of millions of years. Humans today still have the same digital counts 
as amphibians from the Carboniferous Period. Digital counts and phalangeal 
counts persist mightily in the face of immense selection pressure and in 
spite of sometimes drastic limb modifications. It takes an awful lot of 
evolutionary work to make even a single phalanx go away in a lineage.