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Re: Reevolving bones?



> From:          Adam Yates <zooamy@zoo.latrobe.edu.au>

> I still can't see why you feel that reversals are so unlikely.<snip>, simply 
> because it can be brought about by re-expression of genetic information 
> that was always there but simply not turned on. We know that modern 
> genomes carry un-expressed instructions, for occasionally a mutation will 
> bring them back into use. These atavisms include whales with hind feet, 
> humans with small tails (I even had a friend in high school who claimed 
> his father had tiny holes in his neck that were supposed to be remnants 
> of the pharangeal gill slits that in his case failed to close over - 
> somehow I doubt this example).

Pharyngeal gill slits and thyroglossal duct cysts are well known 
"throwbacks" in humans.  An example of ontogeny recapitulating
phylogeny.  Tails too.  Hirsutism.

However, as far as I know most of these examples are not readily 
inheritable from generation to generation.  Except maybe the tail.  
I'll have to look that up.  Don't expect an answer soon.  I'm 
buried. (Not literally).  So I think it reasonable to expect 
reversals to be rare inheritable events, an exception of the norm.

As always, this is only an opinion, subject to
retraction and recall without notice, and with 
due respect to others opinions.

Thanks,

Michael Teuton MD