Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!stanford.edu!rutgers!mbcl!kliman
From: kliman@mbcl.rutgers.edu
Newsgroups: sci.bio
Subject: Re: Coelocanth and evolution:x
Message-ID: <471.284d6041@mbcl.rutgers.edu>
Date: 6 Jun 91 02:05:53 GMT
References: <17580003@hpfcdj.HP.COM> <18@tdatirv.UUCP>
Lines: 30

In article <18@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes:
> In article <17580003@hpfcdj.HP.COM> sharp@hpfcdj.HP.COM (Darrin Sharp) writes:
 
>>	I know that outwardly, the live specimens very closely
>>	resemble the 400 million year old fossils. But how
>>	can this be? Is it common for organisms to not evolve
>>	for 400 million years? How long has it been since sharks
>>	and alligators/turtles/crocodiles evolved? Any other
>>	species that haven't changed in this long? 
 
> *No* species are unchanged for this long.  NGE was wrong.
 
This is clearly a question of semantics.  As far as I know, there is no rule 
that phenotypic change must occur within some specified period of time (e.g., 
400 MY).  That is not to say that such change has not occurred in the 
coelocanth.  However, there are far too many organisms yet to be discovered to
categorically state that phenotypic stasis does not occur.

Genotypic change is a different story - it should occur at whatever the neutral
mutation rate is for every given region of the genome, if all of the rules of 
neutral evolution are obeyed.  So by this definition of "change," even 
organisms with no clear phenotypic change over time are evolving at the 
nucleotide level.  

Still, it seems to me that there must be plenty of cases out there of organisms
resembling, at a morphological level, their far distant ancestors; natural 
selection can favor ancient phenotypes if they remain superior, thereby 
overwhelming the force of mutation.  Why not?

- Rich Kliman