Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!lll-winken!uunet!tdatirv!sarima
From: sarima@tdatirv.UUCP (Stanley Friesen)
Newsgroups: sci.bio
Subject: Re: Coelocanth and evolution:x
Message-ID: <29@tdatirv.UUCP>
Date: 6 Jun 91 22:15:21 GMT
References: <17580003@hpfcdj.HP.COM> <18@tdatirv.UUCP> <471.284d6041@mbcl.rutgers.edu>
Reply-To: sarima@tdatirv.UUCP (Stanley Friesen)
Organization: Teradata Corp., Irvine
Lines: 36

In article <471.284d6041@mbcl.rutgers.edu> kliman@mbcl.rutgers.edu writes:
>In article <18@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes:
>> *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).

Perhaps so.  But there is no known living *species* that is more than a few
million years old (certainly no more than 10 MY).  And *most* living species
are around one million years old (or even younger).

I would require truly impressive evidence before I would accept a claim
that a *species* was anything like 400 MY old.  Even genera almost never
survive *that* long.  (In fact I believe that the living coelacanth is
in a genus different from all of the extinct forms).  (Hmm, come to think
of it I know of *no* genus that has lasted 400 MY years - I am not even
certain if any *family* of sharks or turtles is that old - though one of
the families of agnathans may be that old).

>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?

Quite true.  But none are so closely identical (even morphologically) as to
be considered to be the same species.  Why this is so is, perhaps,
a problem worth studying, but it is nonetheless true (by observation).

My guess would be that no environment has remained sufficiently unchanged
for more than a few million years for identical phenotypes to continue
to be advantageous.  The least changed forms I know of are probably
crocodiles, but even they are detectably different.
-- 
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uunet!tdatirv!sarima				(Stanley Friesen)