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From: mmt@dciem.UUCP (Martin Taylor)
Newsgroups: net.bio
Subject: Re: limited evolutionary variation
Message-ID: <761@dciem.UUCP>
Date: Tue, 6-Mar-84 17:25:36 EST
Article-I.D.: dciem.761
Posted: Tue Mar  6 17:25:36 1984
Date-Received: Tue, 6-Mar-84 20:21:48 EST
References: <509@uofm-cv.UUCP>
Organization: D.C.I.E.M., Toronto, Canada
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=================
A more interesting question is how those limits are enforced.  Ideally,
there would be a biological mechanism that limits change.  Demonstrating
such a mechanism would be, I think, another excellent way to falsify the
evolutionary theory.
=================
(Limits, in the above == limits on variability of species form).

I don't see the connection.  Surely there exists a perfectly natural
set of limitations on the variability of any species.  Some limits
apply because the organism would die (and many do, before and after birth),
some apply because the organism in its modified form would find no
ecological niche and would be unlikely to reproduce as effectively as
the "mainstream" version of the species.

Isn't the filling of ecological niches what lies behind punctate
equilibrium?  We know from the results of breeding domestic animals
that drastic changes can be developed in a few tens of years when
selection is deliberate.  The genetic mechanisms ALLOW very fast changes
in species form.  But in nature, the empty niches created by the
Lords of Breeding (us) seldom are there for the changed forms to
occupy.  If some disaster occurs and niches open up, then rapidly varying
forms can occupy them.  If there is a general extinction from whatever
cause (sea-level transgression, asteroidal impact, nuclear war), then
the whole niche structure ceases to be self-supporting and the whole
list of major and minor species can be rapidly transformed.

In sum, evolutionary theory seems to demand a biological mechanism
for limiting species variability, rather than being open to falsification
if one were discovered.
-- 

Martin Taylor
{allegra,linus,ihnp4,uw-beaver,floyd,ubc-vision}!utzoo!dciem!mmt