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From: sarima@tdatirv.UUCP (Stanley Friesen)
Newsgroups: sci.bio
Subject: Re: non-genetic evolution... not
Message-ID: <219@tdatirv.UUCP>
Date: 27 Apr 91 17:24:27 GMT
References: <79788@bu.edu.bu.edu> <47570@ut-emx.uucp> <79798@bu.edu.bu.edu> <1991Apr25.203311.20957@alchemy.chem.utoronto.ca>
Reply-To: sarima@tdatirv.UUCP (Stanley Friesen)
Organization: Teradata Corp., Irvine
Lines: 43

In article <1991Apr25.203311.20957@alchemy.chem.utoronto.ca> mroussel@alchemy.chem.utoronto.ca (Marc Roussel) writes:
>...  It seems to
>me that this qualifies as evolution in a less restricted sense than the
>current dogma allows: a species can be said to have evolved a trait if
>this trait is transmissible from generation to generation and stable
>against reasonable environmental perturbations.  (I will let someone
>else define "reasonable" and "external environment", if any of this
>makes sense.

I think it makes a certain amount of sense.  The main reason for the current
emphasis on the genetic component of change is because that is the one type
of change we *know* is transmissible, as opposed to externally imposed.

To Darwin, at least, the main point of evolution was the selection of
heritable (== transmissible) changes (or variation).

>Surely in the case of the wasps and their symbiotic partners, the
>symbionts form one system and thus are not part of the external
>environment.)  This definition of course excludes (quite rightly) trivial
>cases like the "better nutrition = taller humans" effect which Chris mentioned.

An interesting sidelight her is that there *is* a genetic component in this
system.  The *symbiotic* *microbe* does in contain genes coding for lack of
males in the wasp.  (Shades of night - a gene in a microbe coding for a
feature in its host?!?!).  And this gene is certainly beneficial to the
microbe, and is thus selected for.  What is happening here appears to be a
breakdown of the normal seperation between organisms.

It is certainly admitted that at some point a former symbiont becomes a
part of its host, at which point the distinction between 'genetic' and
'non-genetic' inheritance ceases to be meaningful.  In the case of
mitochondria and chloroplasts most of the genetic control has actually
been transfered to the eukaryotic host (which is the other direction than
the wasp example).  Nonetheless there are a *few* traits that are still
coded for in the organelle itself, leading to strange forms of 'cytoplasmic'
inheritence.  (Look at the 'Eve' studies in anthropoology).


So, it gets quite interesting, the borders of things are actually quite
fuzzy.  Which is very normal in biology.
-- 
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uunet!tdatirv!sarima				(Stanley Friesen)