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From: colby@bu-bio.bu.edu (Chris Colby)
Newsgroups: sci.bio
Subject: non-genetic evolution... not
Message-ID: <79798@bu.edu.bu.edu>
Date: 21 Apr 91 20:05:08 GMT
References: <18637@csli.Stanford.EDU> <79788@bu.edu.bu.edu> <47570@ut-emx.uucp>
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Reply-To: colby@bu-bio.UUCP (Chris Colby)
Organization: Biology Dept., Bost
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In article <47570@ut-emx.uucp> bill@ut-emx.uucp (Bill Jefferys) writes:
>In article <79788@bu.edu.bu.edu> colby@bu-bio.UUCP (Chris Colby) writes:
>#In article <18637@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU (Chris Phoenix) writes:

>#>Is this totally off base, or is non-genetic evolution a possibility?

>#	It's totally off base ;-) Non-genetic evolution is an
>#oxymoron.

>Actually, Chris P. is not so far off as one might think.
>_The Economist_ had a story this week (in the science section)
>about a certain species of wasp that reproduced parthenogenetically;
>all of the offspring are female. Yet, if the wasps are fed 
>antibiotics, they will produce males and females in 50%
>ratio. Why? It appears that a bacterium has co-evolved
>with the wasp. It is transmitted via the eggs (see Chris
>P's speculation above!!!), and has evolved the ability to
>supress the production of male offspring. Presumably this
>is because it provides an advantage to the bacterium!

	Yes, I read this when it came out in the literature.
There are also wasp species that can interbreed when fed
antibiotics, but not when they have the internal bacteria
present. Interesting stuff.

>Yet the wasp retains the ability to produce males, so it
>is the _conditions_ under which the embryo develops
>that determine the sex. A non-genetic "evolution" that
>"breeds true" as long as the bacterium is present.

	You are confusing the process of evolution with simple
change. If the gene pool of the wasps did not change (ie there
are still the same frequency of male and female determining 
genes), then the population did not evolve. This is true even
if there are more females than males compared to some time in
the past. Let me give an example to illustrate my point.

	Humans have been growing larger and heavier in recent
historical times. But this is not an evolutionary change; it
is a result of better nutrition and medicine. If the environment
returned to old conditions, humans would be shorter and thinner.
In other words the genes have stayed the same (roughly), but the mani-
festation of them has changed. The same is true in the wasps;
the gene pool has not changed (or at least we'll assume it
hasn't for the sake of argument) but the expression of the
genes has changed due to a change in environment (presence of an
internal endosymbiont). They have changed, but they haven't
evolved.

	Remember that evolution is _defined_ as a change in the
gene pool; therefore non-genetic evolution is by definition non-
sensical. Populations phenotypes (expression of genes) can change
without the gene pool changing. This can often be very interesting
(as in the wasp case), but it is not evolution.

>Bill Jefferys

Chris Colby
email: colby@bu-bio.bu.edu