Several questions on evolution, and mutation (rate)

Doug Yanega dyanega at denr1.igis.uiuc.edu
Tue Sep 3 14:23:55 EST 1996


In article <96Sep2.121604edt.860 at neuron.ai.toronto.edu>,
radford at cs.toronto.edu (Radford Neal) wrote:

> In article <dyanega-0109962027360001 at catalpa.inhs.uiuc.edu>,
> Doug Yanega <dyanega at denr1.igis.uiuc.edu> wrote:
> 
> >I am NOT redefining evolution, I am instructing the non-biologists here
> >what the accepted biological definition has been for much of this century.
> 
> I think you are quite wrong in this regard.  First because, as I
> pointed out previously, your definition of evolution as "changes in
> frequencies of alleles" fails to capture the reason why evolution is
> an important subject.  Second, because it is a pathetically inadequate
> definition even if one were aiming at a technical characterization for
> use when the conventional views on which it is based are not in dispute.

There is no requirement that the definition of evolution "capture the
reason" why it is important. As for whether it is "inadequate", that is
your own opinion, not shared by the biological community. Like I said, if
you don't like the accepted definition, then next time you engage in a
debate, supply YOUR definition so the evolutionary biologists will know
what YOU mean.

> Even the most casual acquaintance with the variety of organisms on
> Earth should reveal to you that they differ in more than the
> frequencies of alleles.  The concept of an "allele" applies only when
> the set of genes is regarded as fixed, which is clearly not the case
> when considering organisms that differ wildly in the number, length,
> and organisation of their chromosomes. 

This has nothing to do with the concept of an allele.

> You might also like to consider
> whether your definition of evolution is adequate to describe the
> origin of the eukaryotes via endosymbiosis - or for that matter, of
> lichens.

It is perfectly adequate as long as you are willing to recognize that
lichens are assemblages of two different species, each of which is
following its own evolutionary path. A lichen is not a single species,
therefore a lichen cannot evolve except in a figurative sense. The fungal
symbiote can evolve, as can the algal symbiote, and they can evolve
independently. Figs and fig wasps evolve independently, too, it's just
that laymen are less likely to make a conceptual blunder there as they
might with things like lichens. 
   As for endosymbiosis, your perspective will depend on when you consider
the boundary between two symbiotic species and one composite species to be
crossed. Heck, there are people who consider the evolution of the
mitochondrial/chloroplast genome separately from the evolution of the
nuclear genome, so one can take it to an even finer level by partitioning
the genetic composition of a species. That's one way around the ambiguity,
yet it still uses essentially the same definition of evolution; it just
splits things up into alleles borne in the nucleus versus alleles borne in
the organelles. Also, when you talk of the *origin* of eukaryotes, you're
talking about speciation, rather than evolution.

> If you're going to ignore all this, 

It doesn't ignore all this, it is quite accomodating for your preceding
"exceptions".

>however, why stop at frequencies
> of alleles?  Why not go all the way, and declare that evolution is
> really about changes to an organism's DNA - even if the changes are in
> a non-coding region, or if the change is from one codon to another
> that is synonymous.  That'll stop those ignorant critics cold - easily
> demonstrated *proof* that evolution occurs all the time! 

Actually, I think many molecular systematists would agree with you
entirely. They often reconstruct phylogenies of taxa based on non-coding
regions of the genome, so clearly non-coding regions *reflect* the
evolutionary process, at the very least. You are confusing natural
selection with evolution again. Even Darwin did not make that mistake.

> Sure, they
> may still question whether eyes or hands can really evolve by this
> mechanism, but with this definition, it is easy to see that evolution
> really has nothing to do with things like eyes and hands. 

Not unless you like to get sloppy about your definition. Evolution is
something that is a population- and species-level property. An individual
organism cannot evolve, only a group of them among which there is gene
flow. An organ or structure cannot "evolve," except in the layman's sense
of the term. That usage is sloppy, and you must STILL recognize the
underlying definition as appropriate - eyes and hands will change in an
evolutionary sense only when the genes controlling their form and function
change. No matter how you slice it, evolution is a function of population
genetics.

> The fools
> just don't know the up-to-date definition, being stuck in the rut of
> thinking of evolution in the same way that Darwin did.

I think Darwin had a much clearer idea than you do, given your confusion
between selection, evolution, and speciation. At times you seem to be
conceptualizing things as if these three terms are synonymous. They are
not. Selection is not required for evolution to occur, though it is one
type of evolutionary process. Evolution can occur without leading to
speciation, but speciation cannot occur without evolution (there is no way
for something to be a new species without possessing alleles different
from its ancestor's). Now perhaps you can understand why it is absolutely
*essential* that there be a rigorous standard definition; it helps one
avoid confusion about the different levels of process.

> Winning arguments this way clearly has certain advantages - in the words
> of Bertrand Russell, "they are the advantages of theft over honest toil".

Give me a break. Why not try some "honest toil" over a scientific text on
evolutionary biology for a while and THEN come back and argue.

Doug Yanega     (dyanega at mail.inhs.uiuc.edu)
Illinois Natural History Survey, 607 E. Peabody Dr. 
Champaign, IL 61820  USA  (217) 244-6817 fax:(217) 333-4949
affiliate, University of Illinois Dept. of Entomology
  http://www.inhs.uiuc.edu:80/~dyanega/my_home.html
"There are some enterprises in which a careful disorderliness is
    the true method" - Herman Melville, Moby Dick



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