Re: EvolutionVsDevelopment
Mon, 27 Jan 1997 22:29:23 -0500 (EST)

Glenn wrote on Sat, Jan 25,

"Some sequences do not allow a living being to survive. These "bad"
sequences are removed by natural selection. But as long as there is a path
through the sequence space from one sequence to another in which all
sequences allow a living being to exist and reproduce, then mutation can move
from one species to another."

Comment: Does natural selection do nothing more than remove "bad"
sequences? I don't think most evolutionary authors would be satisfied with
that, including Darwin, Mayr, Dawkins, Dennett, among others. As I
understand Darwinian theory, natural selection is the critical process that
drives evolution and adapts organisms to their niches. You now seem to be
substituing concepts from information theory, which I obviously do not
understand, such as, "pathway", "sequence space" "billions of dimensions",
"mathematical space". Natural selection no longer plays a role, as far as I
can see. You say, "But as long as there is a path through the
sequence space from one sequence to another in which all sequences allow a
living being to exist and reproduce, then mutation can move from one species
to another....If there is a path into that point, *it can be found by random
mutation, given enough time*." Are you saying that random mutation can do it
by itself, without the shaping role of natural selection? This lack of a
role for natural selection (except to remove "bad" sequences) leaves
information theory quite unsatisfactory as far as I'm concerned; and I see
little empirical confirmation of the computer simulation.

You wrote, "The nature of a lot of mutation is that it changes a whole lot
of things all at once. To assume that mutation produces small change and
another mutation produces another small change is an outdated view of how
mutation and development work." You go on to quote Gould, "Genetic systems
are arranged hierarchically; controllers and master switches often activate
large blocks of genes. Small changes in the timing of action for these
controllers often translates into major and discontinuous alterations in
external form."

Comment: How do these concepts apply to the transition between fins and
legs. What are these "large blocks of genes" that Gould posits? Where do
they come from? Let me suggest that they may constitute *developmental
programs* that I believe lie unexpressed in the phyletic germ line until
activated by controllers and master switches. Perhaps they are the
"developmental patterns" that Vermeij suggested were the products of the
Precambrian putative formation of phyla, that I referred to in a previous

On the other hand some times a single gene does it all. A single gene--not
several--is enough to spark the formation of a major structure like wings in
Drosophila according to Carroll in Nature, July 11, 1996. The gene called
*vestigal* caused wings to grow in tissue that doesn't normally form wings,
such as eyes, heads, antennae, or legs. So genes apparently work in various
ways. Incidentally, such a single gene as *vestigal* which does so much
makes it at least possible to think that the original genome of a lineage
could hold a great deal of structural genetic material in suppressed form for
future phyletic development.

You wrote, "As I noted, 3 mutations perform most of the morphological change
between two species of monkeyflowers."

Comment: In my humble opinion, your example is not relevant to how fins
were transformed into vertebrate legs. The major innovation represented by
the transition from aquatic to terrestrial life is not explained by
microevolutionary change of one species to another. The transition from
aquatic to terretrial life happened far upstream when major changes were
being made. The change from one species to another pales in comparison.

I wrote in my last post that "Development also works on a sliding scale. It
starts out high, and ends low. NS starts low and ends high." To which you
replied, " There is none of theis high and low business. None of this higher
and lower animals as far as I can see."

Comment: I was not referring to higher and lower animals. Early in the
Phanerozoic, far upstream in phyletic development, the developmental process
starts out high, i.e., the percentage of morphological change that can be
ascribed to it is high. Toward the end of the Phanerozoic it is low. NS is
the reciprocal. It starts out low in producing major innovations at the
beginning of the Phanerozoic and ends high toward the end of it .

I wrote in my last post that there are questions that I find difficult to
answer, and gave examples. You answered, "Unfortunately, a good theory
needs to be able to answer questions like this. If you are wanting to replace
evolution, you also need to be able to have a theory which makes predictions
which evolution does not make and which then turn out to be true. I would
encourage you to develop solutions."

Comment: I am aware of all this. I am not trying to replace evolution. I
am trying to reposition it. Microevolution is a well documented process that
is occurring at the present time. It became a dominant process in the latter
half of the Phanerozoic, after the developmental programs have been activated
and are in place, and as the developmental process begins to run out of
steam. The acceleration of speciation in the Cenozoic suggests that natural
selection, of which species are a by-product, has gradually become a dominant
biological process. The paucity of species early in the Phanerozoic gives
credence to the concept that development rather than NS was the dominant
process early on.

But I also remind you that Darwin was unable to answer all the questions that
could be put to his theory. The question about the source of variation that
he made a cornerstone of his theory is an obvious example. Thomas Kuhn also
said that a given theory is not necessarily able to answer all the questions
that can be addressed to it. So because developmental theory is not able to
answer all the questions you raise at this time doesn't mean that it is ipso
facto invalid. I agree, however that much more needs to be done, and I
appreciate the questions you raised.

On the other hand our exchange of notes has not permitted me to provide other
evidence for the developmental framework. And this is not the best format
for presenting it. As I said earlier I am in the process of preparing a
summary of the theory, which when I complete I will be glad to share with
you, if you wish, for your comments and questions.

So much for the time being.


You asked, "So where does that new phylum of cycliophora come from?" At
this point nobody knows. I