Glen responded:
"Are you saying that DNA has nothing to do with the development
of organisms?"
To which I can immediately reply: On the contrary - it has a very
important role in development.
In my comment, I was concerned about the reductionistic tendency
within science today which has led numerous people to think that
if we can only decode the genome, we will have solved the
problems of development.
Glenn wrote:
I would suggest Scott Gilbert's _Developmental Biology_ He
writes: "Nuclear control of cell morphogenesis and the
interaction of the nucleus and cytoplasm are beautifully
demonstrated by studies of Acetabularia. ...
[text omitted]
This would seem to imply that the nucleus, which is mostly DNA
controls development."
There are numerous questions here, including: What is the nature
of this control? Is it the only control?
Gilbert distances himself from the "solely genetic model of
evolution and development" in a recent paper. I'll quote one
relevant passage:
"Just as the cell is seen to be the unit of structure and
function in the body - not the genes that act through it - so the
morphogenetic field can be seen as a major unit of ontogenetic
and phylogenetic change. In declaring the morphogenetic field
to be a major module of developmental and evolutionary change,
we are, of course, setting it up as an alternative to the solely
genetic model of evolution and development. This, however, is
not to be seen as antagonistic to the principle that genes are
important in evolution or development. This is not in any way
denied. But just as the genes make the cells and the cells form
the body, so the gene products first need to interact to create
morphogenetic fields in order to have their effects. Changes in
these fields then change the ways that animals develop." (p.368).
Gilbert, S.F., Opitz, J.M. and Raff, R.A. 1996, Resynthesizing
evolutionary and developmental biology, Developmental Biology,
173, 357-372.
I'm citing Gilbert because Glenn appealed to him as witness
against the point I made. I consider that Gilbert is more of an
ally than an opponent on this issue.
I'm not endorsing everything quoted here - for example, Gilbert's
constant linking of developmental change with evolutionary
change. I consider this a linkage resulting from presupposition
rather than the results of science. If Gilbert were to address
the distinctions to be made between empirical science and
historical science, he might conclude that there are two
separate, but potentially related, issues to be considered. The
nature of that relationship needs to be carefully probed before
anything meaningful can be said.
Is this an adequate response, Glenn? I did look out a few other
writers who could be quoted to show that morphogenesis
orchestrated by the genome makes no scientific sense. These are
Goodwin (1985), Nijhout (1990) and Harold (1995). If you want
this additional material to further respond to your post, please
let me know.
Best wishes,
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***