This is, I think, a fair comment.
GM: "I am not sure that animal is more than mere genes. And I am not
sure that Gilbert et al distance themselves from a reductionist
scenario because their next to last sentence. Gene products interact
to create the morphogenic field. Ultimately the morphogens come from
the genes themselves."
This also is fair. I was thinking of commenting on this in my
earlier post - but it was already long enough!
GM: "Is it correct or incorrect that the morphogens ultimately are
coded somewhere in the genome?"
This is, I think, the BIG unanswered question of genetics. Try to
get a proof of the thesis and you will be disappointed. The working
hypothesis of so many geneticists is that all ultimately is coded in
the genome. But it has never been proved. Furthermore, more and
more people are protesting about the working hypothesis. It does not
fit their understanding of the facts. Here are some strong reactions
from a paper by Harold:
"Why do offspring resemble their parents in form and function? The
answer is not known, not even in principle, for the quest reaches
deep into the abiding mysteries of organised complexity." (p.2765)
"Most microbiologists look to the genome to play the architect's
role. From where we now stand, this seems to me to be a rejection of
reason. All we have learned points to the conclusion that several
epigenetic layers intervene between genes and form. Morphogenesis
cannot be orchestrated by the genome, but makes manifest a higher
level of order, corresponding to the cellular scale of size and
order." (p.2771)
"The unstated premise that a cell is at bottom a self-assembling
structure carries reductionism to the point of absurdity" (p.2774)
Source: Harold, F.M. 1995. From morphogenes to morphogenesis.
Microbiology, 141, 2765-2778.
Incidentally, that last quote is one which I am planning to use when
I send a post in on self-organisation. There seems to be a growing
interest in this topic from Christians who do not want to go down the
ID route - and I hope we can explore the subject further than we have
to date.
I wrote:
>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.
Glenn responded:
Consider though what Gilbert is saying about development and
evolution:
"How, then, can one modify one Bauplan to create another
Bauplan? The first way would be to modify the earliest stages of
development. According to von Baer, animals of different species but
of the same genus diverge very late in development. The more
divergent the species are from one another, the earlier one can
distinguish their embryos. Thus, embryos of the snow goose
are indistinguishable from those of the blue goose until the very
last stages. However, snow goose development diverges from chick
embryos a bit earlier, and goose embryos can be distinguished from
lizard embryos at even earlier stages. It appears then, that
mutations that create new Bauplane could do so by altering the
earliest stages of development."
Scott F. Gilbert, Developmental Biology (Sunderland, Mass.: Sinauer
Associates, Inc., 1991),p. 831- 832
GM: "Since the body plan and ultimately the Linnean classification of
an animal is due to the developmental pattern, a change in the
developmental pattern changes the body plan, and thus the
classification."
I accept that morphogenesis is concerned with the origin of a mature
organism, starting from a single cell. And that evolutionary
theories of origins involve organisms going through morphogenesis
during the replication process. But I still think that we ought to
keep the concepts distinct. Morphogenesis belongs to the realm of
empirical science, whereas evolutionary theories are seeking to
unravel a unique pattern of past events. Gilbert's comment about
"mutations that create new Bauplane" goes beyond anything that we
know empirically. The Snow Goose/Blue Goose example is concerned
with a minor kind of speciation, not with a new Bauplan. I'm not
able to supply answers here - but I am seeking to say these thoughts
have a bearing on research agendas and on the way we approach
research findings.
Best wishes,
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***