Re: Developmental Evolutionary Biology

Terry M. Gray (grayt@Calvin.EDU)
Mon, 25 Mar 1996 10:36:04 -0400

Art Chadwick wrote:
>Guilbert not only doesn't know the fossil record, he also doesn't contribute
>anything to our understanding by his proposals. To say that the presence of
>developmental pathways common in many organisms can be used as an
>explanation for evolutionary process ignores that the same explanation also
>applies to creation by a wise Creator. What great wisdom does Guilbert's
>proposal supply? All of these mechanisms were already present in the first
>metazoan organisms found as fossils. This still begs the question as to the
>origin or Origin of the mechanisms. Let the question reside there. Clearly
>his proposal supplies no information whatsoever about origin of the
>mechanisms, which is the only information of interest to this group given
>that the presence of the mechanism can be accommodated by either model.

Three questions/comments for you, Art.

First, please explain what you mean by "doesn't know the fossil record".
As far as I can tell Scott Gilbert understands the fossil record just fine.
The following article in this issue of Developmental Biology, while not by
Gilbert, addresses many of the same questions in light of the fossil
evidence "Developmental Evolution of Metazoan Bodyplans: The Fossil
Evidence" by James Valentine, Douglas Erwin and David Jablonski.

Second, do your comments about origin of mechanisms mean that you are
willing to accept the evolutionary explanation beyond that point? So what
if we don't have an explanation for the origin of metazoan complexity (to
be honest, I think that we do have one in rudimentary form--endosymbiosis,
gene duplications followed by mutations that produce novel interactions
which produce new functions that can be be selected for--this is the lesson
we should take from the modular protein story). But most of the issues
addressed in Gilbert's paper addresses the diversification of metazoan
bodyplans and their phylogeny AFTER the origin of the earliest metazoan
organism. If I grant you a special creationist origin of eukaryotic and
metazoan complexity, will you accept evolutionary theory beyond that point?

A long time ago, I asked this group, when it was composed of different
people, at what point common ancestry (evolutionary) arguments broke down.
For example, are all the species of beetles descended from a common
ancestor? How about all insects? How about all arthropods? ... Where do
you draw the line and on what basis do you draw the line?

Third, it seems that for some people biology is the only science where
similar structure, function, mechanism is a sign of an ad hoc common design
special creationist explanation exclusive of some other more unified
explanation. As I've said before, if it weren't for a Biblical
interpretation that demands special creation, the more unified explanation
embodied in evolutionary ideas would be readily accepted. Many of us hear
it shouting at us based on the evidence--of course, we don't share the
Biblical interpretation that demands special creation.

TG

_____________________________________________________________
Terry M. Gray, Ph.D. Department of Chemistry and Biochemistry
Calvin College 3201 Burton SE Grand Rapids, MI 40546
Office: (616) 957-7187 FAX: (616) 957-6501
Email: grayt@calvin.edu http://www.calvin.edu/~grayt