Here's a quick and dirty response to Paul. Paul, welcome back. You can
subscribe by sending email to majordomo@calvin.edu with "subscribe
evolution" (no quotes) in the body of the message. (Sorry to tempt you so
blatantly =;-)> )
>To the evolution reflector:
>
>In light of the recent commentary on Gilbert et al.
>("Resynthesizing Evolutionary and Developmental Biology,"
>_Developmental Biology_ 173 [February 1996]: 357-372, I'm leaving
>lurker status temporarily, and will keep this short and sweet.
>
>[About me: I'm a Ph.D. candidate at the University of Chicago,
>where my dissertation addresses the relationship between
>development and common descent. Terry Gray, Denis Lamoureux, and
>some of the other old-timers know me from the ancestral form of
>this reflector, when Phil Johnson ran it.]
>
>Gilbert et al. is certainly a step forward for evolutionary
>theory. For starters, it rolls like a tank over the tendentious
>"evolution is change in gene frequency" definition regularly sold
>to the naive on talk.origins by those who should know better.
Glad to see you like it.
>
>But fellas, we've got a long way to go. I wonder if Terry or
>Denis or other enthusiasts for Gilbert et al. 1996 can tell me:
>
>1. If they know of any homeotic mutants -- in mice, Drosophila,
>C. elegans, or wherever -- that don't need a full-coverage Blue
>Cross plan, or, actually, funeral arrangements. More prosaically:
>which known homeotic mutants are good candidates for adaptive
>(viable and fertile) evolutionary change?
Irrelevant! This is the common fallacy that asks of modern "fine-turned"
(canalized) organisms something that was only possible at an earlier time,
before the canalization occurred. The viability of modern homeotic mutants
is just not relevant. Nor is the criticism that they aren't good
candidates for adaptive change. I don't know of anyone who points to
antennapedia as a transitional form to some new species. The point is that
there are genes that regulate bodyplan and that these genes are found in
all metazoans and that small changes to these genes can result in
largescale changes in bodyplan. All these things suggest in a very
powerful way a solution to a longstanding problem--i.e. the pre-Cambrian
explosion and the origin of metazoan bodyplans.
>
>2. If they know of the demonstration of heritable changes to
>cleavage patterns in any metazoan group?
How about the suggestion that cleavage patterns aren't heritable but are
due to laws of form and principles of self-organization? This is the
reason I want to drag Brian Goodwin and Stuart Kauffman into the story.
>
>3. If they've thought 100% seriously about the following passage
>from Gilbert et al.:
>
> The segmentation of Drosophila and the segmentation of
> vertebrates had been a classic example of analogy.
> Yet, here it was seen as being directed by a
> homologous set of genes. This demonstration of
> "homologous" genes for "analogous" processes and
> structures has wreaked havoc with our definition of
> analogy and homology. (p. 364)
>
>For "wreaked havoc," see "stood on its ear," "turned upside down,"
>or, more modestly, "left us scratching our heads about the nature
>of evolutionary change." In brief, macroevolutionary change
>appears not to flow from mutations in nucleic acid outwards to the
>phenotype (via development), because the regulatory genes seem
>boringly similar across phyla.
>
Yep! Small changes in initial conditions can produce large changes in the
final outcome.
You know, the butterfly effect.
>A couple of weeks ago, I saw the galleys for Rudy Raff's new book,
>_The Shape of Life_ (Univ. of Chicago Press, 1996; 520 pp.), due
>out in a couple of months. Raff develops the ideas in Gilbert et
>al. 1996 at great length, and with style and acumen. This is
>evolutionary theory as it ought to be done.
>
Can't wait to see it!
>But don't kid yourselves, guys. Gilbert et al. 1996 belongs on
>Phil Johnson's score card. They confirm what he's been saying,
>and provide NO evidence (see questions 1 and 2 above) that the
>"hang on a sec, we've almost got a theory of macroevolution"
>school is on the right track.
Sorry Paul. As for professional biologists, you are in the minority on
this one.
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
_____________________________________________________________
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