Tedd Hadley wrote:
>Cliff Lundberg writes
> in message <4.1.20000830092717.009ca3e0@pop.sfo.com>:
> > <http://www.cab.com/segment/tablecon.html>.
>
> How is your theory distinguished from theories of duplication or
> mutation of homeobox genes as the origin of body plans and
> duplicate segments? It seems to me that if replace your section
> on Parabiosis with a discussion of Hox genes, your theory reads
> pretty mainstream.
I just responded to a post describing my theory as seriously flawed.
Maybe you're both right. But I don't claim anything about hox genes.
I would say there are genes of some kind that control the expression
of a prototype, the prototype being an axial train of segments with
appendicular trains of segments. It's a morphological theory about
physical history. Parabiosis is a morphological phenomenon; you
don't have to know the genetic basis to talk about it; suffice to say
that it's been observed in the present, it could have occurred in
the past.
Should my model ever gain popularity, I'm sure many will say it's
really just old stuff. But the combination of ideas seems new to me:
-- There is a vertebrate archetype; in a limited context where evolution
proceeds through only reduction and distortion of pre-existing parts, it
makes sense to think about what it is that is being reduced and distorted;
call it an archetype. Archetypes are antithetical to open-ended Dawkinsian
evolution.
-- The formation of the prototype (or archetype) is rapid, through parabiotic
macromutation.
-- Complexity in the sense of number of skeletal parts is only increased by
crude parabiotic mutations, not by mutations that cause new individual
buddings of segments in the embryo. The skeleton is formed suddenly,
then it is gradually distorted and reduced in number of parts.
-- The vertebrate skull is formed--in the evolutionary sense--through the
fusion of chains of segments at the anterior of the prototype.
-- Limbs are homologous with the axial skeleton.
Those are the main points that are unique, at least in this combination.
>http://www.mlamutations.com/musings/macroevolution/macroevolution.html
>http://www.bi.bbsrc.ac.uk/WORLD/Sci4Alll/Gaunt/Gaunt2.html
One of these pages starts out mentioning creationism so I assumed
it was a popularization and skipped it. The other postulates primordial
trains of segments, each with its own hox gene(s). I have no idea how that
would work.
--Cliff Lundberg ~ San Francisco ~ 415-648-0208 ~ cliff@cab.com
This archive was generated by hypermail 2b29 : Thu Aug 31 2000 - 01:49:43 EDT