Cliff:
Thanks for the reply. The references on the late Precambrian
phosphaticized fossil embryos of modern phyla are Science, 6 Feb. 1998,
and Nature, 5 Feb. 1998.
>
>As to your web site, I would say it is a diligent and competent effort,
>but really the same old stuff. I think evolutionary science would be
>better off if it were acknowledged that the Cambrian Boom is quite a
>mystery and that conventional theory does not explain it satisfactorily.
>Your implication (elsewhere in your text) that conventional gradual
>evolution underlies it, but that the lack of hard parts precludes our
>observing the process, is a speculation without support. The fishes
>that popped (apparently) into existence do have hard parts, and we do
>have pre-Cambrian fossils of soft-bodied organisms.
>
I agree--it is the same old stuff, but it's same old stuff that has been
convincing to thousands of scientists for over a century. The Cambrian
Explosion is a mystery in some respects, certainly, but not in the way
that creationists imply. I don't believe and didn't claim that
conventional gradual evolution underlies it (it was probably fast and
punctuational evolution following a mass extinction), but I do claim that
the disjunct adaptation of hard body parts is responsible for the
separate and apparently sudden appearance of highly-differentiated
metazoans during a geologically-short period of time in the Cambrian.
This is hardly speculation: the Burgess Shale fauna shows a remarkable
number of highly-diverse metazoans that had not yet evolved the
calcareous exoskeleton adaptation; most taxa probably were not calcified.
The Precambrian Vendian/Ediacaran Fauna is probably not ancestral to the
modern phyla that appeared in the Cambrian. In fact, it was probably the
Vendian fauna that underwent the extinction that made it possible for the
modern phyla to radiate.
Steve