From: alc@netcom.com (Chris Stassen)
Newsgroups: talk.origins
Subject: Cambrian explosion (was: "Re: Darwin's Enigma")
Date: 17 Apr 92 04:31:44 GMT
Article-I.D.: netcom.qp1j_cj.alc
Organization: The Lion's Den, San Jose

In article <deKu02Nyce.h00@amdahl.uts.amdahl.com> Jim Loucks writes:
[Mr. Shafto, I think said:]
>> Ah, then it will be easily answered.  A created fossil will start
>> appearing at the moment of creation in the fossil record.

> Similar to the Cambrian explosion? 

I don't really want to jump into this particular sub-thread because
1) I'm already talking with Jim about the same topics elsewhere, and
2) I think Mr. Shafto is doing a fine job and doesn't need any
interference from me.  So, just take this as an rambling, off-
handed comment that you don't need to think very long about or
respond to.

A few of the creationist pamphlets mention the "Cambrian explosion"
as if it were the "creation event" represented in the fossil record.
... "Evolution: Bone of Contention" and "Have You Been Brainwashed?"
to name two.  The latter goes so far as to claim that there are
*no* fossils below Cambrian strata!

So, let's take a short lesson in mainstream geology (unbelievers
can follow along with skepticism; there won't be a quiz afterwards
:-) )...

====================================================================
(I) Fossils below the Cambrian

There are plenty of fossils before the Cambrian.  The Cambrian
begins about 570 Mya (pretend they're depths in feet or something
if you don't like years).  Here is what you can find below it:

3500 Mya - First definitive evidence of life (diverse prokaryotes)
3000 Mya - Stromatolites
1500 Mya - Hints of eukaryotic algae
1000 Mya - Complex eukaryotic algae with apparent organelles
 800 Mya - Flask-shaped micro-fossils
 725 Mya - Cells with crosswalls resembling modern fungi
 650 Mya - 20 genera of various soft-bodied fauna (Ediacarian)

====================================================================
(II) A Very Slow Explosion

The Cambrian "explosion" appears to have occurred over a period of
a few tens of million years.  Here is what shows up where in the
formations at or near the boundary:

1. Ediacarian (670-600 Mya):
	simple trace fossils (trails and burrows)
	a few species of small shell-forming creatures
	coelenterates (phylum containing sea pens, jellyfish, and coral)
	probable annelid worms, possible primitive arthropod
	a few things that are hard to place

2. (600-580 Mya):
	complex trace fossils (apparent arthropod and worm burrows)
	"low diversity" shelly fauna

3. Tommotian Stage (580-560 Mya, encompasses the generally accepted
   Precambrian/Cambrian boundary):
	complex burrows; deep vertical burrows
	archaeocyathids (separate phylum, share some features w/sponges)
	hyolithids (extinct mollusc-like forms)
	monoplacophorans (primitive molluscan forms)
	inarticulate brachiopods
	sponges
	protoconodonts
	possibly gastropods and pogonophorans
	a bunch of shells that don't fit anywhere well

4. Atdabanian Stage (560-540 Mya):
	trilobites

====================================================================
(III) What's missing?

Now to the point I really wanted to make.  Can the Cambrian
explosion (as slow as it appears to be) be counted as a creation
event?  Sylvia Baker says present in the explosion are fossils
"representing every major group of organisms alive today" (_Bone
of Contention_, p. 10).  Apparently, Ms. Baker wants you to think
that the explosion represents the creation of "major groups."

But....

There are no vertebrates involved.  The earliest creature that
can be positively identified as a vertebrate is a jawless fish
that appears in the upper ("late") Cambrian (according to
Carroll, _Vertebrate Paleontology and "the E-word"_  :-)  ).

There are no land plants involved.  Those don't show up until
the Silurian (and even then, they're ones you probably wouldn't
recognize -- modern conifers arrive in the Jurassic and
angiosperms in the Cretaceous).

In other words, you could take a trip to the zoo, see the
flowers, trees, reptiles, mammals, birds, amphibians, fish...
and you wouldn't see *one* creature that shows up in the
"explosion."  (You might notice some algae in the tanks,
but that doesn't count!)

Unless you want "kind" to be above the phylum level (I think I'd
be willing to compromise on "kingdom" :-)  ), you can't point
to the Cambrian explosion as a creation event.
-- 
Chris Stassen						stassen@alc.com
DISCLAIMER:  My employer's account, but not their opinions.
Xref: sparky talk.origins:4207 sci.skeptic:7976 talk.religion.misc:6607