Re: ILLogical Evolution

Susan B (
Sat, 28 Aug 1999 12:24:09 -0500 (CDT)

Susan wrote:
>>why? I'm extremely curious why you think evolutionists want to conceal the
>>Cambrian. It doesn't really help the creationist case nore does it conflict
>>with evolution. Why do you think it's being concealed?

Cliff Lundberg wrote:
>I think evolutionists in general are not comfortable with the Cambrian
>*explosion*. Of course they admit the existence of "the Cambrian".
>Pure Darwinian gradualism may be passe, but still, anyone who focuses
>on the geologically instantaneous appearance of complex organisms
>comprising all the modern phyla, and who questions the capability of
>known mechanisms for bringing this about, must be prepared for
>accusations of being a closet creationist. We're not going to learn the
>truth when science is thus hindered by Darwinist dogma.

The Cambrian took place over 500 million years. That's not all that
instantaneous in my book. However, the Cambrian is being discussed openly
and in a lot of venues. I think that creationists would dearly love it if
evolutionists would try to "hide" the Cambrian, but it's just not happening.
I have included a long discussion of the Cambrian that originally appeared
in a couple of years ago.

>You mentioned earlier that the evolution/creation controversy was settled
>a century ago. I have to ask, why does it still pique your interest?

it represents a convergence of several interests of mine. I love debate, I
like to be challenged. I love science. I've been a science "buff" for many
years. I collect fossils and mineral samples and read everything about it I
can get my hands on. I think the universe and life are beautiful and
fascinating. Also, I am offended by the arrogance of the religious right
and will frustrate their goals any way I can. Having said that I draw a
certain moral and religious significance from evolution and the history of
life on earth. It neatly supports many things I already believe: that humans
are not outside of nature, but a part of it; that all plants and animals are
related and therefore we are all one family; and that the Earth is our true

>No, the fun is in real science, and in questioning the dogma of smug
>scientists. I ignore the theological stuff on this list; when a long thread
>is running about flood geology etc, I filter those messages out automatically.

so do I frankly. There are a lot of idiots (like Dawkins) who believe that
evolution somehow "proves" atheism. A lot of creationists--like
Stephen--think the same thing. They are both wrong. The history of life just
is what it is. We can draw meaning out of it if we want to (I do, to some
extent) but it doesn't "prove" anything.

>The value here is in the objective critique of evolutionary theory, which one
>doesn't find in textbooks.

probably not. As I said, basically, evolutionary theory is a settled issue.
Science is now busily figuring out the details of how it works.

Article originally posted December 10, 1997 on

>I have heard
>suggested several times that the Cambrian explosion might be an artifact
>of fossil preservation, and I was wondering how much data we have to test
>that hypothesis.

Well one explosion is. There are two aspects to Early Cambrian evolution
which although separate are often confused as one and the same. One is the
rapid diversification of life during the earliest Cambrian, and the other is
the rapid appearance of organisms in the fossil record. Neither event was

The rapid diversification of life in the earliest Cambrian was almost
certainly derived from a pre-existing stem stock of organisms,
representatives of which appear in the Ediacaran fauna. The Ediacaran fauna
appears to contain organisms with a cnidarian-grade of organisation, as well
as the more derived, bilaterally symmetric, triploblasic annelid-grade,
arthropod-grade and probably mollusc-grade. Trace fossils associated with,
but not necessarily formed by, Ediacaran organisms clearly indicate
organisms with a coelomic-grade of organisation (triploblasts). These are
much smaller than the more commonly found fossils and occur in higher
(younger) strata.

All this indicates that Ediacaran organisms appear to have taken two
strategic pathways during the late Neoproterozoic. One group (composed of
representatives of several -grades) opted for passive acquisition of oxygen
via the 'skin' and simple diffusion through the tissues. This allowed them
to grow to very large sizes (c. 1 metre) provided they remained very thin
(oxygen will not diffuse very far through tissues). The other group,
comprised of the triploblasts, opted for oxygen delivery via oxygenated
fluids (from oxygen acquired through the 'skin'). This strategy resulted in
the ability to have a body plan with a circular cross section (the deeper
tissues being supplied via fluids and not simple diffusion) and thus a
coelom. With a coelom, centimetric organisms can be mobile and produce
simple traces, seen as trace fossils in the rocks. Ediacaran trace fossils
are always horizontal - i.e. they do not burrow, probably because 1) there
was plenty of organic matter at or near the surface; 2) burrowing covered up
the 'skin' cutting down the supply of oxygen.

It seems likely that new biochemical pathways were also being explored,
resulting in the production of the metazoan stalwart - collagen. A real
tough customer, providing support and strength with flexibility, and
difficult to break down.

Since all the Ediacaran organisms so far discovered appear to lack any hard
parts it is likely that there were no mobile megascopic predators around (no
hard parts = no teeth, its very difficult to gum something to death!). Thus,
the presence of possible novel biocompounds, the lack of mobile predators
and the lack of burrowers, all combined to provide a taphonomic 'window'
which allowed the preservation of soft-bodied organisms. By the start of the
Cambrian, this system was breaking down.

It is likely that while the big guns were simply getting bigger, the little
guns were getting more complex. The triploblasts were beginning to toy with
differentiation (something the arthropod body plan is particularly good at),
specifically concentration the job of oxygen scavenging to specific body
parts (= gills).

Now, by the very end of the Late Neoproterozoic, two things happened.
Probably a combination of increasing dissolved oxygen levels in the oceans,
but also probably due to the recognition of gills as a smart move. Whatever
the reason(s), organisms began to burrow.

Burrowing is right up there in the list of brilliant tactical manoeuvers. It
confers protection, both from
dirtyfilthystinkingrottencarbonateprecititators (see below) and from storm
activity and the odd vicious undertow. As an added bonus, it allows access
to buried food sources which are denied the third-dimensionally challenged
suckers confined the the top of the sediment. The possession of gills is a
big advantage when burrowing because you can either hang them out in the
current while keeping the rest of the body safely in the burrow, or by
waving them back and forth, you can create a current which brings oxygenated
water into the burrow.

The other thing that happened, was that organisms were toying with the
precipitation of calcium carbonate (calcite). This first appears in the
Latest Neoproterozoic as the calcified inner lining of worm tubes (a trace
fossil called Cloudina). Granted it may well have only been a worm with a
flare for interior design, but it was an important first step. From there it
is only a short peristaltic motion to the mineralization of the tips of such
body parts as legs and jaws. After all it makes burrowing much easier, plus
it has the added bonus of allowing access to all that concentrated protein
wrapped up in collagen! Predation probably took off faster than you can rub
two mineralised jaw elements together.

Thus, with predation mopping soft-bodied organisms off the surface, and
burrowing destroying buried remains, the Ediacaran taphonomic window was
shut. The 'big is beautiful' organisms inevitably lost out. After all, you
may be the biggest redwood in the forest, but you are always going to lose
out to the wimp with a chainsaw!

Once the constraints of oxygen scavenging had been confined to a specific
part of the body, the body plan in general becomes a good deal more plastic
(loose a limb here, fuse some segments there). Thus the seeds of the great
Cambrian Diversification were sowed. Fertilized with a rising sea level to
open up new living space, organisms rapidly, but not instantly, diversified.

The appearance of organisms in the fossil record is a related issue,
resulting from the mineralisation, and hence vastly increased preservation
potential, of organisms. However, this too was not an instantaneous event.

At the start of the Cambrian, we find the first evidence of mineralised
tissues in the form of what appear to be annelid jaw elements and "small
shelly fossils" which are the separate elements of interlocking body armour
worn by annelids, molluscs, halkiirids and probably arthropods. This
meshwork armour was a first attempt and was composed of separate elements
rather than a continuous sheet as it would be later. All this probably came
about because of the segregation of oxygen scavenging to a particular part
of the body, freeing up the rest of the body and enabling THE fashion
accessory of the Early Cambrian to be worn - the calcium carbonate overcoat
- without feat of suffocation. The overcoat provided extra support for
muscles, allowing better movement, and some protection from predators. It
also greatly enhanced the preservation potential of the organism or more
importantly wrt arthropods, moults of the organism (thus one trilobite can
leave behind several images of itself as it grows, with the added bonus of
documenting the growth pattern at the same time - trilobites are cool, they
are the best thing on 24 legs!).

Thus the rapid diversification of life during the Early Cambrian and the
appearance of organisms in the fossil record are related, but separate,
phenomenon. Neither are "sudden" or "instantaneous", but show a sequential,
progressive increase.

Peace is not the absence of conflict--it is the presence of justice.
--Martin Luther King, Jr.
Please visit my website: