On Fri, 19 Apr 96 00:16:06 GMT you wrote:
[continued]
AM>This was the case for some of the "small shellies", which are a
>diverse group of tiny shells found in the time immediately before the
>first appearance of trilobites and for a while after in the Cambrian.
>Paleontologists had no clue what most of them represented. Were they
>complete shells of some sort or pieces of a larger organism with many
>skeletal elements? Some "small shelly" fossils have recently been found
>in early Cambrian (post-trilobite, unfortunately) localities with
>soft-bodied preservation. Some clearly represent the "body armor" of much
>larger metazoan animals that are otherwise soft-bodied. This is more or
>less what one would expect for the earliest skeletal metazoan animals -- a
>skeleton consisting of many separate mineralized elements, making up a
>"scleritome". To say the mystery of the "small shellies" has been solved
>would be an exaggeration, but some of them clearly represent
>partially-skeletonized organisms, and they "coincidentally" are common
>prior to the first trilobites. They are intermediate between being
>entirely soft-bodied and having a complete, strong skeleton.
No doubt, but as you say they are "post-trilobite". But even if they
were pre-trilobite, PC would not rule out a Creator modifying genetic
code in existing "soft-bodied" -> "partially-skeletonized" ->
"skeletonized organisms". The difference is the directed narrow focus
and speed of Intelligent Design (think of the analogy of Artificial
Selection) compared with a random searching "blind watchmaker".
SJ>Yet here we have "the blind watchmaker", which:
>"has no purpose in mind. It has no mind and no mind's eye. It does
>not plan for the future. It has no vision, no foresight, no sight at
>all." (Dawkins R., "The Blind Watchmaker", Penguin: London, 1991,
>p5)
AM>Exactly. Why would trilobites use calcite for lenses when they
>were going to run into all sorts of optical problems the moment the lenses
>thickened or became appreciably more convex to gather more light? If
>they were thin and used in copious light, okay, but what a poor
>foundation. Why not choose an isotropic material where birefringence and
>optical alignment would not be an issue? Bad choice. Poor planning.
>Perhaps what one would expect from *no* planning. They made the best of
>it with schizochroal eyes and their complex corrective optics, but they
>still became extinct.
This is the what Johnson calls then "God wouldn't have done it this
way" argument. He says:
"{In any case, the use of theological arguments-"God wouldn't have
done it this way"-is a very questionable way of proving that Darwinian
evolution was capable of creating complex biological organs."
(Johnson P.E., "Reason in the Balance", InterVarsity Press: Downers
Grove Ill, 1995, p228).
Besides, if the trilobite's eyes worked well, they were not "poor
planning". There may have been a very good (but unknown) reason for
"calcite" to be used. As for becoming "extinct", trilobites were
highly successful, lasting from the Cambrian to the Permian (over 200
million years) being the most dominant form of life for much of that
time. And there is no evidence that their extinction was anything to
do with their calcite optics:
"The trilobites were the dominant invertebrates of the Cambrian, and
they continued to flourish during the Ordovician, but then declined.
They were rare after the Devonian, and the last few survivors finally
died out in the Permian. It is perhaps no mere coincidence that their
decline followed the rise of the giant Ordovician cephalopods and the
hordes of Devonian fishes, both of which could have fed on
trilobites." (Buchsbaum R. "Animals Without Backbones: An
Introduction to the Invertebrates", Volume I, Pelican, 1966 reprint,
p359)
SJ>just happening to find by chance, what Taylor claims is "the one
>material in the universe- namely calcite" (a form of the
>supposedly rare CaCO3)
AM>CaCO3 in the form of calcite is not rare on the surface of the
>Earth. It even forms by non-biological processes.
Agreed. I was referring to the early argument that calcium was rare.
SJ>"which had the required optical properties":
>"One could perhaps accept the idea that a happy accident caused the
>sensitive spots to become more numerous, and that another happy
>accident placed them at the bottom of tubes. It is a little harder to
>accept that by chance the tubes were not parallel, which would have
>been the obvious pattern of repetition, but were slightly divergent.
>But by what conceivable chance could the trilobite have accumulated
>the one material in the universe- namely calcite - which had the
>required optical properties and then imposed on it the one type of
>curved surface which would achieve the required result? There are
>innumerable possible shapes, none of which offer the unique
>advantage of spherical correction, except the one I have
>described." (Taylor G.R., "The Great Evolution Mystery", Abacus:
>London, 1983, p98)
AM>The spherical correction has *nothing* to do with the use of
>calcite. The shape of the lens discovered in the 1700s works as well for
>glass as calcite. I do not know why Taylor thinks calcite is so special.
>All that is needed is relatively high refractive index for an effective
>lens, and an isotropic material could work even better because it could be
>oriented in any direction. There are also many minerals with higher
>indices of refraction (e.g., dolomite, aragonite, magnesite, siderite). I
>am not sure how appropriate these are for biologic systems, with the
>exception of aragonite (another phase of CaCO3), which is used by some
>organisms.
OK. Taylor was an engineer, so he may have had his reasons for
claiming calcite was special. Unfortunately he is dead, so we can't
ask him! :-)
AM>To produce the spherical abberation correction requires little
>more than an appropriately-sized dimple on the inner side of the lens.
>Even an approximation of the exact shape would have a positive effect.
Is there any evidence of a series of "approximation of the exact
shape" in the fossil record?
>AM>This is an exaggeration. Cambrian trilobites had simpler eyes.
>They were only "half clothed" or dressed in "19th century" vintage
>attire. Trilobites of the Cambrian are sophisticated creatures, but lack
>many features found in later trilobites. To a first approximation, what
>Sunderland is saying is correct, but it is an oversimplification.
SJ>See above. While Macbeth may be exaggerating during the heat of a
>debate, it agrees with what Gould and Attenborough say above, even of
>the earliest trilobite eye.
AM>It also agrees with what I said -- that Cambrian trilobites were
>sophisticated creatures, but that the intial ones did not possess the eye
>capabilities explained at length by Attenborough and others.
Agreed. I am happy with that.
[....]
AM>typical invertebrate larvae today). More than what is
>preserved/known as body fossils was present, judging by the burrows
>and trails. There are also some fossils which might be trilobite
>ancestors, but they are not well enough preserved to recognize eye
>details. Most of the soft-bodied preservation so far found in
>Precambrian rocks is just not detailed enough.
SJ>Or they were just not there? :-)
AM>Sure. Always a possibility.
Thanks.
AM>But something was making trilobite-like burrows prior to the first
>appearance of trilobite skeletal fossils. Evolutionary theory predicts
>these were soft-bodied trilobites that had not yet developed mineralized
>skeletons, and it predicts that if Burgess-Shale quality fossil localities
>are found in that interval, soft-bodied trilobites should be amongst the
>fauna. This is discounting the occurrence of potentially trilobite-like
>soft-bodied organisms in the Ediacaran fauna. What does your theory
>predict should be found in this interval?
First, which "evolutionary theory". Gould and his school don't
"predict" it. PC would tend to agree with Gould's punctuationist
model, but for different reasons.
[...]
AM>Zhang Xi-Guang and Clarkson, E.N.K., 1990. The eyes of Lower
>Cambrian eodiscid trilobites. Palaeontology, v.33, part 4,
>p.911-932.
>
>Unfortunately, there is more to eyes than just the lenses, and
>compared to the large number of trilobites known, the eyes of
>relatively few have been examined in detail.
SJ>Maybe knowing more about the trilobite's eye, will only make
>matters worse for evolution?
AM>Entirely possible. Then again, appropriate preservation in the
>Late Precambrian or earliest part of the Cambrian might make things
>"worse" for creationist models that depend upon the Precambrian-Cambrian
>interval representing an "abrupt" appearance with no ancestors for the
>organisms found later [I am not suggesting your theory would experience
>such a problem.]
Agreed. Except, I do not rule out common ancestry. What would
annihilate my PC model would be the discovery of a Pre-Cambrian fossil
bed with the *myriads* of intermediates that must have existed
according to step-by-step blind watchmaker Neo-Darwinist theory:
"Eldredge and Gould certainly would agree that some very important
gaps really are due to imperfections in the fossil record. Very big
gaps, too. For example the Cambrian strata of rocks, vintage about
600 million years, are the oldest ones in which we find most of the
major invertebrate groups. And we find many of them already in an
advanced state of evolution, the very first time they appear. It is
as though they were just planted there, without any evolutionary
history. Needless to say, this appearance of sudden planting has
delighted creationists. Evolutionists of all stripes believe,
however, that this really does represent a very large gap in the
fossil record, a gap that is simply due to the fact that, for some
reason, very few fossils have lasted from periods before about 600
million years ago. One good reason might be that many of these
animals had only soft parts to their bodies: no shells or bones to
fossilize. If you are a creationist you may think that this is
special pleading. My point here is that, when we are talking about
gaps of this magnitude, there is no difference whatever in the
interpretations of 'punctuationists' and 'gradualists'. Both schools
of thought despise so-called scientific creationists equally, and both
agree that the major gaps are real, that they are true imperfections
in the fossil record. Both schools of thought agree that the only
alternative explanation of the sudden appearance of so many complex
animal types in the Cambrian era is divine creation, and both would
reject this alternative." (Dawkins R., "The Blind Watchmaker,
Penguin: London, 1991, p229-230).
Johnson says of mammals, but the same principle applies to the
Pre-Cambrian:
"It isn't merely that grand-scale Darwinism can't be confirmed. The
evidence is positively against the theory. For example, if Darwinism
is true then the bat, monkey, pig, seal, and whale all evolved in
gradual adaptive stages from a primitive rodent-like predecessor.
This hypothetical common ancestor must have been connected to its
diverse descendants by long linking chains of transitional
intermediates* which in turn put out innumerable side branches. The
intermediate links would have to be adaptively superior to their
predecessors, and be in the process of developing the complex
integrated organs required for aquatic life, flight, and so on.
Fossil evidence that anything of the sort happened is thoroughly
missing and in addition it is extremely difficult to imagine how the
hypothetical intermediate steps could have been adaptive. One can't
make problems of this magnitude go away simply by announcing that
there must be gaps in the fossil record." (Johnson P.E. "Evolution
as Dogma: The Establishment of Naturalism", Foundation for Thought
and Ethics, 1990, p35)
AM>In fact, looking back on the history of paleontology, the
>Precambrian-Cambrian interval has become, paradoxically, both more
>"abrupt" and more "gradual". Back in the early 20th century, the first
>appearance of trilobites defined the base of the Cambrian (it is lower
>now), and virtually nothing was known of earlier metazoans. That was a
>truely "abrupt" appearance. Now a succession of organisms are known, even
>if the changes in them are dramatic and poorly understood.
OK. This is a problem for YEC, but it is within the range of
expectations of PC. Darwinism's problem is finding a plausible, 100%
naturalistic mechanism of how these "dramatic" changes ocurred.
SJ>As in the origin of life, the evolutionist's
>problem is "not what we do not know, but what we do know" (Thaxton
>C.B., Bradley W.L. & Olsen R.L., "The Mystery of Life's Origin:
>Reassessing Current Theories, Lewis & Stanley: Dallas TX, 1992,
>p185). Has anyone and idea why or how the trilobite managed to
>stumble on calcite to make an eye,
AM>It was not much of a "stumble". The chemistry of calcite makes it
>one of the simplest minerals to crystallize from seawater. Your question
>is like asking, "How did people stumble on rocks to make a tool?" Calcite
>is often a byproduct of other biological processes, particularly if the
>local ocean chemistry brings calcite nearly to saturation, as is sometimes
>the case.
OK. This seems to answer your "poor design"- "no planning" argument.
An Intelligent Designer would be expected to use the existing physical
laws He had set up. But it still doesn't anwer how a "trilobite"
could "make an eye" by trial and error, and where is the evidence of
the millions if not billions of failed trials and improving eyes.
Your "people" stumbling "on rocks to make a tool" analogy actually
supports Intelligent Design. We know how intelligent chimps and
hominids make tools. In the case of early man we have a record of
improving tool design. We don't have that for blind watchmaker
evolution, even when the conditions for their preservation were good.
SJ>and how it managed by trial and
>error, to develop an already sophisticated eye, up to a degree of
>sophistication that even a modern optical engineer would have
>difficulty emulating?
AM>I could compose a "just so" story -- I have little problem
>imagining how the spherical-abberation-correcting optics could develop,
>and Clarkson briefly discusses how doublets could have developed -- but I
>see little point, because...
Because what? And your "`just so' story" needs to fit the fossil
evidence. That is, if it requires millions of trials, then the fossil
record needs to provide the evidence for those trials.
SJ>And if it was by trial and error, where is the
>fossil evidence of those myriads of failed trials, before it got it
>right?
AM>Much of the evidence to test such a hypothesis stands very little
>chance of preservation. I know, that hoary old chestnut -- poor
>preservation potential -- but go ahead and tell me everything about
>trilobite eyes should commonly be preserved, or that if they were
>soft-bodied at any point, they should be popping out of the rock
>everywhere. Unfortunately the fossil record limits us in terms of the
>questions that can be resolved. The changes in trilobite eyes in the
>Cambrian are particularly problematic because the shedding of the skeleton
>often involved the separate loss of the visual surface. This makes
>finding Cambrian trilobite eyes an exercise in finding needles in a
>haystack. They are known, but are fairly rare. I have several trilobite
>specimens from the Cambrian, but none of them possess eyes. They only
>have an open hole in the skeleton at that point.
So your theory about Pre-Cambrian/Cambrian trilobites acquiring a
calcite eye because it was readily available, and then step-by-step
improving it by trial and error, is untestable?
AM>Practicalities also make it difficult to examine the morphology of
>trilobite eyes through time. There are *alot* of trilobite species, and
>they had a great deal of provincialism. Tracing lineages and cutting up
>specimens for their eyes would take a great deal of work. So far, only a
>limited number of paleontologists who work on trilobites have chosen to
>investigate the optics in any detail. Just the work of Clarkson and
>Levi-Setti covers most of the recent literature. However, there is still
>much more to this issue than what I have described here. If people are
>interested in more detail, I recommend the literature I mentioned
>previously.
OK. Thanks for this helpful and pleasant discussion, Andrew.
Regards.
Steve
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