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Explore Evolution claims that the ancestors of the Cambrian phyla could not have been soft-bodied
Summary of problems with claim: This claim is based solely on an quotation from a Discovery Institute Fellow, a toxicologist whose credentials are misrepresented to claim he is a "marine paleobiologist." This claim is a variant of the "gaps in the fossil record" argument, a gap that is being steadily filled by scientists.
Full discussion: This is yet another argument based on a creationist antecedent, "Complex life forms appear suddenly in the Cambrian explosion, with no ancestral fossils." This argument first appeared in Henry Morris's book Scientific Creationism in 1985 (pp 80-81). The authors of Explore Evolution then recast the argument, and cite an interesting source.
This point has been further emphasized by a recent Precambrian fossil find near Chengjiang, China. Scientists there recently discovered incredibly preserved microscopic fossils of sponge embryos. (Sponges are obviously soft-bodied. Their embryos are small and soft-bodied, too—other than their tiny spicules.) Paul Chien, a marine paleobiologist at the University of San Francisco argues that this discovery poses a grave difficulty for the artifact hypothesis. If the Precambrian rocks can preserve microscopic soft-bodied organisms, why don't they contain the ancestors to the Cambrian animals? (footnote 28)
Who is Paul Chien? What are his credentials? What peer-reviewed evidence is cited in footnote 28?
The USF webpage lists Chien's research interests thusly
Prof. Chien is interested in the physiology and ecology of inter-tidal organisms. His research has involved the transport of amino acids and metal ions across cell membranes and the detoxification mechanisms of metal ions.
He is also a "senior fellow" of the Center for Science and Culture, a part of the Discovery Institute, where his credentials are listed somewhat differently.
Paul Chien is a Professor in the Department of Biology at the University of San Francisco and he was elected Chairman of his department twice. He received his Ph.D. in Biology from the University of California at Irvine's Department of Developmental & Cell Biology. He has held such positions as Postdoctoral Fellow in the Department of Environmental Engineering at the California Institute of Technology, Pasadena (CIT); Instructor of Biology at The Chinese University of Hong Kong; and a consultant to both the Kerckhoff Marine Laboratory of the CIT, and the Scanning Electron Microscopy & Micro X-ray Analyst in the Biology Department of Santa Clara University, California. Dr. Chien's work has been published in over fifty technical journals and he has spoken internationally, and on numerous occasions, from Brazil to mainland China-where he has also been involved in cooperative research programs. Dr. Chien edited and translated Phillip Johnson's book Darwin on Trial into Chinese as well as Jonathan Wells' Icons of Evolution.
A search of Web of Science (July 2007) reveals that he is the author of 15 peer-reviewed articles, but none in the area of "marine paleobiology". The most recent article is dated 1998, and is not in any relevant field of biology at all; the title is "Relocation of civilization centers in ancient China: Environmental factors". The most recent biology-related article is from 1995; all of the articles seem to be focused on heavy metal toxicity and antidotes in marine animals, particularly worms (e.g. Uptake, Binding and Clearance of Divalent Cadmium in Gycera dibranchiata (Annelida-Polychaeta); MA Rice and PK Chien; Marine Biology 53 (1): 33-39 1979). He is also apparently a creationist, judging from his statements in a 1997 interview in The Real Issue, which is a publication of the Christian Leadership Ministries, whose Statement of Faith includes the belief in the inerrancy of the Bible.
But when I read Genesis chapter one, the fifth day seems to read very much like the fossil record we see now because it talks about all the creatures teeming in the oceans. Now, to me that sounds like the Cambrian explosion in a very short period of time, [the animals] are all there.
Why, then, is Paul K. Chien described by the authors as a "marine paleobiologist"? He appears to be a toxicologist, whose last peer-reviewed paper appeared in 1998. Those articles in "over fifty technical journals", cited by the Discovery Institute, somehow never made it into the Web of Science. Finally, in the interview cited above, when the interviewer asks him directly if he should be described as a paleontologist, he replies "Not really; that's not my purpose." We can only speculate as to the "purpose" of the authors who do describe him as a "paleobiologist".
What about the references cited in footnote 28? There are two of them. One is a paper (not peer-reviewed) by Chien et al., presented at the North American Paleontological Convention at Berkeley in 2001, entitled "SEM observation of Precambrian sponge embryos from southern China, revealing ultrastructures including yolk granules, secretion granules, cytoskeleton and nuclei". This paper, unsurprisingly, is not indexed in the Web of Science.
The other citation from footnote 28 is Hagadorn, et al., Science, 314:291-294, 2006, "Cellular and subscellular structure of neoproterozoic animal embryos". That paper has already been cited 10 times (Web of Science search performed in July 2007). None of the papers citing Hagadorn et al., cite Chien's 2001 contribution. The Hagadorn paper does not cite Chien either. All of these observations contribute to the perception that Chien's credentials in this area are nil, and that his non-peer-reviewed paper of 2001 has had no impact on this field. His concern about the lack of Precambrian fossils of ancestors to the Cambrian fauna should thus also be viewed with a more critical eye than was used by the authors of this textbook.
But is this question, despite its lack of academic credentials, a valid concern? Why don't we find these missing fossils? More importantly, is a gap in the fossil record a good reason to cast doubt on evolutionary theory and common descent? Probably not. This gap in the fossil record, like all gaps identified by the creationists, is being filled. For some of this more recent information, see the references cited below.
"Darwin's dilemma: the realities of the Cambrian 'explosion'", Morris SC, Philosophical Transactions of the Royal Society B-Biological Sciences 361(1470): 1069-1083 2006
"Fossilized embryos are widespread but the record is temporally and taxonomically biased.", Donoghue PCJ et al. Evolution and Development 8(2):232-238, 2006