Comb jellies and sponges and creationists, oh my!

Denyse O’Leary of Post-Darwinist is giddy over some evidence reported in the latest issue of Nature that the lineage leading to living comb jellies may have diverged from common ancestors of later animal life before that of the lineage leading to living sponges. She believes that this is somehow problematic for evolutionary theory since it was previously thought based on their morphology that sponges would have diverged earlier.

O’Leary: Early life researchers had assumed that sponges appeared first because they are so simple. A research team headed by Casey Dunn of Brown University in Rhode Island determined that the much more complex comb jelly came first. Which means that …


Unlike sponges, comb jellies have connective tissues and a nervous system, and so are more complex. Though squishy and tentacled, they are not, however, true jellyfish as they lack the classic bell-shaped body and characteristic stinging cells.The finding was unexpected because evolutionary biologists had thought that less complex animals split off and evolved separately first.


All this shock and awe comes from not taking the Avalon explosion and the Cambrian explosion of life forms seriously for what they can tell us about the real history of life, rather than the Darwinian fantasy.

(In fact, the Smithsonian secretary tried to bury the Cambrian explosion in the vaults in the basement.)

The last sentence here in parentheses (and the article it links to) demands a detailed response of its own, but before I get to that I will address her comments on the recent phylogenomic study.

Part of the problem is that the article she is basing this on is, I think, somewhat misleading in how it presents the story, something not uncommon in media reports regarding evolution, and thus not entirely O’Leary’s fault. The other problem is, and this is typical with antievolutionists, she is not telling the whole story.

The article relates the surprise of the scientists who conducted the study, but doesn’t adequately explain that what was “shocking” was the difference between the expectations they had based on looking at the comparative morphologies of the living representatives from these two lineages and the results they got from their study which was looking at when (relatively speaking) the different lineages diverged genetically in the geologically distant past.

Living comb jellies are more complex that living sponges, but this genetically based study tells us nothing about what the ancestors of living comb jellies looked like when it originally split off the tree, or exactly how long ago this split occurred.

But O’Leary has no use for such subtleties, they don’t score her any rhetorical points. So she passes on the (inadequately explained) surprise part of the story, but leaves out the next part that explains how that even though the findings were a surprise, there are possible evolutionary explanations for this:

The finding was unexpected because evolutionary biologists had thought that less complex animals split off and evolved separately first. Dunn says that two evolutionary scenarios can explain why the comb jellies would actually have been first among animals. The first is that the comb jelly evolved its complexity independent of other animals after branching off to forge its own path.

The second is that the sponge evolved its simpler form from the more complex form. This second possibility underscores the fact that “evolution is not necessarily just a march towards increased complexity,” Dunn said.

Then the article hints at the point I made above:

Though scientists can say which animal branched off first, they can’t date precisely when this early comb jelly diverged away. “Unfortunately, we don’t have fossils of the oldest comb jelly,” Dunn said. “Therefore, there is no way to date the earliest jelly and determine when it diverged.”

Though comb jellies are a common creature in the seas today, these modern specimens likely look very different from their early ancestors.

O’Leary dismisses this last statement with a not particularly relevant story about a fossil crustacean (an ostracod) from the lower Silurian:

O’Leary: Don’t count on that either.

A few years back (2004), I wrote an item for a science teachers’ magazine, “Time Stands Still for Shell Guy?”, detailing an equally remarkable discovery: An early crustacean that had fossilized so quickly in Herefordshire, United Kingdom, that its internal body plan was actually preserved.

And what did they discover? “Researchers are puzzled as to why the ancient creature appears so similar to its modern relatives.”

Sigh. To the extent that researchers simply try to confirm what they think must be true, they will just go on being “puzzled” every few years.

Basically she is using the same argument here that young Earth creationists have for years, the only differences being that YEC usually cite the coelacanths, or some other so called “living fossils“, rather than ostracods. What they are doing is pointing to the exceptions to the pattern of change in the fossil record and claiming that since exceptions exist there is no pattern; that if some groups of animals haven’t changed very much then maybe none have. That this is not the case will be obvious to anyone who bothers to make even a cursory examination of the fossil record.

As for comb jellies (ctenophores) in particular, the University of California Berkeley web site has this to say about comb jellies and their fossil record:

Until fairly recently, no fossil ctenophores were known. Like most pelagic cnidarians, the bodies of ctenophores are made up mostly of water, and the chances of leaving a recognizable fossil are very slim. Two species of fossil ctenophore have now been found in the Late Devonian, in the famous Hunsrückscheifer slates of southern Germany (Stanley and Stürmer, 1983, 1987). Both owe their preservation to rapid precipitation of pyrite in the tissues, and both are quite similar to living ctenophores in the order Cydippida (the “sea gooseberries.”) Other ctenophore-like forms have been found in the Cambrian-age Burgess Shale of the Canadian Rocky Mountains and Chengjiang Formation of Southern China. These forms differ from living ctenophores in several ways, thus obscuring their phylogenetic affinities. (Emphasis mine)

So the earliest (Cambrian) fossil comb jellies, if that is even what they are, may have been different from living species.

Finally on the subject of the phylogenomic study, the article that O’Leary cites is from LiveScience and it is based in turn upon an article from the latest issue of the journal Nature. Now, whenever possible one should always go to the original source, especially when it comes to science reporting. Too often important details are left out or improperly characterized in the translation from peer reviewed journal article to popular level science writing. Had O’Leary done so (and I assume she didn’t) she would have found that the group that did the study made sure to point out that this finding is still provisional:

The placement of ctenophores (comb jellies) as the sister group to all other sampled metazoans is strongly supported in all our analyses. This result, which has not been postulated before, should be viewed as provisional until more data are considered from placozoans and additional sponges. If corroborated by further analyses, it would have major implications for early animal evolution, indicating either that sponges have been greatly simplified or that the complex morphology of ctenophores has arisen independently from that of other metazoans. (Dunn et al. 2008, p. 748, emphasis mine)

If more evidence comes out later that contradicts the findings of this study, I will be surprised if Ms. O’Leary jumps to report it quite as eagerly as she did here.

Now I want to get back to that last sentence in parentheses about a “Smithsonian secretary” who supposedly “tried to bury the Cambrian explosion”.

O’Leary: In fact, the Smithsonian secretary tried to bury the Cambrian explosion in the vaults in the basement.

I wondered what exactly she was getting at, fortunately she provided a link to another article she wrote back in February on a different blog that spells it out. The post is entitled “Critical decisions in science: The Smithsonian secretary vs. the Cambrian explosion“.

In the post O’Leary attempts to sully the name of the late (great) invertebrate paleontologist, Charles Doolittle Walcott. Walcott was at one time the director of the U.S. Geological Survey and later (and until his death) the Secretary of the of the Smithsonian Institution. Among his most notable discoveries was the fossil fauna of the Burgess Shale in the Canadian Rockies (1909).

O’Leary’s defamations are not original to her however, she is passing on the claims of Jewish old Earth creationist physicist Gerald Schroeder.

O’Leary: Walcott found more and more fossils. He shipped over sixty thousand back to the Smithsonian. He had found the equivalent of Noah’s Ark. He found every animal phylum, or – as Schroeder puts it – the “basic anatomies” of all animal life forms today.

Cause for rejoicing? No, because there was a problem. The problem was that the find obviously did not support Darwin’s theory of evolution:

“Eyes and gills, jointed limbs and intestines, sponges and worms and insects and fish, all had appeared simultaneously. There had not been a gradual evolution of simple phyla such as sponges into the more complex phyla of worms and then on to other life forms such as insects. According to these fossils, at the most fundamental level of animal life, the phylum or basic body plan, the dogma of classical Darwinian evolution, that the simple had evolved into the more complex, that invertebrates had evolved into vertebrates over one hundred to two hundred million year was fantasy, not fact. (pages 36-37)”

So the claim here is that “…sponges and worms and insects and fish, all had appeared simultaneously” and are presumably to be found represented in the Burgess shale, which is what is being talked about, and that this is supposedly a problem for evolutionary theory.

Well, there are a couple teeny little problems with Schroeder’s statement.

First, while it is true that there are fossils sometimes referred to as “fish” from the Cambrian, the earliest of these lacked both jaws and paired fins.  For example there is Haikouichthys first described in 1999 from Lower Cambrian rock (530 mya) in China (older that the Burgess Shale), whose closest living relatives would be the jawless scavenging hagfish and parasitic lampreys. Then there are the conodonts, which though jaw-less had tooth-like structures that are found beginning in the Cambrian period. But these were not even understood to be chordates until 1984. Also there has been some evidence found of ostracoderms (jaw-less and armored “fishes”) in the Late Cambrian. However there are no sharks, rays, skates or chimeras (Chondrichthyes – jawed cartilaginous fish), nor are there any goldfish, groupers or guppies (Osteichthyes – jawed bony fish). Representatives of these groups (forget living species) do not appear in the fossil record for another 100 million years or so.

But all these discoveries lay in the future in Walcott’s time. What about Walcott’s fossils from the Burgess Shale; did he uncover any of these supposed evolutionary embarrassments within it’s sediments?

No.

There is a vaguely fish-like chordate known from the Burgess Shale and it was discovered and described by Walcott, a 5cm long flattened worm-like animal, which he named Pikaia gracilens. Here is a reconstruction found on Wikipedia:

Surely this is the smoking gun that Schroeder/O’Leary was talking about, well not quite. You see Walcott did discover and describe Pikaia but he mistook it for some type of Polychaete worm, and thus could hardly have found it to be an evolutionary embarrassment. It wasn’t until 1979 that Pikaia re-described as belonging to the Phylum Chordata.

As for insects, well there simply are no insects found as fossils in the Burgess shale or for that matter in any Cambrian rock. In fact the oldest known insect from the fossil record dates to a little over 400 million years ago, that’s only about 100 million years after the Cambrian explosion. Schroeder ―and O’Leary who quotes him so approvingly―simply do not know what they are talking about.

But this has never stopped an antievolutionist before:

O’Leary: So the reigning theory was probably false. Walcott, remember, was the director of the Smithsonian Institution. And he had just discovered something very inconvenient for the Institution. So what did he do?

Well, he mentioned his spectacular find in Smithsonian Miscellaneous Collections, a publication read by few people. And then he put them in drawers and left them there. They did not receive the attention they deserved for eighty years.

He “mentioned” it in a “publication read by few people”? Really? From this characterization you’d think that he said something about it in maybe one article and that word of the find never really got out for eighty years. Let’s examine this a bit shall we. First some bibliographic information from Walcott (his “mentionings” if you will). From the Talk Origins Archive bibliography on the Burgess Shale we find:

Walcott, C. D., 1911, Middle Cambrian Merostomata. Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 17-40.

—, 1911, Middle Cambrian holothurians and medusae. Cambrian Geology and Paleontology: Smithsonian Miscellaneous Collections, v. 57, p. 41-68.

—, 1911, Middle Cambrian annelids. Cambrian Geology and Paleontology: Smithsonian Miscellaneous Collections, v. 57, p. 109-144.

—, 1912, Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 145-228.

—, 1916, Evidence of primitive life: Annual Report of the Smithsonian Institution for 1915 [published in 1916], p. 235-255.

—, 1918, Appendages of trilobites. Cambrian Geology and Paleontology, IV: Smithsonian Miscellaneous Collections, v. 67, p. 115-216.

—, 1919, Middle Cambrian Algae. Cambrian Geology and Paleontology, IV: Smithsonian Miscellaneous Collections, v. 67, p. 217-260.

—, 1931, Addenda to description of Burgess Shale fossils [with explanatory notes by C.E. Resser]: Smithsonian Miscellaneous Collections, v. 85, p. 1- 46.

That’s 379 pages of “mentioning” right off the bat. Of course the best in this context is this little number:

Walcott, C.D. (1910): Abrupt Appearance of the Cambrian Fauna on the North American Continent; Smithsonian Miscellaneous Collections, v.57, p.1-16. [emphasis mine]

Remember now, Walcott is hiding the “embarrassment” of the Cambrian explosion here (stop laughing).

Unfortunately Walcott wasn’t very successful at keeping the embarrassment of Burgess Shale fauna a secret. Here are a few examples from some older books in my personal library:

Middle Cambrian Burgess Shale Fauna. – In the Selkirk Mountains of British Columbia, famed for scenic grandeur and alpine glaciers, has been found the most interesting locality in the world for Cambrian invertebrates; indeed, it may be said to be one of the most interesting of all time. The bed of Burgess shale that has the fossil community lies on the ridge between Mt. Field and Mt. Wapta, 8000 feet above sea-level. It was discovered in 1910 by Doctor Walcott and he has quarried out of it thousands of specimens described under 70 genera and 130 species. (Schuchert 1931, p.133,  emphasis mine)

The Burgess Shale Fauna. Probably the most significant fossil locality yet known was discovered by C. D. Walcott (Fig. 86) in 1910. It is a bed of slaty black shale of Middle Cambrian date high up on the slope of Mt. Wapta above the town of Field, British Columbia. (Dunbar 1949, pp. 146-147, emphasis mine)

The railroad town of Field, British Columbia, lies between precipitous mountains made up of Cambrian rocks. Northward from Field a trail climbs steeply until it crosses Burgess Pass. Beyond the pass another trail leads to the right, climbing above firs and spruces to beds of blackish mid-Cambrian shale exposed on a barren ridge. The shale was discovered in 1909, after Charles D. Walcott paused to push stone from the trail. When Dr. Walcott last crossed the pass, many years later, he had collected forty thousand fossils from that one small exposure of Burgess shale. Unknown numbers remain in ledges and frost- broken slabs. (Fenton & Fenton 1958, p. 204, emphasis mine)

Nor was it any secret that there was a “Cambrian explosion”, though it wasn’t referred to in that way. Here is one example:

That some great change in the organization of animals took place after Proterozoic time, which ensured their preserval in the rocks, is at once apparent when we compare Cambrian life with that of the foregoing era. The Cambrian strata of North America alone have yielded at least 1200 different kinds of animals, in contrast to the very few known from the Proterozoic. The Proterozoic, moreover, gives us representatives of but three phyla (protozoans, sponges, and worm-like animals), whereas at the outset of the Cambrian five additional phyla ―practically all the important ones― are in evidence (coelenterates, molluscoids, molluscs, echinoderms, and arthropods). Nevertheless, although Cambrian life is primitive, it is not at all as simple structurally as would be expected; in fact, it is far from being the most primitive, since it ranges from simple sponges to complex forms of Crustacea, indicating a long evolution and probable existence of the ancestors of these groups long, long before Cambrian times. (Schuchert 1931, p.130, emphasis mine)

The Cambrian explosion was even discussed in biology textbooks read by school children:

When it is remembered that the Archeozoic and Proterozoic Eras represent together probably at least two-thirds of the time during which conditions on earth were likely to have been suited to the existence of life, the geological record seems meager in the extreme…. THE EARLY PALEOZOIC. The rocks formed during the Lower Paleozoic in North America were in most cases deposited in the shallow water of vast inland seas during a gradual submergence of the land, which ended with fully half the interior of the continent under salt water. For the first time in the geological record fossils are numerous and well preserved. From the dim past life bursts upon the scene in great variety. All the phyla of the Animal Kingdom are represented. (Mavor 1936, pp. 628-629, emphasis mine)

In pre-Cambrian rocks fossils are rare; in Cambrian rocks they are fairly frequent…. By the end of the Cambrian period, all major animal phyla known today (except the chordates) were present…. Diversification was extensive; from Cambrian rocks alone more than a thousand species have been described. (Miller & Leth 1968, pp.349-350, emphasis mine)

Schroeder and O’Leary might wish to quibble with the assumption that Charles Schuchert makes (above) that the Cambrian animals must have had as yet undiscovered ancestors, but they cannot deny that the geologically sudden appearance of most of the animal Phyla in the Cambrian was widely known and discussed, not hidden away as an inconvenient truth (even in public school textbooks).

O’Leary concludes:

O’Leary: Many people have tried to understand and explain why Walcott ignored the significance of his Cambrian fossils, but the most likely reason is that the fossils were not what he had expected to see. He ignored them in order to preserve a belief system.

Which “belief system” was that Denyse? His Presbyterianism?

[Thanks to Don Frack for helping me remember some of the stuff about Walcott's publishing record which we dug up after hearing Schroeder make similar claims at a talk of his we attended a few years back.]

References

Dunbar, Carl O. (1949) Historical Geology

Dunn, Casey W., et al. (2008) “Broad phylogenomic sampling improves resolution of the animal tree of life“, Nature 452:745-749

Fenton, Carol Lane &  Fenton, Mildred Adams (1958) The Fossil Book

Mavor, James W. (1936) General Biology

Miller, William B. & Leth, Carol (Editors)(1968) High School Biology: BSCS Green Version (2nd Edition)

LiveScience Staff (2008) “Shock: First Animal on Earth Was Surprisingly Complex“, LiveScience (website), downloaded on 4-12-2008

Schuchert, Charles (1931) Outlines Of Historical Geology

5 thoughts on “Comb jellies and sponges and creationists, oh my!

  1. Part of the problem is that the article she is basing this on is, I think, somewhat misleading in how it presents the story, something not uncommon in media reports regarding evolution, and thus not entirely O’Leary’s fault.

    Sorry, but if you spend a fair bit of your time commenting on evolutionary biology, as O’Leary does, and you don’t know how to interpret a phylogenetic tree, and she doesn’t, that is entirely your fault. I agree that the article was poorly written though.

  2. Pingback: In principio, Venus perdivit suum cestum mari magno.. « The missing cluster

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