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Should There Be a Time Limit for Cambrian Explosion Excuses?


A hundred and sixty years have passed since Charles Darwin complained that the Cambrian fossil record was his most serious problem, and “at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained.” Nothing has changed, except that now, after two centuries of fossil collecting, it is a worse problem. How much more time to do Darwinians get?

As shown for years in these pages, Darwinians commit two fouls in their scientific papers about the Cambrian explosion. One is to completely ignore the arguments by Darwin skeptics for intelligent design. The second is to hope against hope that a suggestion here or there might “shed light” on the Cambrian radiation. Each time, they issue promissory notes that someday Darwin’s Doubt may no longer “remain inexplicable.” Their critics should say, “Time’s up. You guys lost.”

Another Unhelpful Fossil Deposit

From the Journal of the Geological Society of London, here is another example in the long tradition of making excuses. Kimmig et al. describe “The Spence Shale Lagerstätte: an important window into Cambrian biodiversity.” (In the literature, Lagerstätte refers to fossils of exceptional preservation.) The Spence Shale deposit, indeed, contains exquisitely preserved fossils, shown in beautiful color and detail in the figures. They include many specimens of trilobites and other arthropods, radiodonts like Anomalocaris, mollusks like Wiwaxia, and much more. Located in northern Utah and extending into southern Idaho, the Spence Shale is older than the Burgess Shale. This should allow one to see some evolution, if there were any.

The Spence Shale has been studied for a century, so what’s new in this paper? Here’s the Abstract:

The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätte in northeastern Utah and southeastern Idaho. It is older than the more well-known Wheeler and Marjum Lagerstätten from western Utah, and the Burgess Shale from Canada. The Spence Shale shares several species with these younger deposits, yet it also contains a remarkable number of unique species. Because of its relatively broad geographical distribution, and the variety of palaeoenvironments and taphonomy, the fossil composition and likelihood of recovering weakly skeletonized (or soft-bodied) taxa varies across localities. The Spence Shale is widely acknowledged not only for its soft bodied taxa, but also for its abundant trilobites and hyoliths. Recent discoveries from the Spence Shale include problematic taxa and provide insights about the nature of palaeoenvironmental and taphonomic variation between different localities. [Emphasis added.]

Not much new here. The paper fulfills the first requirement for a Darwinian response to intelligent design: ignore it completely. How about the second requirement, that of issuing promissory notes? Yes, that is obvious in the last paragraph. Note the future tense:

Ultimately, unravelling macroevolutionary patterns in taxa occurring in soft-bodied deposits such as the Spence Shale will probably prove useful for evaluating various hypotheses about the nature and timing of the Cambrian radiation (for discussion of some of these hypotheses, see Lieberman & Cartwright 2011; Daley et al. 2018). In addition, progress recently has been made in understanding the geographical distribution of various fossils in the Spence Shale, but much more information is needed about the stratigraphic and sedimentological context of fossils within and across localities (Box 4). Only then will it be possible to work out the various taphonomic pathways that allowed soft-bodied preservation in this key window of Cambrian life.

Will they ever unravel the macroevolutionary patterns? Will the Spence Shale “prove useful” for evaluating “various hypotheses” about the “nature and timing of the Cambrian radiation”? Will they ever have enough “much more information” to work out the pathways that “allowed” soft-bodied preservation in this “key window of Cambrian life”? It may become “possible” someday over the rainbow. But when the set of “various hypotheses” excludes design by fiat, don’t hold your breath.

Notice that nothing is really new here. The authors found some unique species and problematic taxa, but none of the fossils are transitional forms. They provide no evidence of progress from microbes or Ediacarans to the complex body plans of Cambrian animals. Basically, the same types of animals fit into the same bins as those from other Cambrian deposits. One thing is noteworthy: many of the fossils are well preserved in spite of bioturbation and oxygen.

Intriguingly, the Spence Shale does not record evidence of constant anoxia (Garson et al. 2012; Kloss et al. 2015; Hammersburg et al. 2018). In fact, in the Spence Shale, soft-bodied fossils are also found in association with bioturbated sediments (Garson et al. 2012; Kimmig & Strotz 2017), and geochemical analysis of some intervals indicates oxygenated bottom waters (Kloss et al. 2015).

They are intrigued by this, because it was apparently unexpected. Other intriguing aspects of the Spence Shale are abundant echinoderms. “The diverse echinoderm fauna is unique relative to other Cambrian Lagerstätten of Laurentia,” they say, “as usually sponges are the second most dominant phylum.” This does not help Darwinism. Echinoderms tend to be more complex than sponges. Having diverse types of them makes it worse.

Ad Infinitum, Ad Nauseum

Other recent articles about the Cambrian fossil record continue in the same vein: you might call it the “ignore and hope” strategy. Ignore ID arguments and keep waiting for answers from natural causes.

News from the University of Leeds (see Science Daily) resurrects the oxygen theory. “Extreme fluctuations in atmospheric oxygen levels corresponded with evolutionary surges and extinctions in animal biodiversity during the Cambrian explosion,” this old-news announcement says. The authors ignore ID and hope against hope that repeating the word “evolution” like a mantra will conjure up spirits to conjure up animal body plans out of lazy Ediacarans. The word evolution appears 16 times in the press release, the word oxygen 21 times. Their supporting jargon appears in Nature Geoscience, exploring “Possible links between extreme oxygen perturbations and the Cambrian radiation of animals.” Oxygen is the prima donna in the play, always showing up to offer hope:

Thus, the global extent of well-oxygenated shallow-ocean habitats during the early Palaeozoic, as well as the maximum dissolved oxygen content of surface waters, played a vital role in regulating the emergence and radiation of early animal life.

In Nature Communications, Williams, Mills, and Lenton also pump up the oxygen theory. They describe “A tectonically-driven Ediacaran oxygenation event,” beginning, “The oxygenation of the Earth system was a necessary condition for the rise of complex animal life.” That’s true, but irrelevant. Complex life requires many necessary conditions, all of which are insufficient in themselves. 

It has classically been argued that a minimum oxygen threshold exists for the evolution of animal life, but oxygen requirement clearly depends on the type of animal, including their size, mobility, nervous system (information processing) and ecological habits. Sponges (Porifera) — which are the basal animals — have low pO2 requirements ~0.005–0.04 PAL. Hence their evolution was not limited by any of our predicted pO2 levels, consistent with biomarker evidence that demosponges were present by ~660–640 Ma in the Cryogenian.

It was nice of the early atmosphere not to limit the emergence of sponges. But where did they come from? Surely not from oxygen alone. Where does “information processing” come from? That’s somebody else’s problem, they indicate:

Whilst disentangling the many factors influencing faunal evolution is beyond the realms of this study, we provide the first quantitative prediction of Ediacaran oxygenation that is consistent with geochemical data and with estimated pO2 requirements for the Cambrian explosion.

Want complex body plans? Want information processing, mobility, and nervous systems? We’ll truck in the oxygen, they insinuate; now, go solve the problem.

News from the University of Exeter, where Josh Williams works, explains how blind nature might have trucked in the oxygen. “Plate tectonics may have driven ‘Cambrian Explosion’, study shows.” 

A team of scientists have given a fresh insight into what may have driven the “Cambrian Explosion” — a period of rapid expansion of different forms of animal life that occurred over 500 million years ago.

While a number of theories have been put forward to explain this landmark period, the most credible is that it was fuelled by a significant rise in oxygen levels which allowed a wide variety of animals to thrive.

The new study suggests that such a rise in oxygen levels was the result of extraordinary changes in global plate tectonics.

His co-author Tim Lenton knows about the problem. “One of the great dilemmas originally recognised by Darwin is why complex life, in the form of fossil animals, appeared so abruptly in what is now known as the Cambrian explosion.” Carefully wording his ending dodge, Lenton says, “It is remarkable to think that our oldest animal ancestors — and therefore all of us — may owe our existence, in part, to an unusual episode of plate tectonics over half a billion years ago.”

It is remarkable. So here is a remark. Evolutionary scientists have had 160 years to figure out this dilemma. Give the stage to people who invoke causes that are necessary and sufficient to explain the observations of functional, complex, hierarchically organized animal body plans. ID offers such a cause: intelligence.

Photo credit: Charlie Wollborg, via Flickr (cropped).