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This Just In — Latest Cambrian Explosion Excuses

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Cambrian explosion

When evolutionists deny design, but admit that nature looks designed, they often wind up attributing the skills of a designer to inanimate matter. This is absurd, but what else is available in their explanatory toolkit?

Here’s an example. A headline by Amanda Doyle at NASA’s Astrobiology Magazine reads, “Microbes set the stage for the first animals.” How is this to be understood? Are animals waiting offstage for their debut? Are microbes arranging the props, clearing pathways, and turning on the lights? Surely she cannot mean that. So how can it be understood without personification? Assuming the prior existence of microbes, perhaps she means that their collective behavior resulted in changes in the balances of gases in the atmosphere, or the pH of seawater, or some other unplanned consequence. Does that help?

Doyle focuses on evidence dating from the Ediacaran Period, just prior to the Cambrian explosion. She weaves her plot around the story of a team from the University of Wisconsin-Madison working in Siberia. Photos show their tools beside unusual limestone rocks containing stromatolites and algal impressions. The photos don’t appear to show any Ediacaran creatures themselves. Indeed, those creatures play no role in her play, so they exit stage right: “The remains of these odd creatures, most of which have no evidence of a circulatory or digestive system, largely vanished from the rock record at the start of the Cambrian Period,” she admits [emphasis added], essentially agreeing with the scientists whom Stephen Meyer quotes in Chapter 4 of Darwin’s Doubt.

According to Doyle’s headline, microbes were recruited as the explanatory heroes in her play. Microbes altered the sediments, leaving records of levels of oxygen and sulfur at the time. The UW team found a stratum where “environmental conditions apparently changed,” going from euxinic (sulfidic) conditions that favored microbe growth to oxygenic conditions that would have favored animals.

The change from euxinic to non-euxinic conditions at the end of the Ediacaran Period allowed the Ediacaran animals to colonise the now more oxidized and habitable ocean, despite an overall oxygen level in the atmosphere and oceans that was far less than today’s.

We need go no further. This is a rehash of the Oxygen Theory we have dealt with over and over (for the latest, see here and here). It makes no sense; oxygen has no power to create animal body plans, nor can it “allow” the animals to create themselves. Mr. Oxygen can cry out, “Bring forth! I allow you to evolve!” all he wants on the stage, but nothing will happen. Can’t someone answer the real argument of Darwin’s Doubt, that the abrupt increase in functional information in the Cambrian animals requires a cause that is capable of producing it? The only such cause we know from uniform experience is intelligence. Oxygen has no such power.

We learn at the end of the article that “The research was supported by the Exobiology and Evolutionary Biology element of the NASA Astrobiology Program.” But Darwin’s Doubt came out four years ago, and Debating Darwin’s Doubt two years later. Is NASA really unaware of the challenge?

Let’s keep looking for an explanation that’s new and different. Here’s one: in Science Advances, the open-access journal of the AAAS, a team of six from four American universities spices up the story of the Cambrian.

Several positive carbon isotope excursions in Lower Paleozoic rocks, including the prominent Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE), are thought to reflect intermittent perturbations in the hydrosphere-biosphere system. Models explaining these secular changes are abundant, but the synchronicity and regional variation of the isotope signals are not well understood. Examination of cores across a paleodepth gradient in the Upper Cambrian central Missouri intrashelf basin (United States) reveals a time-transgressive, facies-dependent nature of the SPICE. Although the SPICE event may be a global signal, the manner in which it is recorded in rocks should and does vary as a function of facies and carbonate platform geometry. We call for a paradigm shift to better constrain facies, stratigraphic, and biostratigraphic architecture and to apply these observations to the variability in magnitude, stratigraphic extent, and timing of the SPICE signal, as well as other biogeochemical perturbations, to elucidate the complex processes driving the ocean-carbonate system.

Further reading doesn’t help. The authors know that “The Early Paleozoic era … encompasses an important time frame in metazoan evolution, including the Cambrian Explosion,” but their research only focuses on correlation, not causation. They mention the same “increase in atmospheric oxygen, possibly associated with an oceanic anoxic/euxinic event” that Amanda Doyle focused on.

Conceptual models have been constructed to explain the causes and effects of these sundry secular changes, including ocean anoxia/euxinia driving trilobite turnover, associated enhancement of organic carbon and pyrite burial forcing changes in atmospheric oxygen levels, and oxygenated coastal waters driving the diversification of plankton and perhaps the resulting Ordovician biodiversification.

The changes could well be consequences, not causes, of the Cambrian explosion. And whether the element is oxygen, sulfur, carbon, or anything else, it doesn’t matter. They’re inert. They’re dumb. None of them has creative powers to design new body plans, cell types, and organs, even if they were to “allow” such things to “emerge” onstage.

We’ll try one more. In Geology, the Ediacaran animal Cloudina is mentioned in a paper by seven researchers from Scotland, Russia, and Namibia. Do they describe a sufficient cause for the Cambrian animals?

The Ediacaran skeletal tubular putative metazoan Cloudina occurs globally in carbonate settings, which both provided lithified substrates and minimized the cost of skeletonization. Habitat and substrate preferences and the relationship of Cloudina to other metazoans have not been fully documented, so we know little as to its ecological demands or community dynamics. In situ Cloudina from the Nama Group, Namibia (ca. 550–541 Ma), formed mutually attached reefs composed of successive assemblages in shallow, high-energy environments, and also communities attached to either stromatolites in storm-influenced deep inner-ramp settings or thin microbial mats in lower-energy habitats. Each assemblage shows statistically distinct tube diameter cohorts, but in sum, Cloudina shows an exponential frequency distribution of diameter size.

Meyer doesn’t mention Cloudina, but it’s not much to look at. Visualize a stack of cups forming a tube. The Virtual Fossil Museum says, “The Cloudinids lived during the late Ediacaran, and became extinct at the base of the Cambrian.” Categorized with the “small shelly fossils” that preceded the explosion, they can’t have contributed to the Cambrian animal body plans, accordingly (see Chapters 13 and 14 in Debating Darwin’s Doubt). We read on, hoping.

In reefs, we document a periodicity of size variation, where mean, minimum, and maximum tube diameters vary together and show a systematic increase toward the top of each assemblage. We conclude that most Nama Group Cloudina represent one ecologically generalist taxon with highly variable size, that size was environmentally mediated, and that Cloudina could respond rapidly to periodic environmental changes. While Nama Group skeletal metazoans coexisted with soft-bodied biota, there was no apparent ecological interaction, as they were segregated into lithified carbonate and non-lithified clastic microbial mat communities, respectively. We infer that ecological flexibility allowed Cloudina to form varied communities that colonized diverse carbonate substrates under low levels of interspecific substrate competition. This is in notable contrast to the earliest Cambrian skeletal epibenthos that formed biodiverse reef communities with specialist niche occupancy.

So that’s it? Tube diameters increased or decreased according to environmental conditions? If they grew articulated legs, eyes and digestive systems, we might be impressed.

Ho-hum. Evolutionists are not responding to Meyer’s challenge. Looks like a forfeit.

Image: Ediacaran creatures, by Ryan Somma [CC BY-SA 2.0], via Wikimedia Commons.