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Smithsonian Glosses Over the Cambrian Explosion

All photos in this article are by David Coppedge.

Recently we had the opportunity to visit the Smithsonian’s National Museum of Natural History, which exalts Charles Darwin as the uncontested hero of biology. (See, “At the Smithsonian, the Nation’s Museum, It’s All Darwin, All the Time.”) But Mr. Darwin has feet of clay. The Cambrian Explosion, even he realized, threatened his narrative of slow, gradual evolution — a weakness that was exacerbated in the 20th century by fossils from the Burgess Shale. 

Starting in 1909, Charles Doolittle Walcott shipped boxes of Cambrian fossils to the Smithsonian from the newly discovered Burgess Shale in western Canada. The full significance of these fossils was not appreciated until 50 years later, when scientists dusted off the Smithsonian crates and looked at the fossils carefully. Here were vivid impressions of complex animals, they saw, that appeared fully formed without ancestors. Even details of soft parts had been preserved. Stephen Jay Gould also observed that these fossils challenge Darwinian gradualism.

The Smithsonian’s curators today know full well how these discoveries, and subsequent fossils from China, made Darwin’s Doubt worse than Darwin had known. How, then, would they sell the Cambrian Explosion (CE) to the public?

Presentation Strategies

The method could be called interpolation: present the “before” with confidence, present the “after” with confidence, and then deal with the CE as a minor difficulty in between that surely must fit in somehow. Two other strategies were noted: For one, the museum organizes everything into an evolutionary timeline that overwhelms the viewer. 

For another, the curators separated the Cambrian story into two exhibits on opposite sides of the museum. Was this a way to avoid emphasizing to visitors the significance of the CE? 

The most pictorial exhibit is in Fossil Hall, where parents of kids wanting to see dinosaurs would be most likely to pass by.

As for the origin of life, it is merely assumed. “Microbes might have lived on shore by 3.5 billion years ago,” visitors read on an illustrated poster, “relatively soon after the earliest known life appeared” (emphasis added). It appeared. That’s magic talk, not science. And once microbes had appeared, the implication is that they surely must have had plenty of time to tinker with molecules and invent what was coming.

Ediacarans are presented acceptably, with some fossil samples and acknowledgements that “many questions about how they evolved and lived” (but never whether they evolved). The captions do not explicitly say that they were ancestors of the Cambrian animals, but they shown under a bold headline, “The Rise of Animals” (more magic talk). 

Of Charnia, the sign says “they were animals” but without mouths. That is one of four explicit designations of Ediacarans as animals. An adjacent paragraph says, “Typical animal behaviors… had not yet evolved.” The captions avoid mentioning the “Ediacaran explosion” and stretch Ediacaran traits as far as possible to support a vision of evolutionary progress toward true animals.

Muffling the Explosion

Then comes the Cambrian Explosion itself. Suggestive captions repeatedly say that the first animals “evolved” this or that, like hard parts or other features that “allowed them to live in many new and different says.” But “What sparked such innovation?” This key question is answered as if chemistry did it because the new animals needed things. How thoughtful of chemistry! “As calcium became more available in warmer seas, animals used it to make hard parts of calcium carbonate, and, with more animals eating other animals, a protective covering was a big advantage.” Problem solved! Thank you, calcium. 

Then “Life Gets Complicated,” one poster says. How? Cells got more complicated because oxygen was more available. They just did. Simply add oxygen.

Another sign also gives credit to oxygen. Under “Diversity Bursts Forth,” readers find out that “Nearly all of today’s major groups of animals arose” (bold in original) “in this ancient explosion of evolution.” Aha! It was an explosion “of evolution.” 

Note the rhetorical ploys here. They arose. They burst forth. They evolved. Sure, it was an explosion, but it was an explosion of evolution. Moreover, the Cambrian animals had to burst forth; the Earth was welcoming them with open arms, asking “What took you so long?”

Rising oxygen levels, mild temperatures, and higher sea levels made Earth more habitable to ocean life [bold in original]. Some animals began living higher in the water, while others burrowed in the seafloor. Some hunted other animals, and many evolved new defenses. [Emphasis added.]

Once the explosion “of evolution” has been declared, the signs usher readers into a world of trilobites, worms, crawlers, and borers of various kinds, plus “weird wonders” such as Wiwaxia which “may have been a relative of mollusks or segmented worms — or something else entirely.” That pretty much covers the options, doesn’t it? Ah, science.

Never the Twain Shall Meet

Clear across the museum, another exhibit displays a few of the important Burgess Shale fossils, but with less fanfare. They are mounted in glass display cases with captions in small print. Ediacarans such as Dickinsonia and Tribrachidiumthat “made a lasting impression” are shown. 


We learn again that “Life Gets Complicated.” Then comes a big poster. “From Simple Beginnings,” what happened? “The Explosion of Early Life.” Watch this space: 

For more than two billion years, life on Earth changed very little. Then… Wow! [Bold and italics in the original.]

“What happened?” Now that they have your attention, they can give the scientific answer. 

Among other things, oxygen released by simple organisms gradually increased in the atmosphere and ocean. This made possible the blossoming of complex life.

This is rhetoric that would make a Soviet apparatchik proud. Did you catch the escape valve? If you find it hard to believe that oxygen has such powers, remember that it is just one thing “among other things.” Again, that pretty much covers the options, doesn’t it?

True to its Darwin-saturation strategy, the museum connects us rational beings to the lowly worms of the Cambrian. “We Came from Them?” Learning that the basic body plans were established 542-488 million years ago, visitors read,

Your friends, family, and pet turtle may not look much like the creatures here. But we and our fellow animals are heirs of these ancient ocean dwellers.

Not every Cambrian body plan was successful. But those that did succeed set the pattern for every animal that followed — in the water and on land.

Wow indeed.

Now Go Back to Sleep 

In the next display case, “Meet Some of Earth’s Earliest Life Forms,” genuine fossils from the Burgess Shale include Opabinia, Wiwaxia, Hallucigenia, Pikaia (acknowledged to be a chordate), Spriggina, and various trilobites. 

Most viewers are unlikely to pay much attention to these important fossils if they notice them at all. We visited the museum in company with a learned friend, Thomas Woodward (author of Doubts About Darwin and Darwin Strikes Back), who had been eager to see the Walcott fossils. Even we did not notice these until the last few minutes of our visit because we assumed they were all in Fossil Hall. (See the photo at the top of this article.)

In this opposite end of the museum, most of the Burgess fossils are tiny and the captions are in relatively small print. Displays of trilobites on the opposite wall are densely mounted and numbered, requiring visitors to look down at a legend to identify each one. A separate display about Anomalocaris only discusses its features and habitat, not its importance as a complex arthropod that defies Darwinian gradualism. 

One poster explains Walcott’s connection to the museum. After seeing the Burgess Shale in 1909, he “explored the site for the next decade, retrieving more than 65,000 specimens for the Smithsonian collection.” It seems that about 64,980 of them are locked in the basement out of the public eye. 

Another poster shows nine phyla emerging in the Cambrian Explosion. Stephen Meyer’s book Darwin’s Doubt references at least twice that number in the scientific literature. 

An adjacent poster again asks the key question, “What Caused the Explosion of Diversity in the Cambrian Period?” Hey, we already told you. It was oxygen. It was climate change. It was hard parts. It was predation. Why do you keep asking?

The fossil record shows what happened, but can’t tell us conclusively why it happened. Changes in earth’s climateand ocean oxygen levels may have fueled rapid diversification. Another possible cause may have been the interactions among the increasingly complex animals. Competition and predation often spark innovation

Whatever its causes, the Cambrian explosion was unique. Never again have so many dramatically different body plans evolved so quickly. [Emphasis added.]

Got the message? “Whatever” happened, it evolved. No intelligence allowed.

But what was the source of the information required to build hierarchical body plans complete with new cell types, tissue types, organs, brains, and behaviors? That is a question that no amount of oxygen can explain.

In the third and final segment of this photo tour of the National Museum of Natural History, we will see what they do with human evolution.