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The Economist Admits Cambrian Explosion Is a “Mystery”

Casey Luskin

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A recent video from The Economist takes on the evolution of animals in the Cambrian explosion, conceding something that many Darwin advocates refuse to fully acknowledge: that “biology’s big bang” is a “mystery.” Find it here. Among other important admissions, it says:

  • Narrator: “The cause of this sudden burst of life, which geologists call the Cambrian explosion, remains a mystery.”
  • Andrew Parker, Professor of Life Sciences at the Natural History Museum of London: “The Cambrian explosion was really biology’s big bang. Things went from moving really slowly on the sea floor without any predation to suddenly all the different type of ecologies that we see today. Life literally exploded.”
  • Simon Conway Morris, Professor of Evolutionary Paleobiology at the University of Cambridge: “What triggered the Cambrian explosion? We don’t really know. There are many different possibilities, different hypotheses. And we’ve got to remember that cause and effect are often difficult to disentangle.”

The video then discusses the period prior to the Cambrian called the Ediacaran. But Conway Morris admits that the organisms that lived in this period are not clearly related to the Cambrian animals: “Before the Cambrian we go into what’s called the Ediacaran times. And this is an extraordinary interval where we have the sea floor populated by basically weird creatures. And quite frankly we’re not quite sure if they’re animals or something else entirely.” He explains that these strange organisms “seem to more or less disappear as the Cambrian explosion kicks off.”

This is a nice statement of the problem. The video offers some of the standard weak and inadequate explanations we’ve seen in the past for how the Cambrian explosion occurred. For example, it cites rising oxygen levels as a possible trigger for building larger animals. We have discussed the problems with that theory here, here, here, and here. The video admits, “Evidence to support this theory of higher oxygen levels is scarce” since the ice ages that might have led to larger algae populations which raised oxygen levels “ended 90 million years before the Cambrian.” Indeed, Simon Conway Morris casts doubt on this theory by acknowledging that “oxygen was increasing already, much, much before” the Cambrian period.

The video also notes the hypothesis “that minerals became increasingly available in the oceans due to post-glacial erosion.” These minerals might have spurred the evolution of shells, but the video notes a problem with this hypothesis:

But Cambrian shells were made from a range of materials. This suggests they [were] the result of parallel evolution in different animals lines, not a single innovation. That means something encouraged them to develop on more than one occasion. And shells are costly to make. It’s unlikely mere abundance of minerals would have been enough.

We’ve also discussed problems with this hypothesis here and here.

So how did the Cambrian animals evolve so rapidly? The key to understanding the typical evolutionary position on this question is to appreciate that most evolutionists really aren’t trying to answer that question — at least not in any meaningful way.

ID proponents look at the question and think, “Well, to build all these animals you’re going to need an extraordinary amount of new genetic and epigenetic information, and it’s got to arise very quickly. We must identify some mechanism — evolutionary or otherwise — that can accomplish this feat.”

Evolutionary scientists look at the same question and usually assume that all the information could arise whenever it’s needed. They’re just looking for some kind of trigger to create a selectable need for complex biological systems, and voila, everything happens. They often even assume (as Charles Marshall did)that the information needed to build the Cambrian animals already existed prior to the Cambrian explosion. For example, consider what Shuhai Xiao, a professor of geobiology at Virginia Tech university, says in the video:

The Cambrian explosion happens after a series of events, in my opinion. First you have genetic building blocks to build an animal. You also need oxygen to support metabolism. But that alone is not sufficient. You also need a mechanism to drive the system into a runaway situation. You need to make the system work very fast. And one of the mechanisms to drive the system to a runaway situation is ecological feedback.

Notice that Xiao simply assumes the existence of a full-fledged animal with all of the requisite “genetic building blocks” from the start. Then, all you need is oxygen and the right ecological conditions and all major animal diversity arises. It seems so easy! But they never even attempt to tackle the origin of new biological information.

Simon Conway Morris takes the same approach:

We’re inventing nervous systems. We’re inventing eyes and other sensor systems. We’re learning how to move fast, how to swim effectively. So you have a whole cascade of feedbacks. And it’s really trying to pinpoint “the trigger” versus all the other consequences that flowed from that point.

In other words, explaining the Cambrian explosion entails assuming that a cascade of feedbacks can produce all animal body plans. You just have to look for that one “trigger” that set off the cascade and the rest takes care of itself. But where is the explanation for the origin of all the biological information needed to build these animals? They never touch that question.

An analogy that comes to mind is one we’ve used before — the famous Monty Python skit “How to Do It”:

In the skit, they explain how to cure the diseases of the world, but only in the vaguest and most superficial terms. They never actually give enough information to explain how to “do it” in the real world. The absurdity, of course, is what makes it funny.

The video from The Economist bears a resemblance that’s not as funny. Andrew Parker, for example, says that perhaps “vision was actually the only thing that was required to trigger the Cambrian explosion.” The Monty Python version might go like this: Question: What’s the evolutionary explanation for the origin of all the complex animals that appeared suddenly in the Cambrian explosion? Answer: Well, you see, you start with a full-fledged animal and then it evolved eyes and became very good at catching prey. And then all kinds of other animals had to evolve complicated ways of avoiding being eaten, and then everything evolved!Aside from the fact that this never even touches upon the origin of information, their explanation assumes that there is some evolutionary mechanism capable of generating eyes, and then that there are evolutionary mechanisms capable of generating all animal body plans once eyes evolved. But there’s another major problem: Simon Conway Morris thinks that the eyes of the animals in the Cambrian period couldn’t see things well enough to find them easily, and so eyes couldn’t have been the driver of Cambrian complexity.

There’s one final explanation the video tries out — that the Cambrian explosion was a long, slow process and the early animals were just too small to be recorded in the fossil record: “Perhaps the bilateral ancestors of today’s animals were simply hiding in the shadows of the Ediacaran world until opportunity knocked.”

As Stephen Meyer points out in Darwin’s Doubt, there are small fossils preserved from the Ediacaran period and earlier. So size fails to explain why we don’t see these Precambrian animal ancestors. In any case, the video then says: “Whatever did happen, they took that opportunity, with momentous consequences for the future.”

“Whatever did happen” is right. If you want to understand the origin of information, you’re going to need something capable of generating that information. Returning to the admission at the beginning of the video, from an evolutionary viewpoint that mechanism really is a “mystery.” Allowing for the possibility of intelligent design, however, the answer is evident.

Image credit: Smith609 at English Wikipedia [GFDL, CC-BY-SA-3.0 or CC BY 2.5], via Wikimedia Commons.


Casey Luskin

Associate Director, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.



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