The Mystery of the Cambrian “Explosion”

ONE of the standard items of propaganda that creationists like to sling around in their ceaseless crusade against reason is that science has no explanation for the so-called Cambrian Explosion. A typical example is this, by Casey Luskin: BioEssays Article Admits “Materialistic Basis of the Cambrian Explosion” is “Elusive”. Here’s another by the same author: Strengths and Weaknesses in David Hillis’s Arguments about the Cambrian Explosion.

The general idea they hope to leave you with is that back in the long-ago Cambrian their supernatural Designer visited earth and performed his mysterious work to magically create a variety of “kinds” which couldn’t possibly have been the result of evolution. That’s their “scientific theory.” But was the “explosion” so incredible that it requires a supernatural explanation?

The Cambrian lasted at least 50 million years. Consider how long that is for purposes of evolutionary change. Let’s say that our own splendid species has been around for roughly 1 million years, and a human generation is 20 years. Okay then:

100 years = 5 generations
1,000 years = 50 generations
10,000 years = 500 generations
100,000 years = 5,000 generations
1 million years = 50,000 generations

That’s a lot of generations during the brief period that we’ve been here. In that short time (geologically speaking), a bewildering variety of dogs have descended from wolves. Galapagos finches change beak sizes within the time frame of human observation (see: Evolution Here, Now, Everywhere). A new breed of tame foxes can appear in only two human generations (see: Domesticated Silver Fox). Peppered moths have changed from white to black and back to white again, all within recent industrial history (see: The Peppered Moth is Turning White Again). What evolutionary changes were possible for us in a span of 50,000 human generations? We’ve found fossils of closely-related species, and although only one human species exists today, we exhibit considerable variation — from pygmies to Danes.

The length of time required for the Cambrian “explosion” was 50 times longer than that, so in human terms it would have been 2.5 million generations. Of course, we’re large animals, and human generations require a long time. Bacteria, in contrast, breed a couple of times each hour. If the typical creature living during the Cambrian required a full year between generations, they had time for 50 million generations. In all likelihood, reproduction in the Cambrian for the simple creatures then alive took much less than a day, possibly only an hour, so there were literally billions of generations during that “explosion.”

Creationists are fond of claiming that Noah’s Ark had plenty of room to contain at least one breeding pair of all land animals on earth. Fine. If they’re that imaginative regarding the capacity of physical space, then they can be similarly generous regarding time. If so, they’ll surely agree that the Cambrian had plenty of time for a whole lot of “micro” evolution to occur; and in a span lasting 50 million years, the cumulative effect of billions of generations was sufficient for all that “micro” evolution to become “macro” evolution.

Will the creationists make that admission? No, because with creationism, integrity is the first casualty. As a fictional character famously said:

“Once you give up integrity, the rest is a piece of cake.”
— J.R. Ewing

However, Arizona State University geologist L. Paul Knauth has been doing a bit of work on the Cambrian. At that university’s website we read this news item: Explosive growth of life on Earth fueled by early greening of planet. Here are a few excerpts, with some bold font added by us for emphasis:

Earth’s 4.5-billion-year history is filled with several turning points when temperatures changed dramatically, asteroids bombarded the planet and life forms came and disappeared. But one of the biggest moments in Earth’s lifetime is the Cambrian explosion of life, roughly 540 million years ago, when complex, multi-cellular life burst out all over the planet.

While scientists can pinpoint this pivotal period as leading to life as we know it today, it is not completely understood what caused the Cambrian explosion of life. Now, researchers led by Arizona State University geologist L. Paul Knauth believe they have found the trigger for the Cambrian explosion.

As you can see, dear reader, Dr. Knauth — here’s his page at the university’s website — is going beyond a mere description of evolution during the Cambrian, and then proclaiming that something magical must have occurred to bring all of this about — he’s suggesting a natural, environmental cause.

Let’s read on:

It was a massive greening of the planet by non-vascular plants, or primitive ground huggers, as Knauth calls them. This period, roughly 700 million years ago virtually set the table for the later explosion of life through the development of early soil that sequestered carbon, led to the build up of oxygen and allowed higher life forms to evolve.

We continue:

“During this period, Earth became extensively occupied by photosynthesizing organisms,” he [Knauth] added. “The greening was a key element in transforming the Precambrian world – which featured low oxygen levels and simple, bacteria dominant life forms – into the kind of world we have today with abundant oxygen and higher forms of plant and animal life.”

There’s more information in the press release. Not only that, but Knauth and his co-author Martin Kennedy, of the University of California, Riverside, will have an article on this in Nature.

It’ll be interesting to see the creationists’ response. There’s sure to be one. Stay tuned to this blog.

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