To doubt or not to doubt II

Teamwork: New York Times and Science Magazine Seek to Rebut Darwin's Doubt

Casey Luskin September 24, 2013 10:07 AM

 

 

 

It's now evident that, their previous denials notwithstanding, Darwin defenders have been unnerved by Darwin's Doubt. On the same day last week, both the world's top newspaper (the New York Times) and one of the world's top scientific journals (Science) turned their attention to the problem posed by Stephen Meyer. We'll respond later to the review of Darwin's Doubt in Science. For now, let's take a look at science-writer Carl Zimmer's piece in the Times, "New Approach to Explaining Evolution's Big Bang." Zimmer promotes the conclusions of a commentary in Science that accompanies the review of Meyer's book, purporting to explain the Cambrian explosion.

There's something odd about Zimmer's article. Despite the vigorous media dialogue over Darwin's Doubt, reflected in print, online, and over 300 Amazon reviews, Zimmer declines to mention the book or its author. But then the article in Science that claims to reveal the causes of the Cambrian explosion never acknowledges the controversy either. ENV noted a similar reticence in last week's Current Biology paper, which makes reference to "opponents of evolution," and critiques a very Meyer-esque argument, but likewise refuses to cite Meyer or Darwin's Doubt by name.

Zimmer endorses an approach to the Cambrian explosion, taken by M. Paul Smith and David A.T. Harper who wrote the Science commentary, that's often seen in papers on the subject. These papers cite a myriad of explanations, on the apparent assumption that just by tossing out a bunch of scattershot ideas, you've solved the problem. Carl Zimmer describes the method as follows:

Geologists suggested geological causes. Ecologists proposed ecological ones. Many of those ideas have merit, Dr. Smith and Dr. Harper argue in a commentary in this week's Science, but it's a mistake to search for a single cause. They propose that a tangled web of factors and feedbacks were responsible for evolution's big bang.

How did that work? Zimmer writes:

Long before the Cambrian explosion, Dr. Smith and Dr. Harper argue, one lineage of animals had already evolved the genetic capacity for spectacular diversity. Known as the bilaterians, they probably looked at first like little crawling worms. They shared the Precambrian oceans with other animals, like sponges and jellyfish. During the Cambrian explosion, relatively modest changes to their genes gave rise to a spectacular range of bodies.

But those genes evolved in bilaterians tens of millions of years before the Cambrian explosion put them to the test, notes Dr. Smith. "They had the capacity," he said, "but it hadn't been expressed yet."

Isn't that interesting -- bilaterians "evolved the genetic capacity for spectacular diversity," for no apparent reason, long before it was "expressed." The Science paper notes "an apparent > 100-million-year gap between the evolutionary innovation and its consequences"! For all that time, the "genetic capacity" sat on its hands, doing nothing. Then, thanks to sheer dumb luck, it turned out that the "innovation" was exactly what was necessary to evolve into all the diverse forms of animals we observe. The only thing missing was an environmental trigger.

The trouble is that, in Darwinian theory, you don't survive and reproduce based upon what will happen in the future. You survive and reproduce based upon what happens now. Darwinian evolution can't select for future goals, and thus could not evolve the "genetic capacity for spectacular diversity" in the future. Despite their theory, which was formulated to explain away the appearance of teleology in biology, Darwinians are being forced into increasingly teleological-sounding explanations for the Cambrian explosion. Not that Team Darwin is anywhere near to admitting that.

As Meyer explains in Darwin's Doubt, building new forms of animal life requires massive amounts of new biological information in the form of myriads of new genes, non-coding DNA regulatory elements, gene regulatory networks, and epigenetic information. He shows, for several separate reasons, that the neo-Darwinian mechanism lacks the creative capacity necessary to generate these various forms of information.

Recall, for example, that Meyer shows that that functional genes and proteins are exceedingly rare within sequence space. And, for this reason, he argues that a random mutational search will be overwhelmingly more likely to fail, than to succeed, in generating even a single new gene or protein during the entire history of life on earth. Similarly, he shows that mutations in DNA alone cannot produce the epigenetic ("beyond the gene") information necessary to build new animal body plans.

Does Zimmer, or the article in Science that he cites, address (or solve) these or any of the other problems that Meyer addresses? They don't.

But ID theorists pay close attention to the crucial question: Where does the information necessary to build a new animal come from? Zimmer and the scientists he writes about don't even ask that question.

They just assume the "genetic capacity" arose 100+ million years before it was "expressed" -- without providing any causal explanation for the origin of that information. In other words, they just assume an animal with all the necessary information to produce all future Cambrian animals. That's quite an assumption! Of course, once that information had arisen, all that was then required was some global environmental change to trigger "an evolutionary cascade that led to the rapid rise in diversity" (as the Science paper puts it). Because Earth's history is filled with geological changes and environmental catastrophes, such events aren't hard to find. Indeed, they're practically a dime a dozen. Here's what Zimmer finds:

It took a global flood to tap that capacity, Dr. Smith and Dr. Harper propose. They base their proposal on a study published last year by Shanan Peters of the University of Wisconsin and Robert Gaines of Pomona College. They offered evidence that the Cambrian Explosion was preceded by a rise in sea level that submerged vast swaths of land, eroding the drowned rocks.

I responded to Peters and Gaines's study last year -- and again this year. Because, puzzlingly, it continues to be cited, over and over. As I wrote:

Citing increased chemical weathering around the time of the Cambrian explosion doesn't explain the abrupt appearance of new genes and other genetic information needed to generate new body plans. If they expect us to believe that sedimentation rates explain the sudden origin of new body plans, then it would seem that the Cambrian explosion is still a "mystery."

Wait, there's more. "But these great floods also poisoned the ocean," Zimmer says, and "In order to survive, animals had to evolve ways to rid themselves of the poison." Are we about to hear an explanation for how new information arose? No:

One solution may have been to pack the calcium into crystals, which eventually evolved into shells bones, and other hard tissues. Dr. Smith doesn't think it's a coincidence that several different lineages of bilaterians evolved hard tissues during the Cambrian explosion, and not sooner.

According to this logic, increasing the level of "poison" (calcium) in water generates new information. From there, it's a snap:

These shells and other hard tissues sped up animal evolution even more. Predators could grow hard claws and jaws for killing prey, and their prey could evolve hard shells and spines to defend themselves. Animals became locked in an evolutionary arms race.

OK, I think I now understand why the Cambrian explosion happened. Here's the formula:

• First, the "genetic capacity" to produce all known animal forms arises without any adaptive benefit in some unknown hypothetical ancestral organism.


• Then it does nothing for some 100+ million years. (Nobody's sure exactly how long.)


• Then some environmental trigger adds selection pressure. Earth's history is full of options; choose one, or choose five. Zimmer's scientists choose chemical weathering + sea level rise + oxygenation of oceans.


• Then an "arms race" ensues, and all that untapped genetic information is suddenly "expressed," and boom goes the dynamite: numerous animal body plans appear in a geological blink-of-the-eye.

The Science commentary puts it more artfully: "Together, these interacting processes generated an evolutionary cascade that led to the rapid rise in diversity." And so, there you have it: Cambrian enigma solved -- provided of course that you don't ask any pesky questions about the origin of genetic or epigenetic information.