To Create Cambrian Animals, Whack the Earth from Space - Evolution News & Views

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To Create Cambrian Animals, Whack the Earth from Space

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It's surely not a coincidence that this season in science-journal publishing we've seen a variety of attempts to solve the enigma that Stephen Meyer describes in his new book, Darwin's Doubt. The problem, of course, is how to account for the geologically sudden eruption of complex new life forms in the Cambrian explosion. Meyer argues that the best explanation is intelligent design.

The orthodox materialist camp in mainstream science remains in full denial mode. They can't stomach the proposal of ID, but neither can they for the most part bring themselves to answer Meyer by name, or even admit there's a controversy on the subject. Charles Marshall, reviewing the book in Science, is the honorable exception. So we get what look like stealth responses to Meyer's book that claim to have figured out the Cambrian puzzle without telling you what the urgency for doing so really is, thus evading the task of responding to Meyer directly. (See David Klinghoffer's review of the reviewers of Darwin's Doubt, "A Taxonomy of Evasion.")

Probably the most hopeless solution so far ascribes some of the creative power to a blast in the ocean by a space impact. This supposedly helped "set the stage" for the rapid proliferation of new animal forms. When we examine the complexity of a single Cambrian fossil, though, such a notion, like the others on offer, leaves all the important questions unanswered.

To his credit, Grant M. Young, the author of the proposal, is somewhat modest in the way he formulates his idea. His paper in GSA Today is primarily concerned with looking for evidence of a "very large marine impact" prior to the Ediacaran Period that sent vast quantities of water and oxygen into the atmosphere, changed the obliquity of Earth's orbit, and altered sea levels. The aftermath of that catastrophe, he speculates, played a role in the Cambrian explosion -- but a "crucial" one.

Attendant unprecedented environmental reorganization may have played a crucial role in the emergence of complex life forms. (Emphasis added.)

That's all Young had to say about it, but the suggestion was enough for NASA's Astrobiology Magazine to jump on it with a breathless headline: "Did a Huge Impact Lead to the Cambrian Explosion?" Author Johnny Bontemps catapulted that tease into the notion that "The ensuing environmental re-organization would have then set the stage for the emergence of complex life." Bontemps is correct about one thing:

These events marked the beginning of another drastic event known as the Cambrian explosion. Animal life on Earth suddenly blossomed, with all of the major groups of animals alive today making their first appearance.

Let's take a look at just one of the Cambrian animals, as seen in an exquisitely preserved new fossil from the Chengjiang strata in China, where so many beautiful fossils have been found (examples are shown in the Illustra film Darwin's Dilemma). The new fossil, Alalcomenaeus, published by Nature, was furnished with multiple claws like other Cambrian arthropods, but was so well preserved its nervous system could be outlined in detail. Even though it is dated from the early Cambrian at 520 million years old, it already had the nerves of modern spiders. Co-author Nick Strausfeld explains:

"We now know that the megacheirans had central nervous systems very similar to today's horseshoe crabs and scorpions," said Strausfeld, the senior author of the study and a Regents' Professor in the UA's Department of Neuroscience. "This means the ancestors of spiders and their kin lived side by side with the ancestors of crustaceans in the Lower Cambrian."'

Though tiny (about an inch long), its nervous system must have been fairly advanced, because the elongated creature was capable of swimming or crawling or both. In addition to about a dozen body segments with jointed appendages, it had a "pair of long, scissor-like appendages attached to the head, most likely for grasping or sensory purposes." It also had two pairs of eyes.

Iron deposits selectively accumulated in the nerve cells, allowing the research team to reconstruct the highly organized brain and nervous system. After processing with CT scans and iron scans, "out popped this beautiful nervous system in startling detail."

Comparing the outline of the fossil nervous system to nervous systems of horseshoe crabs and scorpions left no doubt that 520-million-year-old Alalcomenaeus was a member of the chelicerates.

Specifically, the fossil shows the typical hallmarks of the brains found in scorpions and spiders: Three clusters of nerve cells known as ganglia fused together as a brain also fused with some of the animal's body ganglia. This differs from crustaceans where ganglia are further apart and connected by long nerves, like the rungs of a rope ladder.

Other diagnostic features include the forward position of the gut opening in the brain and the arrangement of optic centers outside and inside the brain supplied by two pairs of eyes, just like in horseshoe crabs.

Horseshoe crabs survive as "living fossils" to this day, as residents near the Great Lakes know from the annual swarms. This fossil resembles modern chelicerates, one of the largest subphyla of arthropods, including horseshoe crabs, scorpions, spiders, mites, harvestmen, and ticks. Live Science adds, "The discovery of a fossilized brain in the preserved remains of an extinct 'mega-clawed' creature has revealed an ancient nervous system that is remarkably similar to that of modern-day spiders and scorpions."

Since crustaceans and chelicerates have both been found in the early Cambrian, Darwinian evolutionists are forced to postulate an unknown ancestor further back in time: "They had to come from somewhere," Strausfeld remarks. "Now the search is on." That sounds like the same challenge Charles Darwin gave fossil hunters 154 years ago to find the ancestors of the Cambrian animals.

The difficulty? It requires many different tissue types and interconnected systems to operate a complex animal like Alalcomenaeus, with its body segments, eyes, claws, mouth parts, gut and nervous system with a brain, to say nothing of coordinating the developmental programs that build these systems from a single cell. That is the major problem that Stephen Meyer emphasizes in Darwin's Doubt: where does the information come from to build complex body plans with hierarchical levels of organization?

Slamming a space rock at the Earth is hardly a plausible source of information. Meyer has been answering in detail the most serious and scholarly critique of his book, by Charles Marshall, refuting Marshall's criticisms point by point. Meanwhile the proposed alternative explanations for the Cambrian event keep coming, bearing increasingly the marks of desperation.

Image credit: NASA.