New Understanding of Precambrian Fossil Tracks Makes Biology’s Big Bang More Explosive
I have three teenage daughters. They are good kids, but—as all teenagers are apt to do—they occasionally try to get by with things they shouldn’t. Usually when my wife or I suspect that something is amiss, my daughters will try to talk their way out of it by coming up with a story to defuse our suspicions. Still, it’s usually pretty easy to figure out that things are not on the up and up when all the facts don’t match their explanation.
This is also the case when it comes to the theory of biological evolution. Evolutionary biologists have constructed reasonably plausible scenarios to account for life’s origin and history through strictly mechanistic natural processes. But the facts don’t always match their explanations. The chief example of this is the Cambrian explosion. (For some articles on the problems that this dramatic event in life history creates for the evolutionary paradigm, go here, here, here, and here.)
Known in Darwin’s time, the Cambrian explosion refers to the dramatic appearance of complex animal life in the fossil record about 540 million years ago. Within a short period of time—perhaps less than 5 million years—anywhere from 50 to 80 percent of all animal phyla to ever exist on Earth appeared. The animals that came into existence during the Cambrian explosion were marine creatures. Instead of relatively simple organisms originating at the base of the Cambrian and then evolving toward increased intricacy, complex animals appear suddenly. The traditional evolutionary explanation argues that life should transition from simple to complex in a gradual, branching, tree-like fashion. On the other hand, such explosive appearances are exactly what should be expected if a Creator is responsible for orchestrating life’s history.
Like guilty teenagers confronted with evidence that exposes their explanation, evolutionary biologists try to change their story. This has surely been the case with regard to the Cambrian explosion, as scientists have tried to come up with alternative scenarios to explain away the devastating implications of the Cambrian event for the evolutionary model.
New work published in the journal Current Biology, however, eliminates one of the best counterexplanations that evolutionary biologists have mustered for the Cambrian explosion, making it even less likely that the facts surrounding “biology’s big bang” can be explained away.
The Cambrian Explosion and Darwin
When Darwin wrote On the Origin of Species, he was careful to acknowledge problems with his theory. One of those problems centered on the Cambrian explosion. Darwin wrote:
There is another and allied difficulty, which is much more serious. I allude to the manner in which species belonging to several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks… To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the Cambrian system, I can give no satisfactory answer.
Darwin was referring to the fact that geologists of his time recognized that no fossils of complex animal forms existed in rock formations older than 545 million years. Yet, rocks from the Cambrian time frame (545-485 million years ago) are replete with such remains.
He sidestepped this problem by arguing that the fossil record was incomplete and poorly studied. He expected that as paleontologists collected and analyzed fossils over time, the missing transitional forms and gradual evolutionary transformations would be uncovered. Over the last 150 years, paleontologists have indeed uncovered a treasure trove of fossils that document a rich history of life on Earth.
A Brief Description of Life’s History
The fossil record indicates that prior to about 570 million years ago life on Earth appears to have been dominated by single-celled organisms. At that point an event known as the Avalon Explosion took place. During this origins event, an enigmatic fauna of complex marine creatures known as the Ediacarans appeared. The Ediacaran fauna consisted of about 270 species that have been recovered as fossils in about thirty localities around the world. The organisms disappeared shortly before the Cambrian explosion. New research indicates that Ediacaran fauna emerged explosively, in the same manner as that of the Cambrian event.* During the Avalon explosion the full range of anatomical characteristics displayed by the Ediacarans was already expressed around 570 million years ago. In other words, no evolutionary buildup of biodiversity.
While some of the Ediacaran organisms persist into the Cambrian and a few may have connections to organisms that appear in the Cambrian explosion, most do not. For the most part, the Ediacaran fauna disappears right before the Cambrian explosion.
After the Ediacaran organisms became extinct, the Cambrian explosion took place and represents the first appearance of animal life as we know it today. The last century-and-a-half of research into the fossil record has failed to uncover the missing fossils that Darwin lamented.
A Possible Loop-Hole
While some paleontologists agree that the Cambrian explosion is a real, but enigmatic event—at least enigmatic from an evolutionary vantage point—others argue along Darwin’s famous line. They maintain that the Cambrian explosion is an artifact of an incomplete fossil record. In other words, there is a vast evolutionary history that is invisible because the first, simplest multicellular life-forms weren’t preserved in the fossil record.
To support this appeal to the fossil record’s incompleteness, evolutionary biologists point to trace fossils found in rocks as old as 2.1 billion years in age.
These fossils have been interpreted as tracks produced by complex multicellular animals that were the evolutionary precursors to the organisms that emerged in the Cambrian explosion. These trace fossils are typically characterized as a sinuous groove cut into the ground with a central ridge. The groove is bounded by two lateral ridges. Presumably, these traces were produced by an animal capable of movement that possessed bilateral symmetry
A Surprising New Insight about Trace Fossils
This interpretation, though reasonable, doesn’t appear to be correct based on recent work done by a team of oceanographers and biologists. These scientists were diving near the Little San Salvador Island of the Bahamas and noticed tracks on the ocean floor that were identical to the trace fossils ascribed to the movements of ancient complex animal life thought to have lived well before the Cambrian explosion.
To their surprise, the tracks looked as if they were produced by a large single-celled creature called Gromia sphaerica. The researchers surmised that the tracks resulted from the rolling movement of this organism.
This find means that the trace fossils in ancient rock formations older than 540 million years were likely not created by complex, multicellular animals, but instead by single-celled organisms like G. sphaerica. This discovery eliminates one of the most compelling counter-explanations that evolutionary biologists give for the validity of the Cambrian explosion. In spite of evolutionary biologists’ story, it looks like the best way to account for the facts associated with the origin of animal life is through the work of a Creator.
*For a discussion of the latest insights into the Avalon explosion see the booklet 10 Breakthroughs of 2008