It was not one of my finer moments. I was on my junior high school’s basketball team and we were headed out for an away game. As we boarded the bus, the cheerleaders handed everyone an apple as a pre-game snack. Being in seventh grade meant I was relegated to the back of the bus where the exhaust fumes were especially bad that day. So after eating my apple, I pulled my shirt up over my nose in the hopes of filtering out some of the noxious odors. That move was my undoing.
The combination of the recently consumed apple, the exhaust, and the winding road pushed me over the edge. Soon I was feeling nauseous. And then the unthinkable happened—I threw up inside my shirt. I don’t know what was worse: the vomit all over my chest or the teasing that predictably ensued.
Everyone is embarrassed by something. And many creationists think that evolutionary biologists should be mortified by the gaps in the fossil record. But as Richard Dawkins writes in The Greatest Show on Earth, the fossil record is of no concern to evolutionary biologists in the least. In fact, Dawkins considers the fossil record as evidence for biological evolution—in spite of ridicule from the creationist camp about all the “missing links.”
He discusses this point in chapter six of The Greatest Show on Earth. This week I continue my chapter-by-chapter critique of his latest book in which he offers what he considers the best evidence for the evolutionary paradigm. (Go here, here, here, and for comments on previous chapters.)
Dawkins admits there are gaps in the fossil record. But, he argues (and I would agree with his point), these gaps are to be expected given the vagaries of the burial and fossilization process. In fact, in some respects it is surprising that we have any fossils at all. According to Dawkins, creationists make much out of nothing when they use this point to deride the evolution.
He further asserts that the presence or absence of fossils is immaterial. From his standpoint, the case for biological evolution is so strong that a fossil record is not needed to establish the validity of evolution. Having fossils is a bonus. He then argues that the fossils we do possess provide powerful support for an evolutionary history of life, citing a number of examples presumably meant to document the evolution of major groups. Dawkins chooses to focus on the evolutionary transitions that allegedly occurred when vertebrates moved from the water to land with the origin of tetrapods, and then back to the water in the case of whales, seals, and turtles.
I think Dawkins is wrong in his claim that the fossil record is not needed to establish the validity of biological evolution (macroevolution). Without an abundant fossil record, how is it possible to maintain that evolution is a fact? The preserved history of life provides the means to conduct a time-based assessment of Darwin’s idea. If evolution is understood as change in life’s history over time driven by the forces of selection, then time-based data is necessary to cement this idea’s legitimacy.
Darwin discovered a mechanism that accounts for microevolution, speciation, and the evolution of microbes. But does the same mechanism apply to large-scale biological changes? We know that selection operating on genetic variation explains small evolutionary changes because we can observe them in real time. As I have pointed out before, there are reasons to think this mechanism is limited to small-scale changes because work in artificial selection exposes nonnegotiable biological boundaries.
In order to prove that selection can yield large-scale biological innovation, we need some type of time-based observation. Of course, we can’t observe macroevolutionary changes directly, but in principle we can witness these changes from the fossil record, which serves as a proxy for life’s history—a history that should be characterized by certain features and patterns if macroevolution is indeed a fact.
In many respects, there are gaps in knowledge in every scientific discipline. The real questions are: Can we discern the actual trends in life’s history from the fossil record despite the gaps? And is the fossil record an adequate enough sampling to evaluate predictions made by Darwin’s theory? Many paleontologists think so.
Rather than revealing gradual evolutionary transformations as expected based on Darwin’s mechanism, life’s history is dominated by explosive appearances every time biological innovation occurs. Biologist Eugene Koonin has termed these dramatic innovations as “big bang” events. These big bangs include: the origin of cells, the origin of archaea, bacteriea, and eukarya, and the origin of animal body plans. (Go here to read an article I wrote about Koonin’s idea.) Gaps in the fossil record aren’t the problem for evolution, it’s the pattern of discontinuities and explosive innovations, a pattern I think better fits within a creation model.
But what about the examples Dawkins cites of evolutionary transformations at the water’s edge? These changes appear to be described by a series of transitional fossils. Given the incompleteness of the fossil record, aren’t these examples sufficient to establish evolution’s validity?
At first glance the origin of tetrapods, seals, and whales appear as remarkable examples of a transitional sequence in the fossil record. But careful consideration of the details identifies problems for the evolutionary framework. (Go here and here to read two articles I wrote about problems with the evolutionary account of tetrapod origins, and go here and here to listen to an episode of Science News Flash in which I discuss the evolutionary model for the origin of, whales and seals, respectively.)
One Final Point
In chapter six Dawkins also discusses a statement by famous biologist J. B. S. Haldane. As the story goes, Haldane was asked to identify an observation that would invalidate the theory of evolution. In reply, he quipped, “Fossil rabbits in the Precambrian!”
In other words, if fossils appeared out of order in the geological column, then the theory of evolution can’t be true. But Dawkins goes on to elaborate that there is “not a single solitary fossil [that] has ever been found before it could evolve.”
Evolutionary biologists often use this argument to defend their point of view. Yet I don’t buy it. In my opinion, this is a form of circular reasoning. We know that there aren’t rabbits in the Precambrian because we’ve never found rabbits in these geological layers. If rabbits were found in the Precambrian, then we would know that they existed during that time of Earth’s history.
There is nothing in the theory of evolution that tells us when organism should emerge. We know complex animal life appeared on Earth about 540 million years ago (mya) because the fossil record tells us so. We know that bony fish appear in the Ordovician because that’s what the fossil record shows. We know that dinosaurs appeared on Earth about 225 mya and became extent 65 mya because the fossil record indicates it.
Apart from the record provided by the fossil record, we wouldn’t have any knowledge of what past life on Earth looked like. Nor would we know anything about the timing and order of the appearance and disappearance of life-forms. Evolutionary biologists interpret the history of life from an evolutionary perspective and try to use their paradigm to explain the fossil record. But the theory of evolution can’t make predictions as to when life-forms should appear in Earth’s history. If rabbits were found in the Precambrian, Haldane and other evolutionary biologists most certainly wouldn’t abandon the evolutionary framework. Instead they would modify the theory to accommodate the appearance of rabbits at that point in time.
The fact of the matter is that there are “rabbits-in-the-Precambrian” examples in the fossil record that justifiably falsify the evolutionary paradigm. One that I’ve pointed out is the co-occurrence of vertebrates, chordates, urochordates, hemichordates, and echinoderms at the base of the Cambrian explosion. (Go here and here for previous articles.)
According to the evolutionary model, echinoderms produced hemichordates and urochordates as two separate evolutionary branches. Urochordates gave rise to chordates which, in turn, generated the jawless fish as the first vertebrates. In reality, fossils representative of these phyla show up simultaneously at the base of the Cambrian explosion. In other words, the fossils of jawless fish, chordates, urochordates, and hemichordates are out of sequence. If evolutionary biologists are sincere about the criterion for falsification laid down by Haldane, then good reason to abandon the evolutionary framework does exist.
The features that define the fossil don’t match the expectations based on Darwin’s mechanism. But the fossilized history of life on Earth is a bonus—a bonus for creationism.