By Richard Dawkins
Creationists are deeply enamored of the fossil record, because they have been taught (by each other) to repeat, over and over, the mantra that it is full of "gaps": "Show me your 'intermediates!' " They fondly (very fondly) imagine that these "gaps" are an embarrassment to evolutionists. Actually, we are lucky to have any fossils at all, let alone the massive numbers that we now do have to document evolutionary history—large numbers of which, by any standards, constitute beautiful "intermediates." We don't need fossils in order to demonstrate that evolution is a fact. The evidence for evolution would be entirely secure even if not a single corpse had ever fossilized. It is a bonus that we do actually have rich seams of fossils to mine, and more are discovered every day. The fossil evidence for evolution in many major animal groups is wonderfully strong. Nevertheless there are, of course, gaps, and creationists love them obsessively.
Let's use the analogy of a detective coming to the scene of a crime where there were no eyewitnesses. The baronet has been shot. Fingerprints, footprints, DNA from a sweat stain on the pistol, and a strong motive, all point toward the butler. It's pretty much an open-and-shut case, and the jury and everybody in the court is convinced that the butler did it. But a last-minute piece of evidence is discovered, in the nick of time before the jury retires to consider what had seemed to be their inevitable verdict of guilty: somebody remembers that the baronet had installed spy cameras against burglars. With bated breath, the court watches the films. One of them shows the butler in the act of opening the drawer in his pantry, taking out a pistol, loading it, and creeping stealthily out of the room with a malevolent gleam in his eye. You might think that this solidifies the case against the butler even further. Mark the sequel, however. The butler's defense lawyer astutely points out that there was no spy camera in the library where the murder took place, and no spy camera in the corridor leading from the butler's pantry. "There's a gap in the video record! We don't know what happened after the butler left the pantry. There is clearly insufficient evidence to convict my client."
In vain, the prosecution lawyer points out that there was a second camera in the billiard room, and this shows, through the open door, the butler, gun at the ready, creeping on tiptoe along the passage toward the library. Surely this plugs the gap in the video record? But no. Triumphantly the defense lawyer plays his ace. "We don't know what happened before or after the butler passed the open door of the billiard room. There are now two gaps in the video record. Ladies and gentlemen of the jury, my case rests. There is now even less evidence against my client than there was before."
The fossil record, like the spy camera in the murder story, is a bonus, something that we had no right to expect as a matter of entitlement. There is already more than enough evidence to convict the butler without the spy camera, and the jury was about to deliver a guilty verdict before the spy camera was discovered. Similarly, there is more than enough evidence for the fact of evolution in the comparative study of modern species and their geographical distribution. We don't need fossils. The case for evolution is watertight without them, so it is paradoxical to use gaps in the fossil record as though they were evidence against evolution. We are lucky to have fossils at all.
What would be evidence against evolution, and very strong evidence at that, would be the discovery of even a single fossil in the wrong geological stratum. As J.B.S. Haldane famously retorted when asked to name an observation that would disprove the theory of evolution, "Fossil rabbits in the Precambrian!" No such rabbits, no authentically anachronistic fossils of any kind, have ever been found. All the fossils that we have, and there are very very many indeed, occur, without a single authenticated exception, in the right temporal sequence. Yes, there are gaps where there are no fossils at all, and that is only to be expected. But not a single solitary fossil has ever been found before it could have evolved. That is a very telling fact. A good theory is one that is vulnerable to disproof, yet is not disproved. Evolution could so easily be disproved if just a single fossil turned up in the wrong date order. Evolution has passed this test with flying colors. Skeptics of evolution who wish to prove their case should be diligently scrabbling around in the rocks, desperately trying to find anachronistic fossils. Maybe they'll find one. Want a bet?
The biggest gap, and the one the creationists like best of all, is the one that preceded the so-called Cambrian Explosion. A little more than half a billion years ago, in the Cambrian era, most of the great animal phyla "suddenly" appear in the fossil record. Suddenly, that is, in the sense that no fossils of these animal groups are known in rocks older than the Cambrian, not suddenly in the sense of instantaneously; the period we are talking about covers about 20 million years. Anyway, it is still quite sudden, and, as I wrote in a previous book, the Cambrian shows us a substantial number of major animal phyla "already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history. Needless to say, this appearance of sudden planting has delighted creationists."
The last sentence shows that I was savvy enough to realize that creationists would like the Cambrian Explosion. I was not (back in 1986) savvy enough to realize that they'd gleefully quote my lines back at me in their own favor, carefully omitting my careful words of explanation. On a whim, I just searched the World Wide Web for "It is as though they were just planted there, without any evolutionary history" and obtained no fewer than 1,250 hits. As a crude control test of the hypothesis that the majority of these hits represent creationist quote—minings, I tried searching, as a comparison, the clause that immediately follows the above quotation: "Evolutionists of all stripes believe, however, that this really does represent a very large gap in the fossil record." I obtained a grand total of 63 hits, compared to the 1,250 hits for the previous sentence.
I have dealt with the Cambrian Explosion at length before. Here I'll add just one new point, illustrated by the flatworms, Platyhelminthes. This great phylum of worms includes the parasitic flukes and tapeworms, which are of great medical importance. My favorites, however, are the free-living turbellarian worms, of which there are more than 4,000 species: that's about as numerous as all the mammal species put together. They are common, both in water and on land, and presumably have been common for a very long time. You'd expect, therefore, to see a rich fossil history. Unfortunately, there is almost nothing. Apart from a handful of ambiguous trace fossils, not a single fossil flatworm has ever been found. The Platyhelminthes, to a worm, are "already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history." But in this case, "the very first time they appear" is not the Cambrian but today. Do you see what this means, or at least ought to mean for creationists? Creationists believe that flatworms were created in the same week as all other creatures. They have therefore had exactly the same time in which to fossilize as all other animals. During all the centuries when all those bony or shelly animals were depositing their fossils by the millions, the flatworms must have been living happily alongside them, but without leaving the slightest trace of their presence in the rocks. What, then, is so special about gaps in the record of those animals that do fossilize, given that the past history of the flatworms is one big gap: even though the flatworms, by the creationists' own account, have been living for the same length of time? If the gap before the Cambrian Explosion is used as evidence that most animals suddenly sprang into existence in the Cambrian, exactly the same "logic" should be used to prove that the flatworms sprang into existence yesterday. Yet this contradicts the creationist's belief that flatworms were created during the same creative week as everything else. You cannot have it both ways. This argument, at a stroke, completely and finally destroys the creationist case that the Precambrian gap in the fossil record can be taken as evidence against evolution.
Why, on the evolutionary view, are there so few fossils before the Cambrian era? Well, presumably, whatever factors applied to the flatworms throughout geological time to this day, those same factors applied to the rest of the animal kingdom before the Cambrian. Probably, most animals before the Cambrian were soft-bodied like modern flatworms, probably rather small like modern turbellarians—just not good fossil material. Then something happened half a billion years ago to allow animals to fossilize freely—the arising of hard, mineralized skeletons, for example.
An earlier name for "gap in the fossil record" was "missing link." The phrase enjoyed a vogue in late Victorian England, and on into the 20th century. Inspired by a misunderstanding of Darwin's theory, it was used as an insult, in roughly the same way as "Neanderthal" is colloquially (and unjustly) used today.
The original meaning, a confused one, implied that the Darwinian theory lacked a vital link between humans and other primates. History-deniers, to this day, are very fond of saying, in what they imagine is a taunting tone of voice: "But you still haven't found the missing link," and they often throw in a gibe about Piltdown man, for good measure. Nobody knows who perpetrated the Piltdown hoax, but he has a lot to answer for. The fact that one of the first candidates for a man-ape fossil to be discovered turned out to be a hoax provided an excuse for history-deniers to ignore the very numerous fossils that are not hoaxes; and they still haven't stopped crowing about it. If only they would look at the facts, they'd soon discover that we now have a rich supply of intermediate fossils linking modern humans to the common ancestor that we share with chimpanzees. On the human side of the divide, that is. Interestingly, there are as yet no fossils linking that ancestor (which was neither chimpanzee nor human) to modern chimpanzees. Perhaps this is because chimpanzees live in forests, which don't provide good fossilizing conditions. If anything, it is chimpanzees, not humans, who today have a right to complain of missing links!
Another meaning concerns the alleged paucity of so-called "transitional forms" between major groups like reptiles and birds, or fish and amphibians. "Produce your intermediates!" Evolutionists often respond to this challenge from history-deniers by throwing them the bones of Archaeopteryx, the famous "intermediate" between "reptiles" and birds. This is a mistake. Archaeopteryx is not the answer to a challenge, because there is no challenge worth answering. To put up a single famous fossil like Archaeopteryx panders to a fallacy. In fact, for a large number of fossils, a good case can be made that every one of them is an intermediate between something and something else.
The silliest of all these "missing link" challenges are the following two (or variants of them, of which there are many). First, "If people came from monkeys via frogs and fish, then why does the fossil record not contain a 'fronkey'?" And, second, "I'll believe in evolution when I see a monkey give birth to a human baby." This last one makes the same mistake as all the others, plus the additional one of thinking that major evolutionary change happens overnight.
Well, of course, monkeys are not descended from frogs. No sane evolu-tionist ever said they were, or that ducks are descended from crocodiles or vice versa. Monkeys and frogs share an ancestor, which certainly looked nothing like a frog and nothing like a monkey. Maybe it looked a bit like a salamander, and we do indeed have salamander-like fossils dating from the right time. But that is not the point. Every one of the millions of species of animals shares an ancestor with every other one. If your understanding of evolution is so warped that you think we should expect to see a fronkey and a crocoduck, you should also wax sarcastic about the absence of a doggypotamos and an elephanzee. Indeed, why limit yourself to mammals? Why not a kangaroach (intermediate between kangaroo and cockroach) or an octopard (intermediate between octopus and leopard)? There's an infinite number of animal names you can string together in that way. Of course hippopotamuses are not descended from dogs, or vice versa. Chimpanzees are not descended from elephants or vice versa, just as monkeys are not descended from frogs. No modern species is descended from any other modern species (if we leave out very recent splits). Just as you can find fossils that approximate to the common ancestor of a frog and a monkey, so you can find fossils that approximate to the common ancestor of elephants and chimpanzees.
As for the second challenge, once again, humans are not descended from monkeys. We share a common ancestor with monkeys. As it happens, the common ancestor would have looked a lot more like a monkey than a man, and we would indeed probably have called it a monkey if we had met it, some 25 million years ago. But even though humans evolved from an ancestor that we could sensibly call a monkey, no animal gives birth to an instant new species, or at least not one as different from itself as a man is from a monkey, or even from a chimpanzee. That isn't what evolution is about. Evolution not only is a gradual process as a matter of fact; it has to be gradual if it is to do any explanatory work. Huge leaps in a single generation—which is what a monkey giving birth to a human would be—are almost as unlikely as divine creation, and are ruled out for the same reason: too statistically improbable. It would be so nice if those who oppose evolution would take a tiny bit of trouble to learn the merest rudiments of what it is that they are opposing.
Excerpted from The Greatest Show on Earth: The Evidence for Evolution, by Richard Dawkins. © 2009 by Richard Dawkins.
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