Jerry Coyne

Jerry Coyne

2/12/2009 @ 11:44AM

Why Evolution Is True

Michael Egnor is a neurosurgeon at the State University of New York at Stony Brook. For the sake of his patients, one must hope that he understands the brain’s anatomy better than its provenance. In an article on this site, “A Neurosurgeon, Not A Darwinist,” he claims that the theory of evolution is bogus.

After studying Darwinism, Egnor apparently discovered that “claims of evolutionary biologists go wildly beyond the evidence.” Indeed, he says, the only way complex biological systems such as biochemical pathways could have arisen is via direct divine intervention. Egnor concludes that “Darwinism itself is a religious creed that masquerades as science”–”atheism’s creation myth.”

While Egnor’s misguided attack on evolution tells us nothing about the truth of Darwinism, it does prove one thing: Doctors aren’t necessarily scientists. Some, like Egnor, seem completely unable to evaluate evidence. Why does he so readily dismiss a theory that has been universally accepted by scientists for over a century?

Apparently because a rather old book, Michael Denton’s Evolution: A Theory in Crisis, first published in 1985, convinced him that evolutionary theory was underlain by very weak evidence. If Egnor had bothered to look just a little into Denton’s book and its current standing, he would have learned that the arguments in it have long since been firmly refuted by scientists. Indeed, they were recanted by Denton himself in a later book more than 10 years ago.

Since Egnor is decades out of date and shows no sign of knowing anything at all about evolutionary biology in the 21st century, one wonders what could have inspired his declaration at this time.

The tenets of evolutionary theory are simple: Life evolved, largely under the influence of natural selection; this evolution took a rather long time; and species alive and dead can be organized on the basis of shared similarities into a tree whose branching pattern implies that every pair of living species has a common ancestor.

Among genuine scientists, there is not the slightest doubt about the truth of these ideas. In contrast to Egnor’s claim, the evidence for all of them is not only strong but copious–so much so that evolution has graduated from a scientific theory to a scientific fact.

My recent book, Why Evolution Is True, gives 230 pages of evidence for evolution–evidence from many areas of biology, including the fossil record, anatomy, biogeography and molecular biology. My main problem in writing the book was not deciding what to present, but what to leave out; I could easily have made it three times longer without even beginning to exhaust the data. There is so much evidence and so many kinds of evidence that one would have to be either willfully ignorant or blinded by faith to think otherwise. (I leave it to the reader to judge to which category Egnor belongs.)

Let’s examine Egnor’s main criticism of evolutionary theory. “The fossil record,” he writes, “shows sharp discontinuity between species, not the gradual transitions that Darwinism inherently predicts.”

This is sheer nonsense. As all biologists know, we have many examples not only of gradual change within species but also of “transitional forms” between very different kinds of species. These include fossil links between fish and amphibians, reptiles and birds, reptiles and mammals and, of course, the famous fossils linking apelike creatures with our own species, Homo sapiens. Does Egnor not know this, or is he simply trying to mislead the reader?

Another specious claim is his assertion that “Darwin’s theory offers no coherent, evidence-based explanation for the evolution of even a single molecular pathway from primordial components.” Nonsense–even the complicated pathway of blood clotting (an example much favored by creationists) is the subject of coherent, evidenced-based explanations.

Egnor also declares that “intricate biomolecules such as enzymes are so functionally complex that it’s difficult to see how they could arise by random mutations.” He is right here: such complex adaptations could not have arisen under the power of random mutation alone.

What he seems to have forgotten is the process of natural selection, which filters those mutations, preserving the good ones and eliminating the bad ones. It is the combination of mutation and the selection filter that produces the extraordinary instances of adaptation we can document in nature. Bacteria, for example, evolved brand-new enzymes to break down nylon–an artificial polymer that was never encountered by bacteria before 1930.

How does Egnor account for the natural world? He does not, in fact, offer a scientific theory. Rather, he subscribes to the creationist view that complex things, which are difficult to explain, are the domain of God. If we don’t understand something, there’s no point trying to understand it–we should just throw up our hands and say, “God did it.”

Imagine what would have happened if, over the history of science, we imputed to God’s hand everything we didn’t understand. We would never have cured the plague, which–like most diseases and disasters–was once thought to reflect God’s anger rather than bacteria-carrying fleas. “Barrenness” in women was thought to reflect divine displeasure; it is now treated effectively by scientific means, not by propitiating the gods.

There are no observations in nature that refute Darwinism, but there are plenty that refute Egnor’s creationist alternative. How does he explain the persistence of “dead genes” in species (like our own broken one for making vitamin C)–genes that were functional in our ancestors? What explains those annoying hominin fossils that span the gap from early apelike creatures to modern humans? Why do human fetuses produce a coat of hair after six months in the womb, and then shed it before birth? Why didn’t the creator stock oceanic islands with mammals, reptiles and amphibians? Why did He give us vestigial ear muscles that have no function? Why do whales occasionally sprout hind legs? Did God design all creatures to fool us into thinking that they evolved?

The good news is that Egnor is just one benighted physician. Far more disturbing is Forbes’ ham-handed policy of “balancing” the views of evolutionists by giving a say to Egnor and four other creationists. (Their articles, found here, are at least as misleading as Egnor’s.) Perhaps Forbes sees Darwinism as “controversial.” But it’s not, at least not in a scientific sense. Scientifically, evolution is a settled issue–a fact.

The only “controversy” is social and political: Will Americans, in violation of the First Amendment of the Constitution, be allowed to impose a false, religiously based view of biology in the public schools? This “teach the controversy” approach, so popular among fundamentalists, ill suits a publication with the gravitas of Forbes.

Can we expect that it will balance stories on medicine with the competing views of shamans, Christian Scientists and spiritual healers? Will articles on the Holocaust be rebutted by the many Holocaust deniers? When the 40th anniversary of the first moon landing rolls around this July, will Forbes give a say to paranoids who think the landing was a fraud, staged on a movie lot?

This, in effect, is what Forbes has done by giving equal time to evolution-deniers. Journalists have an obligation to be fair, but this doesn’t mean that they must give charlatans a prestigious platform from which to broadcast their lies. By doing so, Forbes has debased both journalism and science.

Jerry A. Coyne is a professor in the department of ecology and evolution at the University of Chicago. His latest book is Why Evolution is True, published by Viking.

Comments are turned off for this post.