The Unmetabolized Darwin

A few weeks ago, I saw Darwin's name invoked in two separate articles in a single edition of The New York Times. One dwelled on a creationism controversy raging in a Midwestern state, while the other used the expression Darwinian in an offhand manner to allude to the dog-eat-dog competitiveness of the business world. I found it striking that, in both instances, it was Darwin, and not evolution, that was the key word. For in the beginning of the twenty-first century, it is Charles Robert Darwin who still stands out as the towering nineteenth-century intellectual figure who still gives modern society fits. Both Sigmund Freud and Karl Marx (to choose two others whose work also shook up Western society), though far from forgotten, after a good run have begun to fade from the front pages. Darwin recently replaced Charles Dickens on the British ten-pound note—ostensibly because his beard looks better, but in reality because he remains out front in our collective consciousness, increasingly alone among the voices of the past.

Why? Why does Darwin still bother so many of us in the Western world? Is it because Darwin's ideas of evolution are so difficult to understand? Or is it the very idea of evolution that is causing the problem?

The answer, of course, is the latter: the evolution of life through natural processes— and especially the recognition that our own species, Homo sapiens, is as inextricably linked to the rest of the living world as are redwood trees, mushrooms, sponges, and bacteria—still does not sit well with an awful lot of the citizenry of the United States and other Western countries. It is not that such skeptics are stupid—or even, at least in terms of their spokespersons, ill-informed. It's not, in other words, that creationists don't understand evolution: it's that they don't like it. Indeed, they revile it.

The reason that Darwin's name is still invoked so routinely is that social discourse on the cosmic origins of human beings has been stuck in a rut since the publication of his On the Origin of Species (1859). Roughly half of modern society at large grasps his point and is thereby able to understand why we look so much like chimps and orangutans—similar to the way people look at the matching shorelines of South

America and Africa and have no problem with the idea of continental drift. It seems commonsensical to this 50 percent of society to see us as the product of natural evolutionary processes—and when new facts come along, such as the astonishing 98.4 percent genetic similarity between humans and chimps, they seem to fit right in. These people have absorbed the evolutionary lesson and have moved on with their lives.

Darwin would be troubled but not especially surprised that the other roughly 50 percent of Americans (perhaps fewer numbers in his native England and on the European continent) still intransigently reject evolution. He had fully realized that life had evolved through natural selection—and that humans had evolved along with everything else—by the late 1830s. Yet, as is well known, Darwin pretty much kept his views a secret until virtually forced to "come out of the closet" and publish his views in the late 1850s by Alfred Russel Wallace's disclosure in a letter to Darwin that he had developed the same set of ideas. Darwin didn't want his earth-shattering idea to be scooped, so he hurriedly wrote the Origin—a book that sold out its initial print run on its first day of publication.

Although Darwin sometimes said that he waited twenty years to publish his ideas because he wanted to hone his concepts and marshal all the evidence he could (in itself a not-unreasonable claim), it is clear that the real reason for the delay was his fear of the firestorm of anger that his ideas were sure to unleash. His own wife was unhappy with his ideas; indeed, the marriage was almost called off when Darwin told her, against his father's advice, of his increasing religious doubts occasioned by his work. If Darwin's own faith was challenged by his conviction that life, including human life, had evolved through natural causes, he knew full well that the religiously faithful—nearly 100 percent of the population of Great Britain—would see his ideas in the very same stark terms. They too would see evolution as a challenge to the basic tenets of the Christian faith, and they would be very, very upset.

I agree with those historians who point to Darwin's nearly daily bouts with gastrointestinal upset as a manifestation of anxiety rather than of any systemic physical illness. Darwin finally did tell his new friend Joseph Hooker in 1844 a little bit about his secret ideas on evolution—telling him at the same time, though, that "it was like confessing a murder." Darwin knew he had the equivalent of the recipe for an atomic bomb, so devastating an effect would his ideas have on British society when he finally announced them. No wonder he was so hesitant to speak out; no wonder he was so anxious.

And, of course, his fears were well grounded. If it is the case that the majority of practitioners of the mainstream Judeo-Christian religions have had little problem concluding that it is the job of science to explain the material contents of the universe and how it works, and the task of religion to explore the spiritual and moral side of human existence, it nonetheless remains as true today as it was in the nineteenth century that a literal reading of Genesis (with its two and a half nonidentical accounts of the origin of the earth, life, and human beings) does not readily match up with the scientific account. There was a conflict then, and there remains a conflict today, between the scientific account of the history of earth and the evolution of life, on the one hand, and received interpretations of the same in some of the more hard-core Judeo-Christian sects. Darwin remains unmetabolized—the very reason that his name is still so readily invoked so long after he died in 1882.

Thus, it is not an intellectual issue—try as creationists will to make it seem so. Science—as many of the writings in this book make clear—cannot deal with the supernatural. Its rules of evidence require any statement about the nature of the world to be testable—to be subjected to further testing by asking the following: If this statement is true about the world, what would I expect to observe? If the predictions are borne out by experimentation or further observation, the idea is confirmed or corroborated—but never in the final analysis actually "proved." If, on the other hand, our predictions are not realized, we must conclude that our statement is in fact wrong: we have falsified it.

what predictions arise from the notion of evolution—that is, the idea that all organisms presently on Earth are descended from a single common ancestor? There are two major predictions of what life should look like if evolution has happened. As Darwin first pointed out, new features appearing within a lineage would be passed along in the same or further modified form to all its descendants—but would not be present in other lineages that had diverged prior to the appearance of the evolutionary novelty (Darwin knew that the idea of evolution must also include the diversification of lineages, simply because there are so many different kinds of organisms on earth). Thus the prediction: more closely related organisms share more similarities with each other than with more remotely related kin; rats and mice are more similar to each other than they are to squirrels; but rats and mice and squirrels (united as rodents) share more similarities than any of them share with cats. In the end, there should be a single nested set of similarities linking up all of life.

This is exactly what systematic biologists and paleontologists find as they probe the patterns of similarities held among organisms—in effect testing over and over again this grand prediction of evolution. Rats, squirrels, and mice share many similarities, but with all other animals—plus fungi and many microscopic forms of life— they share a common organization of their (eukaryotic) cells. They share even with the simplest bacteria the presence of the molecule RNA, which, along with the slightly less ubiquitous DNA, is the feature that is shared by all of life—and the feature that should be there if all life has descended from a single common ancestor.

Does this "prove" evolution? No, we don't speak of absolute proof, but we have so consistently found these predicted patterns of similarity to be there after centuries of continual research that scientists are confident that life has evolved.

The second grand prediction of the very idea of evolution is that the spectrum of simple (bacteria) to complex (multicellular plant and animal life) should be ordered through time: the earliest forms of life should be the simple bacteria; single celled eukaryotic organisms should come next in the fossil record—and only later do the more complex forms of multicellular life arrive. That is indeed what we do find: bacteria going back at least as far as 3.5 billion years; more complex cells perhaps 2.2 billion years; and the great "explosion" of complex animal life between five and six hundred million years—a rapid diversification that nonetheless has simpler animals (e.g., sponges and cnidarians [relatives of corals and sea anemones]) preceding more complex forms (like arthropods and mollusks). Among vertebrates, fishes preceded amphibians, which in turn preceded reptiles, which came, as would be expected, before birds and mammals.

Again, evolution is not proven—but it certainly is fundamentally and overwhelmingly substantiated by the failure to falsify this prediction of increasing complexity through time.

What do creationists have to refute the very idea of evolution? They trot out a mishmash of objections to specific scientific claims; to the extent that they are testable, creationists' ideas have long been refuted. More recently, they have reverted to notions of irreducible complexity and intelligent design—ideas presented as new, but actually part of the creationist war chest before Darwin ever published the Origin. The fact that organisms frequently display intricate anatomies and behaviors to perform certain functions—such as flying—has inspired the claim that there must be some intelligent designer behind it all, that a natural process like natural selection would be inadequate to construct such exquisite complexity.

There is, of course, no scientific way to test for the existence of the intelligent designer; on the other hand, we can study natural selection in the wild, in the laboratory, and in mathematical simulations. We can, however, ask whether patterns of history in systems that we know are intelligently designed—like cars, computers, or musical instruments—resemble those of biological history. I have actually done some work along these lines—and the answer, predictably and unsurprisingly, is that the evolutionary trees of my trilobites (the fossils I study) do not resemble the trees generated by the same program for my favorite man-made objects—the musical instruments known as cornets. The reason in a nutshell is obvious: the information in biological systems is transferred almost entirely "vertically" from parent to offspring via the DNA in sperm and egg; in man-made systems, like cornets, the information is spread as much "horizontally" (as when people copy other people's ideas) as it is vertically from old master to young pupil. The details of the history of man-made objects is invariably many times more complex than what biologists find for their organisms. I think the hypothesis of intelligent design, in this sense, is indeed falsifiable—and I think we have falsified it already.

But pursuit of scientific and intellectually valid truth is not really what creationism is all about. Creationism is about maintaining particular, narrow forms of religious belief—beliefs that seem to their adherents to be threatened by the very idea of evolution. In general, it should not be anyone's business what anyone else's religious beliefs are. It is because creationism transcends religious belief and is openly and aggressively political that we need to sit up and pay attention. For in their zeal to blot evolution from the ledger books of Western civilization, creationists have tried repeatedly for well over a hundred years to have evolution either watered down, or preferably completely removed, from the curriculum of America's public schools. Creationists persistently and consistently threaten the integrity of science teaching in America—and this, of course, is of grave concern.

Perhaps someday schools in the United States will catch up to those in other developed countries and treat evolution as a normal scientific subject. Before that happens, though, people need to understand evolution, and also understand the creationism and evolution controversy. Evolution vs. Creationism: An Introduction is a step toward this goal, and readers will indeed learn a great deal about the scientific, religious, educational, political, and legal aspects of this controversy. Then those of us lucky enough to study evolution as a profession won't be the only ones to appreciate this fascinating field of study.

Niles Eldredge Division of Paleontology The American Museum of Natural History

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