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"...Given the copious evidence for evolution, it seems unlikely that it will be replaced by an alternative theory. But that is exactly what intelligent-design creationists are demanding. Is there some dramatic new evidence, then, or some insufficiency of neo-Darwinism, that warrants overturning the theory of evolution?
The question is worth asking, but the answer is no. Intelligent design is simply the third attempt of creationists to proselytize our children at the expense of good science and clear thinking. Having failed to ban evolution from schools, and later to get equal classroom time for scientific creationism, they have made a few adjustments designed to sneak Christian cosmogony past the First Amendment. And these adjustments have given ID a popularity never enjoyed by earlier forms of creationism. Even the president of the United States has lent a sympathetic ear: George W. Bush recently told reporters in Texas that intelligent design should be taught in public schools alongside evolution because "part of education is to expose people to different schools of thought." Articles by IDers, or about their "theory," regularly appear in mainstream publications such as The New York Times.
Why have the new image and the new approach been more successful? For a start, IDers have duped many people by further removing God from the picture, or at least hiding him behind the frame. No longer do creationists mention a deity, or even a creator, but simply a neutral-sounding "intelligent designer," as if it were not the same thing. This designer could in principle be Brahma, or the Taoist P'an Ku, or even a space alien; but ID creationists, as will be evident to anybody who attends to all that they say, mean only one entity: the biblical God. Their problem is that invoking this deity in science classes in public schools is unconstitutional. So IDers never refer openly to God, and people unfamiliar with the history of their creationist doctrine might believe that there is a real scientific theory afoot. They use imposing new terms such as "irreducible complexity," which make their arguments seem more sophisticated than those of earlier creationists.
In addition, many IDers have more impressive academic credentials than did earlier scientific creationists, whose talks and antics always bore a whiff of the revival meeting. Unlike scientific creationists, many IDers work at secular institutions rather than at Bible schools. IDers work, speak, and write like trained academics; they do not come off as barely repressed evangelists. Their ranks include Phillip Johnson, the most prominent spokesperson for ID, and a retired professor of law at the University of California, Berkeley; Michael Behe, a professor of biochemistry at Lehigh University; William Dembski, a mathematician-philosopher and the director of the Center for Theology and Science at Southern Baptist Theological Seminary; and Jonathan Wells, who has a doctorate in biology from Berkeley.
All of these proponents, save Johnson, are senior fellows at the Center for Science and Culture (CSC), a division of the Discovery Institute, which is a conservative think tank in Seattle. (Johnson is the "program advisor" to the CSC.) The CSC is the nerve center of the intelligentdesign movement. Its origins are demonstrably religious: as described by the Discovery Institute, the CSC was designed explicitly "to defeat scientific materialism and its destructive moral, cultural, and political legacies" and "to replace materialistic explanations with the theistic understanding that nature and human beings are created by God." Between them, these IDers have published more than a dozen books about intelligent design (Johnson alone has produced eight), which in turn have provoked numerous responses by scientists. Let us examine one of their most influential volumes, the textbook called Of Pandas and People . This is the book recommended by the Dover school district as a "reference book" for students interested in learning about intelligent design.
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Of Pandas and People is a textbook designed as an antidote to the evolution segment of high school biology classes. It was first published in 1989. By repackaging and updating a subset of traditional young-earth creationist arguments while avoiding taking a stand on any issues that might divide creationists (such as the age of the Earth), it marked the beginning of the modern intelligent design movement. By presenting the case for ID, it is supposedly designed to give students a "balanced perspective" on evolution. Although the second edition of Pandas is now twelve years old (a third edition, called Design of Life, is in the works), it accurately presents to students the major arguments for ID.
Pandas carefully avoids mentioning God (except under aliases such as "intelligent designer," "master intellect," and so on); but a little digging reveals the book's deep religious roots. One of its authors, Percival Davis, wrote explicitly about his religious beliefs in his book A Case for Creation, co-authored with Wayne Frair: "Truth as God sees it is revealed in the pages of Scripture, and that revelation is therefore more certainly true than any human rationalism. For the creationist, revealed truth controls his view of the universe to at least as great a degree as anything that has been advanced using the scientific method." Its other author, Dean Kenyon, has written approvingly of scientific creationism.
Pandas is published by the Haughton Publishing Company of Dallas, a publisher of agricultural books, but the copyright is held by the Foundation for Thought and Ethics (FTE) in Richardson, Texas. Although the FTE website scrupulously avoids mentioning religion, its articles of incorporation note with stark clarity that its "primary purpose is both religious and educational, which includes, but is not limited to, proclaiming, preaching, teaching, promoting, broadcasting, disseminating, and otherwise making known the Christian gospel and understanding of the Bible and the light it sheds on the academic and social issues of our day." In a fund-raising letter for the proposed third edition of Pandas, Jon Buell, president of the FTE, is equally frank about his goals:
We will energetically continue to publish and propel these strategic tools in the battle for the minds and hearts of the young.... Yes, most young Americans are exposed to numerous gospel presentations. But the fog of the alien world view deadens their responses. This is why we have to inundate them with a rational, defensible, well-argued Judeo-Christian world view. FTE's carefully-researched books do just that.
Charles Thaxton, the "academic editor" of Pandas , is the director of curriculum research for FTE and a fellow of the CSC. In a proto-ID book on the origin of life, Thaxton argued that "Special Creation by a Creator beyond the cosmos is a plausible view of origin science."
Given Pandas' pedigree and the affiliations of its authors, it is not surprising that the book is nothing more than disguised creationism. What is surprising is the transparency of this disguise. Despite the efforts of IDers to come up with new anti-Darwinian arguments, Pandas turns out to be nothing more than recycled scientific creationism, with most of the old arguments buffed up and proffered as new. (Unlike scientific creationism, however, Pandas adopts a studied neutrality toward the facts of astronomy and geology, instead of denying them outright.)
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Pandas' discussion of the Earth's age is a prime example of the book's creationist roots, and of its anti-scientific attitude. If the Earth were young ó say, the 6,000 to 10,000 years old posited by "young earth" biblical creationists ó then evolution would be false. Life simply could not have originated, evolved, and diversified in such a short time. But we now know from several independent and mutually corroborating lines of evidence that the Earth is 4.6 billion years old. All geologists agree on this. So what is Pandas' stance on this critical issue? The book merely notes that design proponents "are divided on the issue of the earth's age. Some take the view that the earth's history can be compressed into a framework of thousands of years, while others adhere to the standard old earth chronology." Well, what's the truth? This equivocation is an attempt to paper over a strong disagreement between young-earth creationists and old-earth creationists, both of whom have marched under the banner of ID. It is typical of creationists to exploit disagreements between evolutionists as proof that neo-Darwinism is dead while at the same time hiding their own disagreements from the public.
This equivocation about the fundamental fact of Earth's age does not bode well for the textbook's treatment of the fossil record. Indeed, in this area the authors continue their misrepresentations. Their basic premise is the old creationist argument that organisms appeared simultaneously and have remained largely unchanged ever since. Pandas says of the fossil record that "fully formed organisms appear all at once, separated by distinct gaps." That's not exactly true. Different types of organisms appear in a distinct sequence supporting evolution. The first fossils of living organisms, bacteria, appear 3.5 billion years ago, followed two billion years later by algae, the first organisms having true cells with a nucleus containing distinct chromosomes. Then, 600 million years ago, we see the appearance of rudimentary animals with shells, and many soft-bodied marine organisms. Later, in the Cambrian period, about 543 million years ago, a number of groups arose in a relatively short period of time, the so-called "Cambrian explosion." ("Short period" here means geologically short, in this case 10 million to 30 million years). The Cambrian groups include mollusks, starfish, arthropods, worms, and chordates (including vertebrates). And in some cases, such as worms, modern groups do not just spring into being, but increase in complexity over millions of years.
Creationists have always made much of the "Cambrian explosion," and IDers are no exception. The relatively sudden appearance of many groups seems to support the Genesis view of creation. But IDers — and Pandas — fail to emphasize several facts. First, the Cambrian explosion was not "sudden"; it took many millions of years. (We still do not understand why many groups originated in even this relatively short time, although it may reflect an artifact: the evolution of easily fossilized hard parts suddenly made organisms capable of being fossilized.) Moreover, the species of the Cambrian are no longer with us, though their descendants are. But over time, nearly every species that ever lived (more than 99 percent of them) has gone extinct without leaving descendants. Finally, many animals and plants do not show up as fossils until well after the Cambrian explosion: bony fishes and land plants first appeared around 440 million years ago, reptiles around 350 million years ago, mammals around 250 million years ago, flowering plants around 210 million years ago, and human ancestors around 5 million years ago. The staggered appearance of groups that become very different over the next 500 million years gives no support to the notion of instantaneously created species that thereafter remain largely unchanged. If this record does reflect the exertions of an intelligent designer, he was apparently dissatisfied with nearly all of his creations, repeatedly destroying them and creating a new set of species that just happened to resemble descendants of those that he had destroyed.
Pandas also makes much of the supposed absence of transitional forms: the "missing" links between major forms of life that, according to evolutionary theory, must have existed as common ancestors. Their absence, claim creationists, is a major embarrassment for evolutionary biology. Phillip Johnson's influential book Darwin on Trial, which appeared in 1993, particularly emphasizes these gaps, which, IDers believe, reflect the designer's creation of major forms ex nihilo. And there are indeed some animals, such as bats, that appear in the fossil record suddenly, without obvious ancestors. Yet in most cases these gaps are certainly due to the imperfection of the fossil record. (Most organisms do not get buried in aquatic sediments, which is a prerequisite for fossilization.) And species that are soft-bodied or have fragile bones, such as bats, degrade before they can fossilize. Paleontologists estimate that we have fossils representing only about one in a thousand of all the species that ever lived.
In its treatment of evolutionary transitions, Pandas is again guilty of distortion. Paleontologists have uncovered many transitional forms between major groups, almost more than we have a right to expect. Pandas simply ignores ó or waves away ó these "non-missing links," stating that "we cannot form a smooth, unambiguous transitional series linking, let's say, the first small horse to today's horse, fishes to amphibians, or reptiles to mammals." This is flatly wrong. All three cited transitions (and others) are well documented with fossils. Moreover, the transitional forms appear at exactly the right time in the fossil record: after the ancestral forms already existed, but before the "linked" later group had evolved.
Take one example: the link between early reptiles and later mammals, the so-called mammal-like reptiles. Three hundred fifty million years ago, the world was full of reptiles, but there were no mammals. By 250 million years ago, mammals had appeared on the scene. (Fossil reptiles are easily distinguished from fossil mammals by a complex of skeletal traits including features of the teeth and skull.) Around 275 million years ago, forms appear that are intermediate in skeletal traits between reptiles and mammals, in some cases so intermediate that the animals cannot be unambiguously classified as either reptiles or mammals. These mammal-like reptiles, which become less reptilian and more mammalian with time, are the no-longer-missing links between the two forms, important not only because they have the traits of both forms, but also because they occur at exactly the right time.
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One of these traits is worth examining in detail because it is among the finest examples of an evolutionary transition. This trait is the "chewing" hinge where the jaw meets the skull. In early reptiles (and their modern reptilian descendants), the lower jaw comprises several bones, and the hinge is formed by the quadrate bone of the skull and the articular bone of the jaw. As mammal-like reptiles become more mammalian, these hinge bones become smaller, and ultimately the jaw hinge shifts to a different pair of bones: the dentary (our "jawbone") and the squamosal, another bone of the skull. (The quadrate and articular, much reduced, moved into the middle ear of mammals, forming two of the bones that transmit sounds from the eardrum to the middle ear.) The dentary-squamosal articulation occurs in all modern mammals, the quadrate-articular in modern reptiles; and this difference is often used as the defining feature of these groups.
Like earlier creationist tracts, Pandas simply denies that this evolution of the jaw hinge occurred. It asserts that "there is no fossil record of such an amazing process," and further notes that such a migration would be "extraordinary." This echoes the old creationist argument that an adaptive transition from one type of hinge to another by means of natural selection would be impossible: members of a species could not eat during the evolutionary period when their jaws were being unhinged and then rehinged. (The implication is that the intelligent designer must have done this job instantaneously and miraculously.) But we have long known how this transition happened. It was easily accomplished by natural selection. In 1958, Alfred Crompton described the critical fossil: the mammal-like reptile Diarthrognathus broomi. D. broomi has, in fact, a double jaw joint with two hinges ó the reptilian one and the mammalian one! Obviously, this animal could chew. What better "missing link" could we find?
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It should embarrass IDers that so many of the missing links cited by Pandas as evidence for supernatural intervention are no longer missing. Creationists make a serious mistake when using the absence of transitional forms as evidence for an intelligent designer. In the last decade, paleontologists have uncovered a fairly complete evolutionary series of whales, beginning with fully terrestrial animals that became more and more aquatic over time, with their front limbs evolving into flippers and their hind limbs and pelvis gradually reduced to tiny vestiges. When such fossils are found, as they often are, creationists must then punt and change their emphasis to other missing links, continually retreating before the advance of science.
As for other transitional forms, IDers simply dismiss them as aberrant fossils. Pandas characterizes Homo erectus and other probable human ancestors as "little more than apes." But this is false. While H. erectus has a skull with large brow ridges and a braincase much smaller than ours, the rest of its skeleton is nearly identical to that of modern humans.The famous fossil Archaeopteryx, a small dinosaur-like creature with teeth and a basically reptilian skeleton but also with wings and feathers, is probably on or closely related to the line of dinosaurs that evolved into birds. But Pandas dismisses this fossil as just an "odd-ball" type, and laments instead the lack of the unfossilizable: "If only we could find a fossil showing scales developing the properties of feathers, or lungs that were intermediate between the very different reptilian and avian lungs, then we would have more to go on." It is again a typical creationist strategy that when skeletons of missing links turn up, creationists ignore them and insist that evidence of intermediacy be sought instead in the soft parts that rarely fossilize. In sum, the treatment of the fossil evidence for evolution in Pandas is shoddy and deceptive, and offers no advance over the discredited arguments of scientific creationism.
In contrast to its long treatment and dismissal of the fossil record, Pandas barely deals with evidence for evolution from development and vestigial traits. The best it can do is note that vestigial features can have a function, and therefore are not really vestigial. The vestigial pelvic bones and legs of the transitional whale Basilosaurus, which were not connected to the skeleton, may have functioned as a guide for the penis during mating. Such a use, according to the authors of Pandas , means that the legs and pelvis "were not vestigial as originally thought." But this argument is wrong: no evolutionist denies that the remnants of ancestral traits can retain some functionality or be co-opted for other uses. The "penis guide" has every bone in the mammalian pelvis and rear leg in reduced form ó femur, tibia, fibula, and digits. In Basilosaurus, nearly all of these structures lay within the body wall, and most parts were immobile. Apparently the intelligent designer had a whimsical streak, choosing to construct a sex aid that looked exactly like a degenerate pelvis and set of hind limbs.
And what about the strong evidence for evolution from biogeography? About this Pandas , like all creationist books, says nothing. The omission is strategic. It would be very hard for IDers to give plausible reasons why an "intelligent" designer stocked oceanic islands with only a few types of animals and plants ó and just those types with the ability to disperse from the nearest mainland. Biogeography has always been the Achilles' heel of creationists, so they just ignore it.
IV.
Although intelligent design rejects much of the evidence for evolution, it still admits that some evolutionary change occurs through natural selection. This change is what Pandas calls "microevolution," or "small scale genetic changes, observable in organisms." Such microevolutionary changes include the evolution of antibiotic resistance in bacteria, changes in the proportion of different-colored moths due to predation by birds, and all changes wrought by artificial selection. But Pandas hastens to add that microevolution gives no evidence for the origin of diverse types of organisms, because "these limited changes do not accumulate the way Darwinian evolutionary theory requires in order to produce macro changes. The process that produces macroevolutionary changes [defined here as "large scale changes, leading to new levels of complexity"] must be different from any that geneticists have studied so far."
So, though one can use selection to transform a wolf into either a Chihuahua or a St. Bernard, that is merely microevolution: they are all still dogs. And a DDT-resistant fly is still a fly. Pandas thus echoes the ID assertion that natural selection cannot do more than create microevolutionary changes: "It cannot produce new characteristics. It only acts on traits that already exist." But this is specious reasoning. As we have noted, fossils already show that "macro change," as defined by Pandas , has occurred in the fossil record (the evolution of fish into amphibians, and so on). And if breeders have not turned a dog into another kind of animal, it is because dog breeding has been going on for only a few thousand years, while the differences between dogs and cats, for example, have evolved over more than ten million years. No principle of evolution dictates that evolutionary changes observed during a human lifetime cannot be extrapolated to much longer periods.
In fact, Pandas admits that the fruit flies of Hawaii ó a diverse group of more than 300 species ó have all evolved from a common ancestor. We now know that this common ancestor lived about 20 million years ago. The species of Hawaiian flies differ in many traits, including size, shape, ecology, color pattern, mating behavior, and so on. One can in fact make a good case that some of the fly species differ more from each other than humans differ from chimps. Why, then, do IDers assert that chimps and humans (whose ancestor lived only 5 million years ago) must have resulted from separate acts of creation by the intelligent designer, while admitting that fruit flies evolved from a common ancestor that lived 20 million years ago? The answer is that humans must at all costs not be lumped in with other species, so as to protect the biblical status of humans as uniquely created in God's image.
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According to Pandas, the theory of "limits to evolution" is a scientific one: "The idea of intelligent design does not preclude the possibility that variation within species occurs, or that new species are formed from existing populations . . . the theory of intelligent design does suggest that there are limits to the amount of variation that natural selection and random change mechanisms can produce." But there is nothing in the theory of intelligent design that tells us how far evolution can go. This "thus far and no further" view of evolution comes not from any scientific findings of ID; it comes from ID's ancestor, scientific creationism. Scientific Creationism notes that "the creation model . . . recognizes only the kind as the basic created unit, in this case, mankind," and a chart contrasting evolution with the "creation model" says that the former predicts "new kinds appearing," while the latter says "no new kinds appearing."
But what is a "kind"? No creationist has ever defined it, though they are all very sure that humans and apes are different "kinds." In fact, the notion that evolution and creation have operated together, with the latter creating distinct "kinds," was nicely rebutted by Darwin in On the Origin of Species:
Several eminent naturalists . . . admit that they [evolved species] have been produced by variation, but they refuse to extend the same view to other and very slightly different forms. Nevertheless they do not pretend that they can define, or even conjecture, which are the created forms of life, and which are those produced by secondary laws. They admit variation as a vera causa in one case, they arbitrarily reject it in another, without assigning any distinction in the two cases. The day will come when this will be given as a curious illustration of the blindness of preconceived opinion. These authors seem no more startled at a miraculous act of creation than at an ordinary birth. But do they really believe that at innumerable periods in the earth's history certain elemental atoms have been commanded suddenly to flash into living tissues? Do they believe that at each supposed act of creation one individual or many were produced? Were all the infinitely numerous kinds of animals and plants created as egg or seed, or as full grown? and in the case of mammals, were they created bearing the false marks of nourishment from the mother's womb? Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence.
In fact, the biblical appendix of Scientific Creationism shows that the term "kind" derives from the biblical notion of created kinds:
The Scriptures are very clear in their teaching that God created all things as He wanted them to be, each with its own particular structure, according to His own sovereign purposes. The account of Genesis 1, for example, indicates that at least ten major categories of organic life were specially created "after his kind." . . . Finally, man "kind" was created as another completely separate category. The phrase "after his kind" occurs ten times in this first chapter of Genesis.
There is thus a clear line of descent from the story of Genesis to the ID notion of evolutionary limits, a line charted by what Darwin called "the blindness of preconceived opinion." Until IDers tell us what the limits to evolution are, how they can be ascertained, and what evidence supports these limits, this notion cannot be regarded as a genuinely scientific claim.
V.
IDers make one claim that they tout as truly novel, a claim that has become quite popular. It is the idea that organisms show some adaptations that could not be built by natural selection, thus implying the need for a supernatural creative force such as an intelligent designer. These adaptations share a property called "irreducible complexity," a characteristic discussed in Pandas but defined more explicitly by Michael Behe in 1996 in his book Darwin's Black Box: The Biochemical Challenge to Evolution: "By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning."
Many man-made objects show this property: Behe cites the mousetrap, which would not work if even one part were removed, such as the catch, the spring, the base, and so on. Pandas mentions a car engine, which will not work if one removes the fan belt, spark plugs, distributor cap, or any of numerous individual parts. A famous example of an irreducibly complex system in the biological realm is the "camera" eye of humans and other vertebrates. The eye has many parts whose individual removal would render the organ useless, including the lens, retina, and optic nerve.
The reason IDers love "irreducibly complex" features of organisms is that natural selection is powerless (or so they claim) to create such features. As Behe notes:
An irreducibly complex system cannot be produced directly ... by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional.... Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.
"One fell swoop," of course, implies that the feature must have been produced by the miraculous intervention of the intelligent designer.
But this argument for intelligent design has a fatal flaw. We have realized for decades that natural selection can indeed produce systems that, over time, become integrated to the point where they appear to be irreducibly complex. But these features do not evolve by the sequential addition of parts to a feature that becomes functional only at the end. They evolve by adding, via natural selection, more and more parts into an originally rudimentary but functional system, with these parts sometimes co-opted from other structures. Every step of this process improves the organism's survival, and so is evolutionarily possible via natural selection.
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Consider the eye. Creationists have long maintained that it could not have resulted from natural selection, citing a sentence from On the Origin of Species: "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." But in the next passage, invariably omitted by creationists, Darwin ingeniously answers his own objection:
Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory.
Thus our eyes did not suddenly appear as full-fledged camera eyes, but evolved from simpler eyes, having fewer components, in ancestral species. Darwin brilliantly addressed this argument by surveying existing species to see if one could find functional but less complex eyes that not only were useful, but also could be strung together into a hypothetical sequence showing how a camera eye might evolve. If this could be done ó and it can ó then the argument for irreducible complexity vanishes, for the eyes of existing species are obviously useful, and each step in the hypothetical sequence could thus evolve by natural selection.
A possible sequence of such changes begins with pigmented eye spots (as seen in flatworms), followed by an invagination of the skin to form a cup protecting the eyespot and allowing it to better localize the image (as in limpets), followed by a further narrowing of the cup's opening to produce an improved image (the nautilus), followed by the evolution of a protective transparent cover to protect the opening (ragworms), followed by coagulation of part of the fluid in the eyeball into a lens to help focus the light (abalones), followed by the co-opting of nearby muscles to move the lens and vary the focus (mammals). The evolution of a retina, an optic nerve, and so on would follow by natural selection. Each step of this transitional "series" confers increased adaptation on its possessor, because it enables the animal to gather more light or to form better images, both of which aid survival. And each step of this process is exemplified by the eye of a different living species. At the end of the sequence we have the camera eye, which seems irreducibly complex. But the complexity is reducible to a series of small, adaptive steps.
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Now, we do not know the precise order in which the components of the camera eye evolved ó but the point is that the appearance of "irreducible complexity" cannot be an argument against neo-Darwinism if we can document a plausible sequence in which the complexity can arise from a series of adaptive steps. The "irreducible complexity" argument is not, in fact, completely novel. It descends, with modification, from the British theologian William Paley, who in 1802 raised the famous "argument from design" in his book Natural Theology. Paley argued that just as finding a watch on the ground implies a conscious designer (the watchmaker), so finding an equally complex organism implies a cosmic designer (God).
But the eye is not a watch. The human eye, though eminently functional, is imperfect ó certainly not the sort of eye an engineer would create from scratch. Its imperfection arises precisely because our eye evolved using whatever components were at hand, or produced by mutation. Since our retina evolved from an everted part of the brain, for example, the nerves and blood vessels that attach to our photoreceptor cells are on the inside rather than the outside of the eye, running over the surface of the retina. Leakage of these blood vessels can occlude vision, a problem that would not occur if the vessels fed the retina from behind. Likewise, to get the nerve impulses from the photocells to the brain, the different nerves must join together and dive back through the eye, forming the optic nerve. This hole in the retina creates a blind spot in the eye, a flaw that again would be avoidable with a priori design. The whole system is like a car in which all the wires to the dashboard hang inside the driver's compartment instead of being tucked safely out of sight. Evolution differs from a priori design because it is constrained to operate by modifying whatever features have evolved previously. Thus evolution yields fitter types that often have flaws. These flaws violate reasonable principles of intelligent design.
IDers tend to concentrate more on biochemistry than on organs such as the eye, citing "irreducibly complex" molecular systems such as the mechanism for blood-clotting and the immune system. Like the eye, these systems supposedly could not have evolved, since removal of any step in these pathways would render the entire pathway non-functional. (This biochemical complexity is the subject of Behe's book Darwin's Black Box.) Discussing the blood-clotting system in its sixth chapter (partially written by Behe), Pandas asserts that "like a car engine, biological systems can only work after they have been assembled by someone who knows what the final result will be." This is nonsense. As we have seen in the case of the eye, biological systems are not useful only at the end of a long evolutionary process, but during every step of that process. And biochemical systems ó like all adaptations created by natural selection ó are not assembled with foresight. Whatever useful mutations happen to arise get folded into the system.
There is no doubt that many biochemical systems are dauntingly complex. A diagram of the blood-clotting pathway looks like a complicated circuit board, with dozens of proteins interacting with one another to one end: healing a wound. And the system seems irreducibly complex, because without any of several key proteins, the blood would not clot. Yet such biochemical systems evolved in the same way that the eye evolved, by adding parts successively and adaptively to simpler, functioning systems. It is more difficult to trace the evolution of biochemical pathways than of anatomical structures because the ancestral metabolic pathways are no longer present. But biologists are beginning to provide plausible scenarios for how "irreducibly complex" biochemical pathways might have evolved. As expected, these systems involve using bits co-opted from other pathways originally having different functions. (Thus, one of the enzymes in the blood-clotting system also plays a role in digestion and cell division.) In view of our progress in understanding biochemical evolution, it is simply irrational to say that because we do not completely understand how biochemical pathways evolved, we should give up trying and invoke the intelligent designer. If the history of science shows us anything, it is that we get nowhere by labeling our ignorance "God."
VI.
Insofar as intelligent-design theory can be tested scientifically, it has been falsified. Organisms simply do not look as if they had been intelligently designed. Would an intelligent designer create millions of species and then make them go extinct, only to replace them with other species, repeating this process over and over again? Would an intelligent designer produce animals having a mixture of mammalian and reptilian traits, at exactly the time when reptiles are thought to have been evolving into mammals? Why did the designer give tiny, non-functional wings to kiwi birds? Or useless eyes to cave animals? Or a transitory coat of hair to a human fetus? Or an appendix, an injurious organ that just happens to resemble a vestigial version of a digestive pouch in related organisms? Why would the designer give us a pathway for making vitamin C, but then destroy it by disabling one of its enzymes? Why didn't the intelligent designer stock oceanic islands with reptiles, mammals, amphibians, and freshwater fish, despite the suitability of such islands for these species? And why would he make the flora and fauna on those islands resemble that of the nearest mainland, even when the environments are very different? Why, about a million years ago, would the designer produce creatures that have an apelike cranium perched atop a humanlike skeleton? And why would he then successively replace these creatures with others having an ever-closer resemblance to modern humans?
There are only two answers to these questions: either life resulted not from intelligent design, but from evolution; or the intelligent designer is a cosmic prankster who designed everything to make it look as though it had evolved. Few people, religious or otherwise, will find the second alternative palatable. It is the modern version of the old argument that God put fossils in the rocks to test our faith.
The final blow to the claim that intelligent design is scientific is its proponents' admission that we cannot understand the designer's goals or methods. Behe owns up to this in Darwin's Black Box: "Features that strike us as odd in a design might have been placed there by the designer for a reason ó for artistic reasons, to show off, for some as-yetundetectable practical purpose, or for some unguessable reason ó or they might not." And, discussing skeletal differences between placental and marsupial mammals, Pandas notes:
Why were not the North American placentals given the same bones? Would an intelligent designer withhold these structures from placentals if they were superior to the placental system? At present we do not know; however, we all recognize that an engineer can choose any of several different engineering solutions to overcome a single design problem. An intelligent designer might reasonably be expected to use a variety (if a limited variety) of design approaches to produce a single engineering solution, also. Even if it is assumed that an intelligent designer did indeed have a good reason for every decision that was made, and for including every trait in each organism, it does not follow that such reasons will be obvious to us.
Well, if we admit that the designer had a number of means and motives, which can be self-contradictory, arbitrary, improvisatory, and "unguessable," then we are left with a theory that cannot be rejected. Every conceivable observation of nature, including those that support evolution, becomes compatible with ID, for the ways of the designer are unfathomable. And a theory that cannot be rejected is not a scientific theory. If IDers want to have a genuinely scientific theory, let them propose a model that can be rigorously tested.
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Given its lack of rigor, one might expect that ID theory would not inspire much scientific research. And there is virtually none. Despite the claims of ID to be a program of research, its adherents have published only one refereed paper supporting ID in a scientific journal: a review of ID by Stephen C. Meyer, the director of the Discovery Institute's Center for Science and Culture, which appeared in the Proceedings of the Biological Society of Washington. This paper merely rehashes ID arguments for why natural selection and evolution cannot explain the diversity of life and then asserts that intelligent design is the only alternative. It distorts the evolutionary literature it purports to review, and it neither advances new scientific arguments nor suggests any way that ID better explains patterns in nature. Not surprisingly, the Council of the Biological Society of Washington later disowned the paper because it did "not meet the scientific standards of the Proceedings."
The gold standard for modern scientific achievement is the publication of new results in a peer-reviewed scientific journal. By that standard, IDers have failed miserably. As William Dembski himself noted, "There are good and bad reasons to be skeptical of intelligent design. Perhaps the best reason is that intelligent design has yet to establish itself as a thriving scientific research program." IDers desperately crave scientific respectability, but it is their own theory that prevents them from attaining it. Thus, while IDers demand that evolutionists produce thousands of transitional fossils and hundreds of detailed scenarios about the evolution of biochemical pathways, they put forth no observations supporting the plausibility of a supernatural designer, nor do they show how appeal to such a designer could explain the fossil record, embryology, and biogeography better than neo-Darwinism. Herbert Spencer could have been describing ID when he declared that "those who cavalierly reject the Theory of Evolution as not being adequately supported by facts, seem to forget that their own theory is supported by no facts at all. Like the majority of men who are born to a given belief, they demand the most rigorous proof of any adverse belief, but assume that their own needs none."
Finally, the reliance of ID on supernatural intervention means that the enterprise cannot be seen, strictly speaking, as scientific. In his rejection of scientific creationism in McLean v. Arkansas, Judge Overton described the characteristics of good science:
(1) It is guided by natural law;
(2) It has to be explanatory by reference to natural law;
(3) It is testable against the empirical world;
(4) Its conclusions are tentative, i.e., are not necessarily the final word; and
(5) It is falsifiable.
By invoking the repeated occurrence of supernatural intervention by an intelligent designer to create new species and new traits, ID violates criteria 1 and 2; and in its ultimate reliance on Christian dogma and God, it violates criteria 3, 4, and 5.
In candid moments, usually when writing for or speaking to a religious audience, IDers admit the existence not only of supernatural acts as a part of their theory, but also of Christian supernatural acts. In a foreword to a book on creationism, Johnson wrote: "The intelligent design movement starts with the recognition that 'In the beginning was the Word,' and 'In the beginning God created.' Establishing that point isn't enough, but it is absolutely essential to the rest of the gospel message." And here is Dembski writing in Touchstone, a Christian magazine: "The world is a mirror representing the divine life.... Intelligent design readily embraces the sacramental nature of physical reality. Indeed intelligent design is just the Logos theology of John's Gospel restated in the idiom of information theory." Indeed, in the manuscript draft of the first edition of Pandas , the terms "creationism," "creationist," and "creation" are used repeatedly instead of the equivalent ID terms, and "creationism" is defined identically to "intelligent design" in the published version. Nothing gives a clearer indication that one ancestor of this textbook was the Bible.
It is clear, then, that intelligent design did not arise because of some long-standing problems with evolutionary theory, or because new facts have called neoDarwinism into question. ID is here for only one reason ó to act as a Trojan horse poised before the public schools: a seemingly secular vessel ready to inject its religious message into the science curriculum. The contents of Pandas , and of the other writings of IDers, are simply a cunning pedagogical ploy to circumvent legal restrictions against religious creationism. (With any luck, though, the publicity will backfire. Last month The York Dispatch in Pennsylvania reported that the Foundation for Thought and Ethics, the group that publishes this textbook and others designed to present "a Christian perspective," wanted to intervene in the Dover lawsuit. According to John Buell, the foundation's president, the association of ID with creationism "would make the book radioactive," and his outfit could lose as much as $525,000 in sales.)
ID is part of what Johnson candidly calls the "wedge strategy," a carefully crafted scheme that begins with the adoption of intelligent design as an alternative theory to evolution, after which ID will edge out evolution until it is the only view left, after which it will become full-blown biblical creationism. The ultimate goal is to replace naturalist science with spiritualist thinking, and the method is to hammer the wedge of ID into science at its most vulnerable point: public education. In Johnson's own words:
So the question is: "How to win?" That's when I began to develop what you now see full-fledged in the "wedge" strategy: "stick with the most important thing," the mechanism and the building up of information. Get the Bible and the Book of Genesis out of the debate because you do not want to raise the so-called Bible-science dichotomy. Phrase the argument in such a way that you can get it heard in the secular academy and in a way that tends to unify the religious dissenters. That means concentrating on, "Do you need a Creator to do the creating, or can nature do it on its own?" and refusing to get sidetracked onto other issues, which people are always trying to do.
Johnson was even more explicit in 1999 in remarks to a conference on "Reclaiming America for Christ." Rob Boston reported Johnson's remarks in Church & State magazine:
Johnson calls his movement "The Wedge." The objective, he said, is to convince people that Darwinism is inherently atheistic, thus shifting the debate from creationism v. evolution to the existence of God v. the nonexistence of God. From there people are introduced to "the truth" of the Bible and then "the question of sin" and finally "introduced to Jesus."
Other major figures in the ID movement have been equally clear about their religious motivations. Here is Dembski:
But there are deeper motivations. I think at a fundamental level, in terms of what drives me in this is that I think God's glory is being robbed by these naturalistic approaches to biological evolution, creation, the origin of the world, the origin of biological complexity and diversity. When you are attributing the wonders of nature to these mindless material mechanisms, God's glory is getting robbed.
And here is Jonathan Wells, a member of Reverend Moon's Unification Church:
Father's [Reverend Moon's] words, my studies, and my prayers convinced me that I should devote my life to destroying Darwinism, just as many of my fellow Unificationists had already devoted their lives to destroying Marxism. When Father chose me (along with about a dozen other seminary graduates) to enter a Ph.D. program in 1978, I welcomed the opportunity to prepare myself for battle.
Do these people really believe in intelligent design? There is no reason to think otherwise. They are not lying for their cause, but sincerely hold that life on earth reflects a succession of miracles worked by a supernatural agent. In fact, they view evolutionists as the duplicitous ones. In an interview in The Sacramento Bee in 1991, Johnson proclaimed that "scientists have long known that Darwinism is false. They have adhered to the myth out of self-interest and a zealous desire to put down God." Never mind that many scientists, including evolutionists, are religious.
Given the overwhelming evidence for evolution and the lack of evidence for ID, how can intelligent people hold such views? Is their faith so strong that it blinds them to all evidence? It is a bit more complicated than that. After all, many theologians and religious people accept evolution. The real issues behind intelligent design ó and much of creationism ó are purpose and morality: specifically, the fear that if evolution is true, then we are no different from other animals, not the special objects of God's creation but a contingent product of natural selection, and so we lack real purpose, and our morality is just the law of the jungle. Tom DeLay furnished a colorful example of this view on the floor of the House of Representatives on June 16, 1999. Explaining the causes of the massacre at Columbine High School, he read a sarcastic letter in a Texas newspaper that suggested that "it couldn't have been because our school systems teach the children that they are nothing but glorified apes who have evolutionized out of some primordial soup of mud."
The notion that naturalism and materialism are the enemies of morality and a sense of human purpose, and that religion is their only ally, is pervasive in the writings of IDers. As Johnson noted, "Once God is culturally determined to be imaginary, then God's morality loses its foundation and withers away." Nancy Pearcey, a senior fellow of the Discovery Institute's Center for Science and Culture, summarizes why evolution disturbs so many Americans:
Why does the public care so passionately about a theory of biology? Because people sense intuitively that there's much more at stake than a scientific theory. They know that when naturalistic evolution is taught in the science classroom, then a naturalistic view of ethics will be taught down the hallway in the history classroom, the sociology classroom, the family life classroom, and in all areas of the curriculum.
Even some parents in Dover, though opposed to teaching ID in school, worry that learning evolution will erode the Christian values that they are trying to instill in their children.
But the acceptance of evolution need not efface morality or purpose. Evolution is simply a theory about the process and patterns of life's diversification, not a grand philosophical scheme about the meaning of life. Philosophers have argued for years about whether ethics should have a basis in nature. There is certainly no logical connection between evolution and immorality. Nor is there a causal connection: in Europe, religion is far less pervasive than in America, and belief in evolution is more widespread, but somehow the continent remains civilized. Most religious scientists, laymen, and theologians have not found the acceptance of evolution to impede living an upright, meaningful life. And the idea that religion provides the sole foundation for meaning and morality also cannot be right: the world is full of skeptics, agnostics, and atheists who live good and meaningful lives.
Barring a miracle, the Dover Area School District will lose its case. Anyone who bothers to study ID and its evolution from earlier and more overtly religious forms of creationism will find it an unscientific, faith-based theory ultimately resting on the doctrines of fundamentalist Christianity. Its presentation in schools thus violates both the Constitution and the principles of good education. There is no secular reason why evolutionary biology, among all the sciences, should be singled out for a school-mandated disclaimer. But the real losers will be the people of Dover, who will likely be saddled with huge legal bills and either a substantial cut in the school budget or a substantial hike in property taxes. We can also expect that, if they lose, the IDers will re-group and return in a new disguise even less obviously religious. I await the formation of the Right to Teach Problems with Evolution Movement.
IDers have been helped by Americans' continuing doubts about the truth of evolution. According to a Gallup poll taken last year, 45 percent of Americans agree with the statement, "God created human beings pretty much in their present form at one time within the last 10,000 years." Asked if evolution is well supported by evidence, 35 percent of Americans said yes, 35 percent said no, and 29 percent said they lack the knowledge to reply. As a rationalist, I cannot help but believe that the first group would swell were Americans to be thoroughly taught the evidence for evolution, which is rarely done in public high schools. I have seen creationist students become evolutionists when they learn about biogeography or examine the skulls of mammal-like reptiles. What we need in the schools is not less teaching of evolution but more.
In the end, many Americans may still reject evolution, finding the creationist alternative psychologically more comfortable. But emotion should be distinguished from thought, and a "comfort level" should not affect what is taught in the science classroom. As Judge Overton wrote in his magisterial decision striking down Arkansas Act 590, which mandated equal classroom time for "scientific creationism":
The application and content of First Amendment principles are not determined by public opinion polls or by a majority vote. Whether the proponents of Act 590 constitute the majority or the minority is quite irrelevant under a constitutional system of government. No group, no matter how large or small, may use the organs of government, of which the public schools are the most conspicuous and influential, to foist its religious beliefs on others.
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