William A. Dembski
Conceptual Foundations of Science
Waco, Texas 76798
Talk presented at the annual American Academy of Religion meeting,
San Antonio, November 22, 2004
According to evolutionist Francisco Ayala, Darwin’s greatest achievement was to show that the organized complexity of living things could be brought about without recourse to a designing intelligence. Given this view of Darwin’s achievement, what evolutionary biology has come to mean by “evolution” is an unintelligent or blind form of it. This was brought home to me two years ago at a debate in which I participated. I was invited, along with my colleague and friend Michael Behe, to debate Darwinists Kenneth Miller and Robert Pennock at the American Museum of Natural History in Manhattan. The debate was initially titled “Blind Evolution or Intelligent Design?” Yet, when the debate actually took place on April 23, 2002, the program bulletin distributed at the event quietly dropped the word “blind” and titled the debate simply “Evolution or Intelligent Design?” The original title was more accurate. Intelligent design, the view for which Behe and I were arguing, is opposed to blind evolution, not to evolution simpliciter.
Why should anyone doubt blind evolution or, as it is now increasingly being called, unintelligent evolution? At the heart of unintelligent evolution is Darwin’s theory. It is no accident that in debates over biological evolution Darwin’s name keeps coming up. Nor are repeated references to Darwin and Darwinism simply out of respect for the history of the subject, as though evolutionary biology needed constantly to be reminded of its founder. Darwin looms larger than life in the study of biological origins because his theory constitutes the very bedrock of evolutionary biology. Indeed, nothing in evolutionary biology makes sense apart from Darwinism.
To see this, we need to understand Darwinism’s role in contemporary evolutionary theory. Darwinism is really two claims. The less crucial claim is that all organisms trace their lineage back to a universal common ancestor. Thus you, the fly buzzing around your head, and the bacteria perched on the fly all share the same great-great-great grandparent. Alternatively, any two organisms are n-th cousins k-times removed where n and k depend on the two organisms in question. This claim is referred to as “common descent” or “universal common ancestry.” Although evolutionary biology is committed to common descent, that is not its central claim.
The central claim of evolutionary biology, rather, is that an unintelligent physical process can account for the emergence of all biological complexity and diversity. Filling in the details of that process remains a matter for debate among evolutionary biologists. Yet it is an in-house debate, and one essentially about details. In broad strokes, however, any unguided physical process capable of producing biological complexity must have three components: (1) hereditary transmission, (2) incidental change, and (3) natural selection.
Think of it this way: Start with some organism. It incurs some change. The change is incidental in the sense that it doesn’t anticipate future changes that subsequent generations of organisms may experience (neo-Darwinism, for instance, treats such changes as random mutations or errors in genetic material). What’s more, incidental change is heritable and therefore can be transmitted to the next generation. Whether it actually is transmitted to the next generation and then preferentially preserved in subsequent generations, however, depends on whether the change is in some sense beneficial to the organism. If so, then natural selection will be likely to preserve organisms exhibiting that change.
This picture is perfectly general. As already noted, it can accommodate neo-Darwinism. It can also accommodate Lamarckian evolution, whose incidental changes occur as organisms, simply by putting to use existing structures, enhance or modify the functionalities of those structures. It can accommodate Lynn Margulis’s idea of symbiogenetic evolution, whose incidental changes occur as different types of organisms come together to form a new, hybrid organism. Other forms of incidental change that it can accommodate include genetic drift, lateral gene transfer, and the action of regulatory genes in development.
Evolutionary biologists debate the precise role and extent of hereditary transmission and incidental change. The debate can even be quite sharp at times. But evolutionary biology leaves unchallenged Darwinism’s holy of holies—natural selection. Darwin himself was unclear about the mechanisms of hereditary transmission and incidental change. But whatever form they took, Darwin was convinced that natural selection was the key to harnessing them. The same is true for contemporary evolutionary biologists. That’s why to this day we hear repeated references to Darwin’s theory of natural selection but not to Darwin’s theory of variation or Darwin’s theory of inheritance.
Apart from design or teleology, what can coordinate the incidental changes that hereditary transmission passes from one generation to the next? To perform such coordination, evolution requires a designer substitute. Darwin’s claim to fame was to propose natural selection as a designer substitute. But natural selection is no substitute for intelligent coordination. All natural selection does is narrow the variability of incidental change by weeding out the less fit. What’s more, it acts on the spur of the moment, based solely on what the environment at present deems fit, and thus without any foresight of future possibilities. And yet this unintelligent process, when coupled with another unintelligent process (incidental change), is supposed to produce designs that exceed the capacities of any designing intelligences in our experience.
Leaving aside small-scale evolutionary changes, like insects developing insecticide resistance (which no one disputes anyway), where is the evidence that natural selection can accomplish the intricacies of bioengineering that are manifest throughout the living world (like producing insects in the first place)? Where is the evidence that the sorts of incidental changes required for large-scale evolution ever occur? The evidence simply isn’t there. But don’t take my word for it. Three years ago, cell biologist Franklin Harold published a book with Oxford University Press titled The Way of the Cell. In it he explicitly repudiated intelligent design: “We should reject, as a matter of principle, the substitution of intelligent design for the dialogue of chance and necessity.” (Note that the dialogue between chance and necessity here refers to the interplay of incidental change and natural selection, in other words, unintelligent evolution.) And yet, Harold continued, “But we must concede that there are presently no detailed Darwinian accounts of the evolution of any biochemical or cellular system, only a variety of wishful speculations.”
James Shapiro, Stuart Kauffman, and Lynn Margulis have raised similar doubts. But what are their alternatives? Certainly not intelligent design. Shapiro places his hopes in what he calls “natural genetic engineering”; in other words, organisms design themselves. But Shapiro has no account of how organisms of sufficient complexity can arise in the first place to do their own genetic engineering. As for Kauffman, he places his hopes in laws of self-organization and complexity. Yet a decade after he published At Home in the Universe: The Search for Laws of Self-Organization and Complexity (publication date 1995), Kauffman is still searching for those laws. And as for Lynn Margulis, she places her hopes in symbiogenesis, where the driving force behind evolution becomes organisms coming together to hybridize and thereby increase biological complexity. Though Margulis has argued effectively that symbiogenesis plays some role in biological evolution, she is far from showing that it is the missing key. In short, the proposals on the table for shoring up Darwinian theory with still other blind material mechanisms are even more speculative than what they are trying to shore up.
To appreciate what’s at stake in raising criticisms and doubts about unintelligent evolution, imagine what would happen to the germ theory of disease if scientists never found any microorganisms or viruses that produced diseases. That’s the problem with unintelligent evolution. To be sure, evolutionary theorists have proposed mechanisms to explain small-scale changes in organisms (like bacteria developing antibiotic resistance). What they have not shown, however, is how such mechanisms can reasonably be extrapolated to explaining large-scale changes in organisms (like bacteria developing the complex molecular machines that Michael Behe discusses in his book Darwin’s Black Box). In place of detailed, testable accounts of how a complex biological system could realistically have emerged, evolutionary theory offers handwaving just-so stories for how such systems might have emerged in some idealized conceptual space far removed from biological reality.
This is bad enough, but the situation is even worse for evolutionary theory. It’s one thing, as I have been doing, to suggest that unintelligent evolution has yet to be adequately substantiated. Proponents of unintelligent evolution can then just claim that more effort and research funds will vindicate the theory. But I want to press the critique further. In particular, I want to argue that evolutionary theory, by being wedded exclusively to unintelligent material forces, lacks the conceptual resources to explain biological complexity and diversity.
One way to see this is by reflecting on a principle of scientific reasoning described by John Stuart Mill, a contemporary of Darwin’s. In his System of Logic, Mill put forward his well-known method of difference. According to the method of difference, to explain a difference in effects, one must identify a difference in causes. Put differently, common causes cannot explain differences in effects. To see the validity of this principle, consider the following difference in effects, namely, slowed reflexes versus ordinary reflexes, as well as the following possible causes, namely, watching television, combing hair, consuming alcohol, and eating candy. Watching television, combing hair, and eating candy are equally compatible with slowed as well as ordinary reflexes. Consuming alcohol, however, is not. Consuming alcohol is reliably correlated with slowed reflexes. It is the difference that makes a difference here.
Now, consider the following difference in effects directly relevant to our discussion, namely, increasing biological complexity in the history of life versus stagnating or even dwindling biological complexity over that same history. Evolutionary theory wants to say that what makes the difference in leading life to ever greater levels of biological complexity is systems that reproduce subject to the three factors described previously, namely, (1) hereditary transmission, (2) incidental change, and (3) natural selection. The problem is, however, that these three factors are not reliably correlated with increasing complexity of replicacting systems. There are many examples of this. Brian Goodwin, in How the Leopard Changed Its Spots, relates one notable instance:
In a classic experiment, [Sol] Spiegelman ... showed what happens to a molecular replicating system in a test tube, without any cellular organization around it. The replicating molecules (the nucleic acid templates) require an energy source, building blocks (i.e., nucleotide bases), and an enzyme to help the polymerization process that is involved in self-copying of the templates. Then away it goes, making more copies of the specific nucleotide sequences that define the initial templates. But the interesting result was that these initial templates did not stay the same; they were not accurately copied. They got shorter and shorter until they reached the minimal size compatible with the sequence retaining self-copying properties. And as they got shorter, the copying process went faster. So what happened with natural selection in a test tube: the shorter templates that copied themselves faster became more numerous, while the larger ones were gradually eliminated. This looks like Darwinian evolution in a test tube. But the interesting result was that this evolution went one way: toward greater simplicity. Actual evolution tends to go toward greater complexity, species becoming more elaborate in their structure and behavior, though the process can also go in reverse, toward simplicity. But DNA on its own can go nowhere but toward greater simplicity. In order for the evolution of complexity to occur, DNA has to be within a cellular context; the whole system evolves as a reproducing unit.
But that raises the next question, which is how does evolution produce whole systems capable of providing the right context for evolution to thrive and thus bring about increasing complexity? Evolutionists have no answer here. But again, don’t take my word for it. According to Stuart Kauffman, one of the leading self-organizational theorists, “One of the deep puzzles is why the universe has become complex. Why has the biosphere become complex? Why has the number of ways of earning a living increased so dramatically? We have no theory about this overwhelming feature of our universe.” (www.iscid.org/stuartkauffman-chat.php)
Life over the course of natural history has become more complex. One of the great appeals of evolutionary theory, when thinkers such as Darwin first proposed it, was to underwrite a progressive, onward-and-upward, complexity-increasing form of evolution. And yet, on closer examination, it becomes evident that the theory lacks the conceptual resources to do so. To be sure, the unguided material mechanisms to which evolutionary theory appeals play a significant role in the history of life (natural selection certainly has played a role in preserving species and adapting them to their environments). But as Mill’s method of difference points up (especially when combined with experiments like Sol Spiegelman’s), these mechanisms, and any theory of unintelligent evolution based exclusively on them, cannot be the whole story. Simply put, evolutionary theory is incomplete. Moreover, the incompleteness here is a gaping conceptual lacuna, and not merely a pocket of ignorance that promises to be quickly remedied.
To appreciate the problem here, consider the following analogy. Imagine an immense stadium with a million people. Each person is initially standing and holds a coin. They now begin tossing their coins. Each person remains standing so long as he or she tosses heads, but must sit down otherwise. On average, at the end of twenty tosses one person will be left standing. The rationale here is this: after the first toss, on average 500,000 people will be left standing; after the second toss, on average half that number will be left standing, or 250,000; after the third toss, on average half that number will be left standing, or 125,000; and so on. Twenty tosses, on average, leaves one person standing.
Now, suppose after twenty tosses exactly one person is left standing. Do we turn to that person and ask, Hey, what’s your secret for coin tossing? Hardly. The theory of coin tossing (probability theory) tells us that out of a million such coin-tossers, one person will on average be left standing who has tossed twenty heads in a row. So too, the theory of evolution tells us that, periodically, nature will produce beneficial incidental changes that, rather than simply disappearing into the dust of prehistory, will be passed on by the power of natural selection. Through a long chain of such events, the cumulative effect of natural selection and incidental change over several billion years is likely to produce the degree of biological complexity and diversity we observe now. Just as the theory of coin tossing does not justify attributing to the person who tossed twenty heads in a row any special skill or wisdom at coin tossing, so too the theory of evolution does not justify attributing to the evolutionary process any special skill or wisdom at generating biological complexity and diversity. In each case, the outcome is properly regarded as the expected or predictable outcome of unintelligent material mechanisms and not as the creative achievement of a designing intelligence.
But there is a crucial difference between these two cases. In the coin tossing case, we have the observed outcome (twenty heads in a row) as well as a detailed history and mechanistic theory to account for the outcome. In the history of life, by contrast, we have only the observed outcome (the multiplicity of complex life forms, both extant and fossilized) but neither a detailed history nor a mechanistic theory that adequately accounts for this outcome. The key point to note here is the presence of an adequate mechanistic theory in one case, but its absence in the other. In the coin tossing case, give a million people each a coin, let them start tossing, and after twenty tosses one person will usually be left standing. By contrast, let some bacteria evolve within the perimeters set by contemporary evolutionary theory, and there’s no assurance that any interesting biological structures will be produced. Let’s nail this down more concretely.
Consider how biologists propose to explain the emergence of the bacterial flagellum, a molecular machine that has become the mascot of the intelligent design movement. In public lectures, Harvard biologist Howard Berg calls the bacterial flagellum “the most efficient machine in the universe.” The flagellum is a nano-engineered bidirectional motor-driven propeller on the backs of certain bacteria. It spins at tens of thousands of rpm, can change direction in a quarter turn, and propels a bacterium through its watery environment. According to evolutionary theory it had to emerge via some material mechanisms. Fine, but how?
The usual story is that the flagellum is composed of parts that previously were targeted for different uses and that natural selection then co-opted to form a flagellum. This seems reasonable until we try to fill in the details. The only well-documented examples that we have of successful co-option come from human engineering. For instance, an electrical engineer might co-opt components from a microwave oven, a radio, and a computer screen to form a working television. But in that case, we have an intelligent agent who knows all about electrical gadgets and about televisions in particular.
But natural selection doesn’t know a thing about bacterial flagella. So how is natural selection going to take extant protein parts and co-opt them to form a flagellum? The problem is that natural selection can only select for preexisting function. It can, for instance, select for larger finch beaks when the available nuts are harder to open. Here the finch beak is already in place and natural selection merely enhances its present functionality. Natural selection might even adapt a preexisting structure to a new function; for example, it might start with finch beaks adapted to opening nuts and end with beaks adapted to eating insects.
But for co-option to result in a structure like the bacterial flagellum, we are not talking about enhancing the function of an existing structure or reassigning an existing structure to a different function, but reassigning multiple structures previously targeted for different functions to a novel structure exhibiting a novel function. Even the simplest bacterial flagellum requires around forty proteins for its assembly and structure. All these proteins are necessary in the sense that lacking any of them, a working flagellum does not result.
The only way for natural selection to form such a structure by co-optation, then, is for natural selection gradually to enfold existing protein parts into evolving structures whose functions co-evolve with the structures. We might, for instance, imagine a five-part mousetrap consisting of a platform, spring, hammer, holding bar, and catch evolving as follows: It starts as a doorstop (thus consisting merely of the platform), then evolves into a tie-clip (by attaching the spring and hammer to the platform), and finally becomes a full mousetrap (by also including the holding bar and catch).
Design critic Kenneth Miller finds such scenarios not only completely plausible but also deeply relevant to biology (in fact, he regularly sports a modified mousetrap cum tie-clip). Intelligent design proponents, by contrast, regard such scenarios as rubbish. Here’s why. First, in such scenarios the hand of human design and intention meddles everywhere. Evolutionary biologists assure us that eventually they will discover just how the evolutionary process can take the right and needed steps without the meddling hand of design. All such assurances, however, presuppose that intelligence is dispensable in explaining biological complexity. Yet the only evidence we have of successful co-option comes from engineering and confirms that intelligence is indispensable in explaining complex structures like the mousetrap and, by implication, the flagellum. Intelligence is known to have the causal power to produce such structures. Unguided material mechanisms have never given any evidence of such causal power.
Indeed, the primary mechanism of evolutionary theory, namely, the interplay between incidental change and natural selection, looks increasingly feeble in this regard. The whole point of this Darwinian selection mechanism is to show how one can traverse biological configuration space by taking sufficiently small steps (or, as Darwin put it, “numerous successive slight modifications”). How small? Small enough that they are reasonably probable. But what guarantee is there that a sequence of baby-steps connects two points in configuration space?
Yet the problem goes deeper. For the Darwinian selection mechanism to connect point A to point B in configuration space, it is not enough that there merely exist a sequence of baby-steps connecting the two. In addition, each baby-step needs in some sense to be “successful.” In biological terms, each step requires an increase in fitness as measured in terms of survival and reproduction. (Note that without a strict increase in fitness, we are talking about a neutral theory of evolution in which searching biological configuration space devolves to a random search. Random searches are fine for breaking out of local optima or, if you will, ruts that natural selection has gotten the evolutionary process into, but because biological configuration spaces are so huge, random searches play only a minor, occasional role in evolution). Natural selection, after all, is the primary motive force behind each baby-step, and selection only selects what is advantageous to the organism. Thus, for the Darwinian mechanism to connect two organisms, there must be a sequence of successful baby-steps connecting the two.
Richard Dawkins compares the emergence of biological complexity to climbing a mountain—Mount Improbable, as he calls it (see his book Climbing Mount Improbable). He calls it Mount Improbable because if you had to get all the way to the top in one fell swoop (that is, achieve a massive increase in biological complexity all at once), it would be highly improbable. But Mount Improbable does not have to be scaled in one leap. Evolutionary theory purports to show how Mount Improbable can be scaled in small incremental steps. Thus, according to Dawkins, Mount Improbable always has a gradual serpentine path leading to the top that can be traversed in baby-steps. But such a claim requires verification. It might be a fact about nature that Mount Improbable is sheer on all sides and getting to the top from the bottom via baby-steps is effectively impossible. A gap like that would reside in nature herself and not in our knowledge of nature (it would not, in other words, constitute a god-of-the-gaps).
Consequently, it is not enough merely to presuppose that a fitness-increasing sequence of baby steps connects two biological systems—it must be demonstrated. For instance, it is not enough to point out that some genes for the bacterial flagellum are the same as those for a type III secretory system (a type of pump) and then handwave that one was co-opted from the other. Anybody can arrange complex systems in series based on some criterion of similarity. But such series do nothing to establish whether the end evolved in a Darwinian fashion from the beginning unless each step in the series can be specified, the probability of each step can be quantified, the probability at each step turns out to be reasonably large, and each step constitutes an advantage to the organism (in particular, viability of the whole organism must at all times be preserved). Only then do we have a mechanistic explanation (acceptable to evolutionary theory) of how one system arose from another. Only then can we legitimately say that unintelligent evolution is confirmed.
So, what is the alternative to unintelligent evolution? My aim in this talk has not been to proselytize for any alternative position. Unintelligent evolution remains an unsupported, speculative hypothesis. Accuracy demands that it be treated as such regardless of alternatives. Proponents of evolutionary theory regularly compare their theory favorably to the established theories of the physical sciences. Thus I’ve seen evolutionists compare their theory favorably to Einsteinian physics, claiming that it is just as well established as general relativity. Yet how many physicists, to argue for the truth of Einsteinian physics, will claim that general relativity is as well established as evolutionary theory? Zero. Unintelligent evolution is nowhere near as well confirmed as the established theories of physics and chemistry. Thankfully, it is now increasingly getting the critical scrutiny it deserves.