Darwin's Doubt

by Stephen C. Meyer

  The highly specified, tightly integrated, hierarchical arrangements of molecular components and systems within animal body plans also suggest intelligent design. This is, again, because of our experience with the features and systems that intelligent agents—and only intelligent agents—produce. Indeed, based on our experience, we know that intelligent human agents have the capacity to generate complex and functionally specified arrangements of matter—that is, to generate specified complexity or specified information. Further, human agents often design information-rich hierarchies, in which both individual modules and the arrangement of those modules exhibit complexity and specificity—specified information as defined in Chapter 8. Individual transistors, resistors, and capacitors in an integrated circuit exhibit considerable complexity and specificity of design. Yet at a higher level of organization, the specific arrangement and connection of these components within an integrated circuit requires additional information and reflects further design (see Fig. 14.2).

  Conscious and rational agents have, as part of their powers of purposive intelligence, the capacity to design information-rich parts and to organize those parts into functional information-rich systems and hierarchies. We know of no other causal entity or process that has this capacity. Clearly, we have good reason to doubt that mutation and selection, self-organizational processes, or any of the other undirected processes cited by other materialistic evolutionary theories, can do so. Thus, based upon our present experience of the causal powers of various entities and a careful assessment of the efficacy of various evolutionary mechanisms, we can infer intelligent design as the best explanation for the origin of the hierarchically organized layers of information needed to build the animal forms that arose in the Cambrian period.

  Location, Location, Location

  There is another remarkable aspect of the hierarchical organization of information in animal forms. Many of the same genes and proteins play very different roles, depending upon the larger organismal and informational context in which they find themselves in different animal groups.22 For example, the same gene (Pax-6 or its homolog, called eyeless), helps to regulate the development of the eyes of fruit flies (arthropods) and those of squid and mice (cephalopods and vertebrates, respectively). Yet arthropod eyes exemplify a completely different structure from vertebrate or cephalopod eyes. The fruit fly possesses a compound eye with hundreds of separate lenses (ommatidia), whereas both mice and squid employ a camera-type eye with a single lens and retinal surface. In addition, although the eyes of squid and mice resemble each other optically (single lens, large internal chamber, single retinal surface), they focus differently. They undergo completely different patterns of development and utilize different internal structures and nerve connections to the visual centers of the brain. Yet the Pax-6 gene and its homologs play a key role in regulating the construction of all three of these different adult sensory structures. Moreover, evolutionary and developmental biologists have found that this pattern of “same genes, different anatomy” recurs throughout the bilaterian phyla, for features as fundamental as appendages, segmentation, the gut, heart, and sense organs (see Fig. 18.2).23

  This pattern contradicts the expectations of textbook evolutionary theory. Neo-Darwinism predicts that disparate adult structures should be produced by different genes. This prediction follows directly from the neo-Darwinian assumption that all evolutionary (including anatomical) transformations begin with mutations in DNA sequences—mutations that are fixed in populations by natural selection, genetic drift, or other evolutionary processes. The arrow of causality flows one way from genes (DNA) to development to adult anatomy. Thus, if biologists observe different animal forms, it follows that they should expect that different genes will specify those forms during animal development. Given the profound differences between the fruitfly compound eye and the vertebrate camera eye, neo-Darwinian theory would not predict that the “same” genes would be involved in building different eyes in arthropods and chordates.24

  FIGURE 18.2

  The same genes can be used in different animals to produce dramatically different structures, contradicting neo-Darwinian expectations.

  Many leading evolutionary theorists have acknowledged this problem. University of Wisconsin evo-devo researcher Sean B. Carroll has noted that the neo-Darwinian prediction of similar genes producing similar structures is “entirely incorrect.”25 Stephen Jay Gould described the discovery of the polyfunctional role of similar genes as “explicitly unexpected” and “discombobulat[ing] the confident expectations of orthodox theory.”26

  The theory of intelligent design suggests a solution to the problem—a solution familiar to us from the construction and operation of our own artifacts. Figure 18.3 shows a general-purpose switching transistor. These electronic components can be used to help build many electronic systems, from a computer to a microwave oven to a radio. And the exact functional role that the transistor will play will be governed by the system in which it finds itself. (One must, of course, make allowances for the particular specifications of the transistor itself; a transistor cannot function as a battery).

  Nowhere, however, is this feature of polyfunctional modularity more intuitively clear than in our use of natural languages, such as English. To illustrate this, my colleague Paul Nelson once “disassembled” the last forty-four words of Abraham Lincoln’s Gettysburg Address (see Fig. 18.4) into a lexicon. Using the same words, at roughly the same frequency, he then wrote an “Anarchist’s Manifesto,” with a meaning diametrically opposite to that of Lincoln’s. What had changed were not the words—that is, the lower-level modules. Rather, the higher-level context, or the system as a whole, differed. Lincoln wrote with one meaning in mind, the anarchist with another—and that made all the difference to the functions of the elements, or modules, within the respective systems. Nelson calls this context dependency “the organismal context principle” when it occurs in biology and he likens it to the context dependence of words in language or low-level parts in a technological system.

  FIGURE 18.3

  A general purpose transistor—an example of a component that can be used to perform different functions in different designed systems. Courtesy iStockphoto.com/S230.

  FIGURE 18.4

  This comparison of Lincoln’s Gettysburg Address and an “Anarchist’s Manifesto” shows how the same modular elements (words) can perform different functions depending on their surrounding context, just as many genes do in biological systems. Courtesy Paul Nelson.

  He also argues that intelligent design provides a compelling explanation for the presence of polyfunctional modularity in living systems. Why? Not only is the polyfunctionality of genetic modules unexpected in a neo-Darwinian view, it is a common feature of intelligently designed systems. As Nelson and Jonathan Wells note, “An intelligent cause may reuse or redeploy the same module in different systems, without there necessarily being any material or physical connection between those systems.”27 They also observe that intelligent agents “can generate identical patterns independently” and put them to different uses in different systems of parts:

  If we suppose that an intelligent designer constructed organisms using a common set of polyfunctional genetic modules—just as human designers, for instance, may employ the same transistor or capacitor in a car radio or a computer, … then we can explain why we find the “same” genes expressed in the development of what are very different organisms… . A particular gene, employed for its DNA-binding properties, finds its functional role in a higher-level system whose ultimate origin was intelligently caused.28

  Wells and Nelson go on to explain that “the overall system, not the gene itself” determines the ultimate functional significance of the lower level modules, just as it does in all human technological or communication systems. Certainly, both the computer software and computer hardware (integrated circuits) exhibit this feature—what might be called “context-dependent, polyfunctional modularity.” Similarly, in information-rich
texts—such as the Gettysburg Address or the Anarchist’s Manifesto—humans convey different meanings with the same low-level modules (words) depending upon their surrounding context. Experience shows that when we know how systems possessing this feature arose, invariably they arose by intelligent design.

  Features of the Pre-Cambrian–Cambrian Fossil Record

  Intelligent design not only helps to explain many key features of the Cambrian animals themselves; it also helps to explain many otherwise anomalous features of the Cambrian fossil record.

  An Inverted Cone: Disparity Preceding Diversity

  As discussed in Chapter 2, the fossil record shows a “top-down” pattern in which phyla-level morphological disparity appears first followed only later by species-level diversity. Major innovations in body plans precede minor variations on basic designs.29 This “inverted cone of diversity” also suggests intelligent design.

  Neo-Darwinism seeks to explain the origin of novel body plans by starting with simpler body plans and gradually assembling animals with more complex body plans via the gradual accumulation of small successive material variations. Thus, neo-Darwinism employs a “bottom-up” mode of causation. With a bottom-up approach, small-scale diversification should eventually produce large-scale morphological disparity—differences in body plan. The “bottom-up” metaphor thus describes a kind of self-assembly in which the gradual production of the material parts eventually generates the organization of the whole. This suggests in turn that the parts stand causally prior to the organization of the whole. As I have argued, however, this approach encounters both paleontological and biological difficulties: the fossil record leaves no evidence of such a process and the morphological innovation and transformations that it requires are, in any case, biologically implausible.

  But if a bottom-up approach fails, perhaps a “top-down” approach will succeed. “Top-down” causation begins with a basic architecture, blueprint, or plan and then proceeds to assemble parts in accord with it. The blueprint stands causally prior to the assembly and arrangement of the parts. But where could such a blueprint come from? One possibility involves a mental mode of causation. Intelligent agents often conceive of plans prior to their material instantiation—that is, the preconceived design of a blueprint often precedes the assembly of parts in accord with it. An observer touring the parts section of a General Motors plant will see no direct evidence of a prior blueprint for GM’s new models, but will perceive the basic design plan immediately upon observing the finished product at the end of the assembly line. Designed systems, whether automobiles, airplanes, or computers, invariably manifest a design plan that preceded their first material instantiation. But the parts do not generate the whole. Rather, an idea of the whole directed the assembly of the parts.

  This form of causation can certainly explain the pattern in the fossil record. As new species appear in the Cambrian, they manifest completely novel, morphologically disparate, and functionally integrated body plans. Thus, although the fossil record does not directly establish the existence of a prior mental plan or blueprint, such a plan could certainly explain, or be inferred from, the top-down pattern of fossil evidence. In other words, if the body plans of the Cambrian animals did arise as the result of a “top-down” mode of causation involving a preconceived design plan, we would expect, based on our experience of complex designed systems, to find precisely the pattern of evidence that we do see in the fossil record. Further, materialistic “bottom-up” models of causation fail to explain this same pattern of fossil evidence. Thus, intelligent design provides a better explanation of this feature of the Cambrian fossil record than do competing materialistic evolutionary theories.

  The design hypothesis can also explain why smaller-scale diversity arises after, not before, morphological disparity in the fossil record or, to put it more poetically, why the basic themes of life precede the variation on those themes. Complex designed systems have a fundamental functional integrity that makes their alteration difficult. For this reason, we should not expect gradual mechanisms of change to produce new body plans or alter them fundamentally after they have arisen. We might, however, expect to find variations on these basic themes within the functional limits established by a basic architecture or body plan. Fundamentally new forms of organization require design from scratch. For example, airplanes did not arise gradually or incrementally from automobiles. Nevertheless, new innovations often accrete to novel designs provided the fundamental organizational plan is not altered.

  Since the invention of the automobile, all cars have included the same basic structural and functional elements, including a motor, at least three (and usually four) wheels, a carriage with seats for passengers, a structure connecting the wheels to the carriage, a steering wheel and column (or analogous mechanism), and a means of translating energy generated by the motor to the wheels. These are minimal requirements, of course; many cars have used axles to connect the wheels, though some have not and a “stretch” limousine may need additional axles or wheels. Indeed, though many new variations on the original model have arisen after the invention of the basic automobile design, all exemplify this same basic design. Interestingly, we also observe this pattern in the fossil record. The major animal body plans appear first instantiated by a single (or very few) species or genera. Then, later, many other varieties arise with many new features, yet all still exhibit the same basic body plan.

  Experience shows a hierarchical relationship between functionally necessary and functionally optional features in designed systems. An automobile cannot function without a motor or steering mechanism; it can function with or without twin I-beam suspension, antilock brakes, or “stereo surround sound.” This distinction between functionally necessary and optional features suggests the possibility of future innovation and variation on basic design plans, even as it imposes limits on the extent to which the basic designs themselves can be altered. The logic of designed systems, therefore, suggests precisely the kind of top-down pattern that we see in both the history of our own technological innovation30 and in the history of life following the Cambrian explosion (compare Figs. 18.5a and 18.5b). On the other hand, competing materialistic evolutionary theories would not lead us to expect the fossil record to manifest such a “top-down” pattern, but the opposite.

  Sudden Appearance and Missing Ancestors

  The theory of intelligent design can also help to account for the abrupt appearance of complex anatomical structures and animal body plans in the fossil record. Intelligent agents sometimes produce material entities through a series of gradual modifications (as when a sculptor shapes a sculpture over time). Nevertheless, intelligent agents also have the capacity to introduce complex technological systems into the world fully formed. Often such systems bear no resemblance to earlier technological systems—their invention occurs without a material connection to earlier, more rudimentary technologies. When the radio was first invented, it was unlike anything that had come before, even other forms of communication technology. For this reason, although intelligent agents need not generate novel structures abruptly, they can do so. Thus, invoking the activity of a mind provides a causally adequate explanation for the pattern of abrupt appearance in the Cambrian fossil record.

  FIGURE 18.5

  Figure 18.5a (top): A top-down pattern of appearance found in the history of animal life. Figure 18.5b (bottom): A top-down pattern of appearance in human technology.

  On the other hand, strictly materialistic theories of evolution necessarily envision a “bottom-up” mode of causation in which material parts or materially instantiated intermediate forms of organization necessarily precede the emergence of fully developed body plans. For this reason, the sudden appearance of novel animal forms contradicts the expectations of most materialistic evolutionary theories. Neo-Darwinism, in particular, would not expect the sudden appearance of animal forms. As Darwin himself insisted: “Natura non facit saltum” (“Nature takes no leaps”). Yet intelligent agents can act su
ddenly or discretely in accord with their powers of rational choice or volition, even if they do not always do so. Thus, the sudden appearance of the Cambrian animals does suggest, at least, the possibility of a volitional act of a conscious agent—a designer.

  Intelligent design likewise helps explain the absence of ancestral precursors. If body plans arose as the result of an intelligent agent actualizing an immaterial plan or idea, then an extensive series of material precursors to the first animals need not exist in the fossil record, anymore than such a series is always present in the history of technology. The radio did not evolve gradually from the telegraph. Mental plans or concepts need not leave a material trace. Thus, intelligent design can account for the dearth of material precursors in the Precambrian strata, whereas “bottom-up” materialistic evolutionary theories cannot, especially given the failure of the artifact hypothesis discussed earlier.

  Stasis (or Persistent Morphological Isolation)

  Finally, intelligent design also explains the observed stasis in the fossil record. As advocates of punctuated equilibrium established, Cambrian species tend to persist unchanged in their basic forms over time. Animal body plans that define the higher taxa, including classes and phyla, also remain especially stable in their basic architectural designs, showing “no directional change”31 over geological history after their first appearance in the Cambrian. As a result, the morphological disparity between distinct animal body plans remains unbridged. Moreover, as noted in Chapter 13, developmental mechanisms constrain the degree to which organisms may vary without deleterious consequences.