Intelligent design: The biochemical challenge to Darwinian evolution?
"For since the creation of the world God's invisible qualities-his eternal power and divine nature-have been clearly seen, being understood from what has been made, so that men are without excuse" (Romans 1:20, NIV).
The question of the origin of life on this planet is a fascinating one. Did life begin on the surface of a cooling planet amidst the havoc of a restless environment racked by violent lightning flashes and volcanic activity? Did life flourish on Earth after being transported here as bacteria-like organisms deep within the crevices of a meteor? Or is life the product of an intelligence, orchestrating life by design and careful planning? Is there evidence of that design in nature and can such evidence be used to infer the existence of a Creator, as the Bible teaches?
Design in nature
Theologians and scientists have argued for centuries that certain natural features of our world are difficult to explain purely in naturalistic terms. The most famous of the design arguments is that of Paley's watchmaker. If you were to find a watch while crossing a field, what would you suppose about the origins of that watch? Would you think that the parts had all come together by chance, or would you suspect that the watch was the product of a watchmaker and that someone had dropped the watch as he or she passed by? Paley argues that because of the intricate design and function of the timepiece, there must have been a designer, "who formed it for a purpose which we find it actually to answer, who comprehended its construction and designed its use."1
Darwin's black box
A new era in design arguments dawned in 1996 with the publication of Darwin's Black Box: The Biochemical Challenge to Evolution by Michael Behe, professor of biochemistry at Lehigh University in Pennsylvania. In Darwin's day, biologists knew very little of the complex biochemistry of living organisms. What we have learned since then about the highly elaborate biochemical systems suggests a level of sophistication that defies an explanation for their existence by evolutionary mechanisms.
Up until now, design theories have not fared well in academic circles, partly because creationists have not developed theories that could be empirically tested and examined by the scientific community. For a scientific paradigm to shift, there has to be a new paradigm available to take its place. New paradigms are now being developed, and design arguments are increasingly being supported by conventional scientific arguments.
Behe begins his examination of biochemical systems with an unusual illustration--a mousetrap. It consists of five parts: a wooden base, a spring, a hammer (to break the mouse's back), a sensitive catch (which releases when slight pressure is applied) and a metal bar (which connects to the catch and holds the hammer back when the trap is charged).2 This simple mechanical system is an example of what Behe calls an irreducibly complex system since all the components must be present for it to operate as designed.
Evidence of design in biochemical and molecular systems
Molecular biology focuses on the universe within--the make-up of the cell. In recent times extraordinary advances have been made in the understanding of cell structure and function at the molecular level. The cells of an organism depend on their biochemistry for function. Metabolism (the sequence of chemical reactions upon which life depends) is highly organized and purposeful; often biochemical events are organized in a stepwise or sequential series of reactions. A specialized class of protein molecules called enzymes mediates the conversion of one target molecule (chemical substrate) into another, which is in turn worked on by the next enzyme in the sequence. These sequences resemble the assembly line of a factory; each worker along the line uniquely modifies the product being assembled. Thus each enzyme, or assembly line worker, depends on the previous one for its activity. Removing or disabling one enzyme in a biochemical pathway effectively shuts down that pathway, as there will be no more molecules produced for the next enzyme in the sequence. Such pathways are irreducibly complex, much like Behe's mouse-trap. It is difficult to envisage how such pathways could have evolved, especially if the final product of a pathway is the energy required by the cell to function. As Behe states, irreducibly complex systems "would be a powerful challenge to Darwinian evolution. 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."3
Deoxyribonucleic acid or DNA, the genetic material, is like the hard disk of a computer, containing all the programs and information needed at various times during the life of a cell. One type of enzyme, RNA polymerase reads the chemical code of a section of DNA (a gene) and sets in motion an exceedingly complex chain of events culminating in the formation of a protein molecule derived from that information. The code read by RNA polymerase in DNA determines the order of amino acids in the protein molecule to be manufactured, which in turn determines its three-dimensional shape and hence function. In terms of the flow of genetic information, one can consider this relationship between the DNA code, the order of amino acids in protein, and the shape and function of the protein itself, to be irreducibly complex. Thus, information in DNA determines the structure, shape, and function of enzyme molecules, which in turn determine which chemical substrate it may interact with in a biochemical pathway. Interference with the transmission of this information at any point will dramatically alter the final enzyme product and can mean that the enzyme produced cannot take its place in the biochemical assembly line for which it is intended, or, dare we say, designed. The resulting failure of a biochemical pathway can be fatal to the cell.
DNA can also be completely replicated so that genetic information can be passed on to daughter cells at cell replication and on a grander scale to an organism's offspring. DNA stores the information needed to synthesize the enzymes needed to replicate itself, a perfect example of irreducible complexity. Thus DNA codes for the DNA replicating enzyme, DNA polymerase. DNA polymerase reads the chemical code of DNA and faithfully creates another exact duplicate molecule. So for its existence, DNA is dependent on DNA polymerase, the existence of which is dependent on DNA itself. (See Figure 3.)
There are seemingly endless examples of design in molecular systems. Behe discusses a number of these complex systems at length, including blood clotting systems, bacterial flagella, and a variety of other biochemical systems.4
Origin of the primordial cell
But how did biochemical systems come to exist, in the first place? How did life arise on this planet? The work of Stanley Miller and Harold Urey at the University of Chicago during the early 1950s set the groundwork for the concept of chemical evolution.5 Their experiments replicated what was postulated to be the atmosphere of primitive Earth. They subjected a mixture of gases to high voltage discharges simulating lightning. Any organic molecules produced were trapped and removed from the reaction system for analysis. A small variety of simple organic compounds were detected, and it was postulated that they were the precursors of biological macromolecules forming the structure of the first primordial cell. The validity and meaning of such experiments are now under scrutiny.6 The concept of forming biological building blocks from inorganic chemicals by naturalistic processes poses enormous problems. Klaus Dose comments: "More than 30 years of experimentation on the origin of life in the fields of chemical and molecular evolution have led to a better perception of the immensity of the problem of the origin of life on earth rather than to its solution. At present all discussions on principal theories and experiments in the field either end in stalemate or in a confession of ignorance. New lines of thinking and experimentation must be tried."7
Leaving aside the technical problems of such chemistry, what would a primordial cell need to survive, replicate, and to get the evolutionary ball rolling? First, a method for capturing energy (e.g.: photosynthetic organisms that make their own food) or a mechanism for utilizing energy derived from pre-formed organic molecules. Both methods involve very complex biochemistry even in the simplest of organisms. Second, a membrane to keep the outside environment separate from the metabolic reactions within the cell. Third, a system by which genetic information can be stored and accessed (DNA). Fourth, a mechanism to convert this information into the molecular tools the cell requires to function. Finally, the all-important requirement for cellular division and self-replication. The stored genetic information must be replicated and passed onto daughter cells in order to produce descendant life forms. (See Figure 4.)
These processes are of staggering complexity despite the apparent "simplicity" of the first theorized primordial cells. For such cells to exist, metabolic systems must function and coordinate with the other systems. The primordial cell, like any other, would depend on its energy-generating biochemistry in order to operate crucial metabolic processes and synthesize essential molecules. As mentioned, information for molecular synthesis is stored in DNA. Energy generated by the cell is required for DNA synthesis and cellular replication. DNA synthesis depends upon enzymes whose blueprint is contained in DNA. None of these systems could function if it were not for the cell membrane separating the cell's biochemical reactions from the external environment. Indeed, enzymes encoded by information in DNA direct synthesis of the membrane itself--irreducible complexity at its best.
Few suggested mechanisms satisfactorily explain the molecular evolution of individual biochemical systems, let alone explain how such interdependent systems would develop in a coordinated fashion with a common goal in mind: the development of a functional cell. In his book, Behe analyzes published scientific literature on mechanisms of molecular and biochemical evolution. He also examines papers published in the Journal of Molecular Evolution (JME) since its founding in 1971. His conclusion: None of the papers published in JME over the entire course of its life as a journal has ever proposed a detailed model by which a complex biochemical system might have been produced in a gradual, step-by-step Darwinian fashion.8
Detecting intelligent design
Behe's biochemical challenge to Darwinian evolution has made a significant impact on the scientific community. His book was reviewed in prestigious scientific journals such as Nature. Here was a credible, well-informed biochemist with an argument that could not be easily dismissed. Darwin had admitted that "if it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous successive, slight modifications, my theory would absolutely break down."9
Behe's renewal of the intelligent design argument has been strengthened by another design theorist, William Dembski. One of the major criticisms of Behe's book was that even though living things may look like they are designed, there is no scientific way of determining whether they are. Evolutionists who have serious objections to the design movement accept that nature appears to be designed. Richard Dawkins states in his book The Blind Watchmaker: "Biology is the study of complicated things that give the appearance of having been designed for a purpose"; and "Natural selection is the blind watchmaker, blind because it does not see ahead, does not plan consequences, has no purpose in view. Yet the living results of natural selection overwhelmingly impress us with the appearance of design as if by a master watchmaker, [they] impress us with the illusion of design and planning."10
Dembski, however, has proposed a scientific method for detecting intelligent design. He claims that this is not new to science, since forensic scientists use such an approach to distinguish chance events from criminal activity. Scientists, in their search for extraterrestrial life, must distinguish between random signals and those that might carry encoded messages from outer space. Dembski claims that intelligent design is empirically detectable. His method of detecting intelligent design takes the form of a three-stage explanatory filter.11 The filter asks three ordered questions in relation to an observed event. Is it best explained by natural law, chance, or design?
If there is a high probability of the event occurring, it is likely to be the result of a scientific law (e.g.: an object falls under the influence of gravity). If there is only an intermediate probability of the event occurring, it may be better explained by chance. If, however, there is a small probability of the event occurring, we move to the next level of the explanatory filter: design. Not all such events require intelligent design, and extremely unlikely events may occur naturally. But complex situations, such as the development of a self-replicating primordial cell that require many, many remote chance events to occur, are better explained by design rather than chance.
Criticisms of the design argument
While Behes idea of irreducible complexity has appeal at the molecular level of life, problems arise when we consider life at the level of entire functional organisms. Irreducibly complex biochemical systems are also the basis of a functioning predator or parasite. Much of nature is built on a system of predation, death, and decay, so we are tempted to ask, What sort of God would create that? According to Romans 1:20, God's character is revealed in nature, but what does a predator like a lion teach us about God? Darwin asked the same questions and concluded that there was just "too much misery in the world" to accept design: "I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae [wasps that capture caterpillars and paralyse them for their larvae to parasitize and eventually kill] with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice."12
Dembski's response to this criticism is that design does not have to be perfect. We recognize computer software or operating systems such as Windows as being designed, but most people find them to be less than perfect. From a scientific perspective, Dembski argues that just because nature doesn't appear to us to be perfect, it doesn't mean that design cannot be detected. Theology tells us that evil has entered this world and what we see now is not what God initially intended, so we should expect to see a creation that shows evidence of a good designer but also evidence of it having been perverted by evil.
So what do recent developments in the design argument teach us? For many observers, a beautiful sunset, a rocky mountain stream, or the flight of a bird will be evidence enough that God exists. Speaking for ourselves, our study of biology continues to inspire awe at the amazing complexity and beauty of life. We concur with the writer of Romans that God is adequately revealed in nature. But while Christians may be convinced that design in nature points to a Creator-God, the general scientific community has not been persuaded. Perhaps more scientifically respectable work on intelligent design of the kind done by Behe and Dembski will encourage evolutionary scientists to look beyond purely naturalistic mechanisms to explain the complexity and meaning of life. If evolutionary scientists are convinced that naturalism is limited in its explanatory power and that there is evidence for an intelligence behind the universe, then perhaps they will be open to consider that this intelligence is the God of the universe who wants a deep and personal relationship with His crowning creative masterpiece--human beings.
Evan Ward (Ph.D., New South Wales University) and Marty Hancock (Ph.D., Griffith University) are senior lecturers in the Faculty of Science and Mathematics at Avondale College, Cooranbong, NSW, Australia. E-mail: firstname.lastname@example.org
Notes and references
- W. Paley, Natural Theology (New York: American Tract Society, 1928), pp. 9, 10.
- M. J. Behe, Darwin's Black Box: The Biochemical Challenge to Evolution (New York: The Free Press, 1996), pp. 42-44.
- Ibid., p. 39.
- Ibid., chapters 4-7.
- S. L. Miller and L. E. Orgel, The Origins of Life on Earth (Upper Saddle River, N. J.: Prentice-Hall, 1974); Miller, "Which Organic Compounds Could Have Occurred on the Pre-Biotic Earth?" Cold Spring Harbour Symp. Quant. Biol. 52 (1987): 17-27.
- Behe, pp. 166-170; S. C. Meyer, "The Explanatory Power of Design: DNA and the Origin of Information," in W. A. Dembski (ed.), Mere Creation: Science, Faith and Intelligent Design (Downers Grove, Il.: InterVarsity Press, 1998), pp. 116-119; W. L. Bradley and C. B. Thaxton, "Information and the Origin of Life," in J. P. Moreland (ed.), The Creation Hypothesis (Downers Grove, Il.: InterVarsity Press, 1994), pp.173-196.
- K. Dose, "The Origin of Life: More Questions Than Answers." Interdisciplinary Science Reviews 13 (1988): 348-356.
- Behe, p. 176.
- C. Darwin, Origin of Species, first published 1872; 6th ed. (New York: New York University Press, 1988), p. 154.
- R. Dawkins, The Blind Watchmaker (London: W. W. Norton, 1985), pp. 1, 21.
- W. A. Dembski (ed.), Mere Creation: Science, Faith and Intelligent Design (Downers Grove, Il.: InterVarsity Press, 1998), pp. 98-108.
- Charles Darwin, cited in W. A. Dembski, "Intelligent Design Is Not Optimal Design" 2000. Discovery Institute internet site: http://www.discovery.org.