Department of Chemistry, College of Mount St. Vincent

Throughout the centuries that science has been a separate discipline, a dialogue between science and religion has taken place.  This dialogue has ranged from a simple exchange of information, to the use of religious principles for motivation in the study of science, to the use of science to try and gain reli­gious insights and possibly even to “prove religion.”  This last aspect has been most commonly seen in a movement once called Natural Theology.  Natural Theology uses science to look for the “footprints” or evidence of God.  By scientific investigations, the natural theologian tries to find those facets of the world which can seemingly only be explained by the existence of a creator God.  Before Darwin, as scientists studied the wondrous diversity of life forms on earth, the best explanation for the miracle of life was divine “intelligent design.”  In 1873 William Paley (1873) proposed that, just as the existence of an obviously designed watch implies the existence of a designer, the intricacies of living organisms must also point toward the existence of a heavenly designer.

Charles Darwin and his theory of evolution through natural selection, however, has provided an equally adequate answer to the question of origins of the great diversity of life, and one that is completely naturalistic.  Natural selection—a combination of random of variations, which we now call mutations, with the selection power of an environment that eliminates unfavorable change—can explain life’s design.  As long as there is enough time (and the four billion years that there has been life on earth seems to be enough) natural selection can accom­plish the design of all the forms of life, without recourse to the Divine, without any supernatural interventions.

Even before Darwin, Hume had addressed the Design Argument.  He pointed out that what we perceive to be design could only be the appearance of it.  Darwin provided a mechanical, naturalistic mechanism by which the diversity of life could arise without the help or input of a designer.  Natural Theology appeared to have been vanquished by Darwin’s insights, but it just wouldn’t die.  Like the Hydra that fought with Hercules, every time one head was cut off, two more grew in its place.  Natural Theology is alive and well and found in many forms today.

One current version of Natural Theology is called Intelligent Design Theory, a movement that once again tries to use scientific knowledge to “prove” the activity of God in the universe.  The basic strategy is as follows: Select and consider specific aspects of life, using relevant knowledge from current natural science.  Then ask the question of whether one can, using the best scientific know­ledge of the day, construct a credible scenario in which the particular life form came about in a gradualist, Darwinian fashion.  If not, then it must be the outcome of not a mindless, naturalistic, evolutionary process but rather a result of intelligent design.  “The precise meaning of ‘intelligent design’ is not always apparent, but it most often entails the combination of both thoughtful conceptualization and the first assembly of a new form by extra-natural means (Van Till, 1998, p. 345).”  Leaders of this movement would include Philip Johnson (1991), William Dembski (1999) and the biochemist Michael Behe (1996).  Being trained in biochemistry and molecular biology myself, I will primarily address the arguments of Michael Behe.

Michael Behe introduced what he claims to be evidence for an intelligent designer: namely the presence of “irreducibly complex” systems.  Charles Darwin stated 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 (1872, p. 154).”  Behe claims that irreducibly complex systems provide such a complex organ.  He (p. 39) describes such systems as follows:

 

By irreducibly complex, I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, where in the removal of any one of the parts causes the system to effectively cease functioning.  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 an integrated unit, in one fell swoop, for natural selection to have anything to work on.

 

Behe (p. 42) uses an analogy of a mousetrap to describe such irreducibly complex systems:

 

The function of a mousetrap is to immobilize a  mouse....The mousetraps that my family used consist of a number of parts: (1) a flat wooden platform to act as a base; (2) a metal hammer, which does the actual job of crushing the little mouse; (3) a spring with extended ends to press against the platform and the hammer when the trap is charged; (4) a sensitive catch that releases when slight pressure is applied; and (5) a metal bar that connects to the catch and hold the hammer back when the trap is charged.

 

Each of these parts is necessary for a functional mousetrap.  A trap missing any one of these would not catch mice.  The trap, having no functional precursors, could not be an improvement on an existing model (the hallmark of a system which evolves).  An isolated spring, or trap without a spring, would be incapable of catching mice.  All parts of the mousetrap have to be assembled simul­taneously for any of them to be functional.

Behe then eloquently describes a series of cellular functions that are remarkably complex, including the mechanisms for vision, blood clotting, and the immune system.  In terms of making very complicated biochemical interactions understandable to the layman, Behe does an admirable job.  These highly complex cellular systems can function as they do only if all units are simultaneously present and  working closely together in an integrated function.  Gradual emergence, where these systems evolve one component at a time, seems not to be able to explain the development of the system.  Just as the mouse­trap won’t work with even one component missing, cellular systems likewise cannot function in the absence of one component.  John Haught (2000, p.4) summarizes Behe’s conclusion by saying: “....if the cellular mechanism is not the product of gradual accumulation of small changes, then, Behe con­cludes, the Darwinian explanation of life is demon­strably erroneous.”

According to Behe, Darwinian or evolutionary explanations of such complex systems are a “black box”—some hypothetical sequence of events and mutations acted on by natural selection—and we are supposed to believe that these events will explain the world without examining them all too closely.  Behe suggests that rather than relying on a mysterious black box to explain the world, we accept the more reasonable alternative of intelligent design.

The intelligent design proponents look at life and see it as too perfect for it to have come about by chance.  But these people are betting on ignorance:  Because we cannot currently explain the evolution of complex biochemical systems, they imply that it is impossible to explain them, that the system could not have evolved and must have been designed.  This is, however, an example of “God of the Gaps” thinking, which has proven problematic before.  When people explain the gaps in scientific knowledge by God’s action, when the gap is later filled in by scientific progress, it seems to eliminate the need for God.  This “leap of faith” to a conclusion that there must be a designer is inspired by their belief in a God, and in the supernatural creation of the world and of life itself.  People of faith, coming from this Weltan­schauung, are very impressed by Behe’s irreducibly complex systems.  To believers, both laymen and scholars, Behe’s thesis seems to be compelling evidence for the existence of a designer God.

According to Behe, a system is irreducibly complex if all of its components are essential to the function of the system.  Using his mousetrap exam­ple, a trap will not catch mice if it is missing a spring, or the hammer or the wooden base.  No simpler version of the trap will be able to trap mice.  However, I remember in cartoons as a child seeing people catch mice with a much simpler device, a box with one end raised and held up by a stick, with a long string on the stick.  A person would hold the other end of the long string, waiting and watching for a mouse to appear.  When a mouse was under the box, a tug on the string would pull out the stick, and gravity caused the box to drop, trapping the mouse.

This trap could be improved by the addition of bait: a piece of cheese placed under the box would attract mice, increasing the likelihood of the mouse coming under the box, and being caught when the string was pulled.  In Boy Scouts they taught us to improve this trap once again by automating it, and by making it more lethal.  A heavy board or log with a flat surface, which crushes the little mouse against the ground, replaces the box.  This kills the mouse, rather than imprisons him, which precludes the possibility of an escape.  Rather than a person sitting and watching to pull on the string, an ar­rangement of notched sticks could both hold the bait and support the box.  When the bait is taken the sticks are disturbed and the heavy board falls, killing the mouse.

One might make this trap more sturdy by fixing the parts to one another, allowing them to move through the use of a hinge.  A firm board underneath replaces the ground which may be too soft and yielding, and the falling board is attached to the base board by a hinge.  The trap has become more efficient, more durable, and more lethal by the addition of these components.

So far this trap is still powered by gravity.  One might be inspired by the spring and clip holding paper to a clipboard, and the mousetrap takes a quantum leap forward.  Since the power of a coiled spring is much stronger than gravity, one could replace the box with a bar and spring.  The top board now falls much faster, powered by the spring.  It would even be possible to decrease the size of the falling board, since now it doesn’t require the heavy mass which was accelerated by gravity.

The hammer of the modern mousetrap replaces the box, the spring replaces gravity, and the bar holding back the hammer replaces the stick holding up the box.  The bait rigged to the bar remains basically the same, with the catch of the modern trap taking the place of my notched sticks.

Behe would argue (p. 44) that these variations of a dead fall mousetrap are not physical precursors, but merely conceptual precursors.  They perform the same task, by a different means.  I have described how all the parts of the modern mousetrap were represented in the primitive dead fall.  According to Behe, a physical precursor must be directly changed into the modern mousetrap by gradual change or improvement, and “...each change can be only a slight modification, duplication or rearrangement of a pre-existing component, and the change must improve the function....”  Replacing the box with a heavy board, and then the stick by a rod, hammer and spring is not a direct duplication or improvement of a pre-existing component, but rather an importa­tion of components from outside the system.  The trap was improved by substitution with or addition of components that existed in another system, a clip­board.

In this very objection we see the problem with Behe’s logic.  He considers each biochemical system as an isolated system, cut off from the rest of the cell, with no exchange of parts or materials possible.  The protein components of each of these biochemi­cal systems were not generated in a vacuum, but rather resulted from the duplication or modification of pre-existing proteins, which was used in another possibly related system.  These related proteins constitute protein families and super-families.  Analysis of the DNA, the molecular instructions for protein synthesis, gives us a clue as to the history and relatedness of different proteins.

Complex tasks, performed by a seemingly irreducibly complex system can be accomplished less elegantly by simpler means, as in my box mouse­trap.  These simple systems can be improved by the appropriation of other cellular components, which may add force, amplify a response, or add regula­tion.  The modified system is clearly superior, and selectable by natural selection.  Once the new components are optimally integrated into the system, it may appear to be irreducibly complex, since now the removal of one of the components from the system would render it non-functional.