A Critique of Behe's Mousetrap Illustration,
and a Critique of Behe's Critics,

Revision 12/28/2000
by Creationist, Don Stoner (Donald Wayne Stoner)

Micheael J. Behe's book, Darwin's Black Box: The Biochemical Challenge to Evolution, (Simon & Schuster, N.Y., C. 1996), documents several biological structures which appear to have a level of design complexity that cannot be further reduced without destroying their functionality. This makes such structures difficult to explain using Darwin's descent with modification in small steps.

To illustrate the concept, Behe suggests that these biological structures are analogous to a standard mousetrap (and several other mechanical devices). A mousetrap has many separate interacting components which, he claims, could not have been developed gradually. Behe implicitly challenges his readers to explain, for example, how a primitive mousetrap, involving a box propped up with a stick, could be improved by a succession of slight modifications until the standard mousetrap was obtained; each modification must be slight and each must represent a functional improvement over the previous design. (See Darwin's Black Box, pp. 39-48.) It will be shown below that the standard mousetrap is not a valid example of irreducible complexity. This does not automatically prove that Behe's biochemical examples are invalid, but it does weaken his presentation; and, paradoxically, it also suggests an interesting challenge to Behe's critics.

Gradually Improving a Mouse Trap

I will begin with a simple box and stick trap. If it doesn't come equipped with bait, we could start with the very slightest hint of bait (a mere glancing brush of actual bait) that leaves a marginal hint of an appealing aroma - which can then be gradually increased until the trap is properly baited.

The trap could then be improved, one small step at a time, by adding a tiny wooden base and enlarging it until it closed off the entire area under the box. Each increase in the size of the base would make it more difficult for the mouse to squeeze out under the edge or to burrow out. The first piece of wood could be an unnecessary piece broken loose from the box itself. The box could be given this "extra" wood in small increments with each increment adding to the weight of the box - making it harder for the mouse to lift the box. When the first piece is broken free from the box, depending on where it landed, it could do more good keeping the mouse from burrowing out than the small amount of incremental weight would have done.

Once we have increased the base until it covers the bottom of the box, we can further improve the trap by anchoring the box so the mouse can't slide it off the base. This anchoring can be accomplished by raising little ridges on the base on each side of the edge of the box which touches that base when the trap is armed. The ridges can be increased, improving their effectiveness, and even pinched together into indentations made into the box until a hinge is created - each step improving the anchoring of the box. The hinge could as easily be grown as a peg out of the box entering an indentation in the base, or as a combination of both.

Next we can start to add a spring. This spring could start out as a peg grown out of the box into a socket to help anchor the box. When the peg and socket became sufficiently long, improving anchoring the whole time, they could begin to add some spring action as the box was tipped farther back. This new spring could be improved, one little bit at a time, until it holds the box firmly down. Each incremental amount of spring strength does two separate things: 1) it holds the other edge of the box down more firmly and 2) makes the box drop more quickly, giving the animal less time to escape before the trap closes. A spring which starts out as a straight whisker can be grown into a coil, one degree at a time.

Once the box is spring loaded (instead of by gravity) we can make the stick longer, tipping the box up higher, making the entrance to the trap larger and, thus, less threatening in appearance. With the longer travel, the box comes down harder, striking more like a hammer. It becomes possible to pinch or crush the mouse and it is no longer necessary that the mouse be entirely within the area of the box for the trap to work. It also gives the mouse no time to work out an escape. The trap can be further improved by reducing the size of the box so it hits the mouse an increasingly larger percentage of the time. When the box is small enough, it will always hit the mouse.

Once we have a hammer trap instead of a box trap, the hammer can be trimmed down, giving it less mass and air drag, making it close more quickly. The rectangular frame is all that is really necessary. Increasing the spring strength also makes the hammer work more quickly. Moving the bait and stick closer to each other, ultimately connecting them, improves the likelihood of the trap operating correctly.

As the hammer is moved farther back (against the spring), the stick becomes more difficult to anchor unless an area of the base is gradually raised making a sort of hook. The hook could be made increasingly flexible and the bait attached more directly to it (and less to the stick) so that smaller tugs from the mouse would release the stick. A lever could be grown from the hook (with the bait connected to it's free end) to give the mouse an additional mechanical "advantage." At this point it would be fair to identify the hook with the "catch" on a standard mousetrap.

Now we can make the stick longer still, pushing the frame all the way back, giving the hammer a longer and more powerful swing. The catch can also be moved partway to the hinge, helping to accomplish the same end and better centering the mouse in the target area. At some point it becomes helpful to secure the top end of the stick to the hammer by producing a hinge as we did before. This reduces false triggers from the wrong end of the stick. At this point it would be fair to identify the stick with the "holding bar" on a standard mousetrap.

Now we have a trap so much like the modern mousetrap that any final changes might seem unnecessary. Still, there appears to be some gain to be had from moving the hinge on the top end of the holding bar from the hammer to the base. If the hammer is pushed all the way back, this is a very short physical distance (although it is a quantum leap). This reduces the force the holding bar applies to the catch and makes the trap spring more easily. It also reduces the chance of the holding bar pushing the mouse out of the way when the trap is sprung.

With this change, the catch design must also change from holding a strong horizontal force to a weak vertical one. Because the horizontal-holding catch must keep the stick from accidentally slipping off "sideways" (either vertically or horizontally) it is likely that an optimized horizontal-holding catch will also work as a vertically holding catch with a much lower load requirement.

At this point we have produced the modern mousetrap from the box and stick by a sequence of very small changes, each change improving the effectiveness of the trap. The final step appears the most "unlikely" (from a naturalistic position) and the most creative step in the process; still it requires a very small physical change. If this step is too large a conceptual leap, the previous design, excluding this step, is still very much like a modern mousetrap.

Conclusions and Consequences to Behe's Critics:

As I mentioned earlier, Behe's error does not automatically prove that the biochemical examples which he has presented are invalid. Instead, refuting the mousetrap claim demonstrates how easily his examples could, in principle, be refuted. Even though the modern mousetrap is obviously a product of design, it is still possible to dream up a plausible mythological history which meets Darwin's gradualistic requirements.

All that would be required of any naturalistic evolutionist who might choose to refute Behe's argument is to produce a plausible sequence whereby a few of Behe's structures could have come about gradually. It would not be necessary to do this for all of his structures, merely enough of them to illustrate any systematic weakness. Furthermore, burden of proof does not require that the single historically correct explanation be produced; all that is required is a plausible fantasy, like the one I have just generated. As I have shown, this can be possible even if the structure in question is a product of intelligent design. I question why this has not (to my knowledge) yet been done. It is possible that creationistic theories, Behe's included, are simply not taken seriously by most of the scientific community. Perhaps it is just laziness, or perhaps something more dangerous. It is as if evolution is becoming a crucial component of a shoddy religion - a dogma which must be accepted without doubt - without even as much as a willingness to objectively test its weaknesses.

Perhaps, historically, men have been too willing to attribute to God anything they did not understand. It has certainly been a step in the right direction to eliminate the host of deity from our explanations for thunder and other elusive phenomena. But to what extent does it make sense to extrapolate this trend? Is the modern genetic engineer right in denying the possibility of an intelligent designer when he himself is such a being? Can the string theorist rationally deny the existence of an unseen extra dimensional reality when his theories presume its existence? At what point does the unqualified denial of God become more absurd than the unsupported presumption of the same?

Although Behe may have selected a poor mechanical illustration, I think it possible that his biological structures might actually be beyond the reach of any gradualistic explanation - either true or fantasy; they might, potentially, constitute physical proof for a creator. But whether or not his assertion is the truth, it is now up to the naturalistic evolutionists to show how these structures might be gradualistically achieved. This is a necessary step before there can be any complete naturalistic theory of biological evolution. Perhaps, like his mousetrap, Behe's biological structures will, eventually, yield to gradualistic explanations. Until then, we must allow, even in our classrooms and textbooks, that he might be right.

If Behe's structures do yield to gradualistic explanation, another obvious hurdle for the strict naturalist is to present a plausible explanation for the first self-replicating life. Some plausable pathway from chemistry to life must be provided before there can be any complete naturalistic theory of biological origins. For a good layman's analysis, quantitizing some difficulties with biological origins, I recommend evolutionist Robert Shapiro's book, Origins, a Skeptic's Guide to the Creation of Life on Earth, (Summit Books, N.Y., C. 1986).

Until such hurdles have been successfully overcome, perhaps it is best to let the modern "Galileos," and other heretics, of our day be heard. Even in the classroom.

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Don Stoner
C/O Answers in Action