Behe Responds to the Author

The Sterility of Darwinism


Michael J. Behe

Darwin v. Intelligent Design (Again) H. Allen Orr's discussion of Darwin's Black Box: Boston Review, Dec/Jan 97.

H. Allen Orr Responds Boston Review, Feb/Mar 97.


As it struggles to comprehend nature, science sometimes has to completely re-think how the world works. For example, Newton's laws apply to everyday objects but can't handle nature's tiny building blocks. Propelled by this discovery, quantum mechanics overthrew Newton's theory. Revolutions in biology have included the cell theory of life in the 19th century, as well as the slow realization in this century that cells are composites of enormously complex molecular systems.

Newton's theory remains very useful, and we can still learn many things by studying whole animals or cells. When explaining the nuts and bolts of the world, however, those views must yield to more basic descriptions. A mechanical engineer can't contradict a physicist on fundamental principles of matter. And evolutionary biology can't overrule biochemistry1 on fundamental principles of life. It's not a question of pride--that's just the way the world works.

Curiously, some people seem offended by the way the world works. In his review of my book, Darwin's Black Box: The Biochemical Challenge to Evolution, evolutionary biologist H. Allen Orr unexpectedly attempts to claim priority for his field. He grouses that pre-med students are required to take biochemistry but not evolutionary biology. He plaintively asks "Why is everyone an expert witness when the topic is Darwinism but not when it's biochemistry?" The obvious reply is that the evolution of biochemical systems is itself biochemistry. When a protein sequence changes, when DNA mutates, those are biochemical changes. Since inherited changes are caused by molecular changes, it is biochemists--not evolutionary biologists--who will ultimately decide whether Darwin's mechanism of natural selection can explain life. No offense--that's just the way the world works.

Orr hankers for the respect accorded physicists, and thinks evolutionary biologists can finally lay aside their "physics envy" because "we biologists have discovered the structure of DNA, broken the genetic code, sequenced the entire genome of some species . . ." Orr is like a podiatrist claiming credit for progress in brain surgery. Biochemistry made those dramatic advances; evolutionary biology played no part. I mean no disrespect, but this is not a minor academic turf war--the point is crucial. Anyone who wants to address questions about life's basic mechanisms has to do so from a molecular perspective. Orr does not.

Declining the opportunity to address my biochemical arguments, Orr questions the concept of irreducible complexity on logical grounds. He agrees with me that "You cannot . . . gradually improve a mousetrap by adding one part and then the next. A trap having half its parts doesn't function half as well as a real trap; it doesn't function at all." So Orr understands the point of my mousetrap analogy--but then mysteriously forgets it. He later writes, "Some part (A) initially does some job (and not very well, perhaps). Another part (B) later gets added, because it helps A." Some part initially does some job? Which part of the mousetrap is he talking about? A mouse has nothing to fear from a "trap" that consists of just an unattached holding bar, or spring, or platform, with no other parts.

I do sympathize with Orr's muddling of the analysis. The concept of irreducible complexity is new, and can be difficult to grasp for people who have always assumed without demonstration that small, continuous changes could produce virtually any biological structure. Perhaps in the future that assumption will not have such a strong hold on the minds of evolutionary biologists.

Having completed his logical analysis, Orr turns to the topic of gene duplication: "So how does Behe explain duplicate genes? He doesn't." But I do. I discuss them on pages 89-90 of my book, concluding "The sequence similarities are there for all to see. . . . By itself, however, the hypothesis of gene duplication . . . says nothing about how any particular protein or protein system was first produced." For example, the DNA in each of the antibody-producing cells of your body is very similar to that of the others, but not identical. The similarities are due to common descent; that is, all the cells in your body descended from one fertilized egg cell. The differences, however, are not due to Darwinian natural selection. Rather, there is a very clever, built-in program to rearrange antibody genes. Billions of different kinds of antibody genes are "intentionally" produced by your body from a pre-existing stock of just a few hundred gene pieces. Perhaps because of his unfamiliarity with molecular systems, Orr has trouble seeing that similarity in gene sequences may indicate common ancestry, but is not itself evidence that a system was constructed by natural selection.

To test natural selection requires much more evidence than mere sequence similarity: it requires experimentation. In all of the scientific literature, however, no experimental evidence can be found that natural selection can produce irreducibly complex biochemical systems. To rebut my arguments Orr could simply have cited papers in the science literature where the systems I discuss have been explained. He didn't do that because explanations are nowhere to be found.

What has biochemistry found that must be explained? Machines--literally, machines made of molecules. Let's look at just one example. The flagellum is an outboard motor that many bacteria use to swim. It consists of a rotary propeller, motor, and stationary framework. Yet this short description can't do justice to the machine's full complexity. Writing of the flagellum in Cell,2 Lucy Shapiro of Stanford University marvels, "To carry out the feat of coordinating the ordered expression of about 50 genes, delivering the protein products of these genes to the construction site, and moving the correct parts to the upper floors while adhering to the design specification with a high degree of accuracy, the cell requires impressive organizational skills." Without any one of a number of parts, the flagellum does not merely work less efficiently; it does not work at all. Like a mousetrap it is irreducibly complex and therefore cannot have arisen gradually.

The rotary nature of the flagellum has been recognized for about 25 years. During that time not a single paper has been published in the biochemical literature even attempting to show how such a machine might have developed by natural selection. Darwin's theory is completely barren when it comes to explaining the origin of the flagellum or any other complex biochemical system.

The sterility of Darwinism indicates that it is the wrong framework for understanding the basis of life. As I argue in my book, an alternative hypothesis is both natural and obvious: systems such as the flagellum were intentionally designed by an intelligent agent. Just as in the everyday world we immediately conclude design when we see a complex, interactive system such as a mousetrap, there is no reason to withhold the same conclusion from interactive molecular systems. This conclusion may have theological implications that make some people uncomfortable; nonetheless it is the job of science to follow the data wherever they lead, no matter how disturbing.

One last charge must be met: Orr maintains that the theory of intelligent design is not falsifiable. He's wrong. To falsify design theory a scientist need only experimentally demonstrate that a bacterial flagellum, or any other comparably complex system, could arise by natural selection. If that happened I would conclude that neither flagella nor any system of similar or lesser complexity had to have been designed. In short, biochemical design would be neatly disproved.

Let's turn the tables on Orr. Is natural selection falsifiable? He writes, "We have no guarantee that we can reconstruct the history of a biochemical pathway. But even if we can't, its irreducible complexity cannot count against its gradual evolution. . . ." This is a dangerously antiscientific attitude. In effect he is saying, "I just know that phenomenally complex biochemical systems arose gradually by natural selection, but don't ask me how." With such an outlook, Orr runs the risk of clinging to ideas that are forever insulated from contact with the outside world.

After reading Robert Berwick's criticism of Climbing Mount Improbable, I find myself in the odd position of sympathizing with Richard Dawkins. Although his book is a juicy target for debunking, Berwick chides Dawkins for all the wrong reasons. Berwick points out that natural selection is sometimes not a complete explanation for some biological feature. For example, he writes that polioviruses have shapes like geodesic domes not because selection made them that way, but because the symmetrical shape is required by physical law. Well, fine. But there are many tasks a virus faces that are not explained at all by simple physical laws: The virus has to attach to a cell surface, inject its genetic material into the cell, hijack the cell's machinery, make copies of the poliovirus DNA, and re-package the genetic material. In response the body's immune system launches a counterattack to ferret out and destroy the virus. None of these processes is explained by simple physical constraints. Berwick seems mesmerized by the simple crystal that covers nature's watch, and ignores the complex ticking gears of the mechanism within. Dawkins's writing should be roundly criticized for failing to answer the question he has set himself: what is the origin of biological complexity? But, to his credit, Dawkins at least knows the important question. Berwick doesn't.


Notes

1. By biochemistry I mean all sciences that investigate life at the molecular level, including molecular biology, much of embryology, immunology, genetics, etc. return to text

2. Lucy Shapiro, "The Bacterial Flagellum: From Genetic Network to Complex Architecture," Cell 80 (1995): 525-27. return to text

Copyright © 1997 Michael Behe. All rights reserved. International copyright secured.