Behe is a biochemist at Lehigh University in Pennsylvania and clearly says that he accepts a lot of evolution, so much so that he should get in plenty of trouble with "old-time religion" creationists. However, Behe draws the line at the molecular level: while evolutionists might be able to explain how humans descended from other primates, and might even have a good explanation for the evolution of the eye, they can't tell us how complex biochemical pathways came into existence. Take blood clotting, for example. In order for the blood to coagulate when a cut through the skin is made, several proteins have to act in a precise sequence. Take any of them out, and you bleed to death. Or consider the flagellum of a bacterium (the "tail" that allows some bacteria to swim). It is made of several parts intricately interconnected to each other. Again, take one of them away, and the bacterial cell will be stuck in place forever. But, notices Behe, evolution is supposed to work gradually and to assemble structures that work at every single step (since it cannot predict the future use of something). This creates an apparent paradox whence a mindless natural force is supposed to come up with something that smells terribly of intelligent design. Isn't this a deathblow to evolution as the explanation of life's "irreducible" complexity?
Not so fast. There are a few things missing from Behe's scenario which are worth considering briefly. First, he has not done his homework. Contrary to what he repeatedly claims in his book, biologists have done a bit of research on the evolution of biochemical pathways, and there are several known examples of bacterial flagella that are simpler than the one Behe conveniently uses. It doesn't take a rocket scientist (or a biochemist) to figure out that in fact these simpler versions could easily represent intermediate steps toward complex flagella. Second, it is not true (again contra Behe) that biochemical pathways are assembled in a way that one cannot take any element away without having the whole system collapsing. In fact, most of genetical research is based on the ability to produce mutations that knock down certain genes (and therefore certain components of biochemical pathways) while still yielding a functional organism to be studied. One of the major discoveries of 20th century molecular biology (which Behe must have somehow missed) is that organisms are not irreducibly complex at all; rather, they show redundant complexity: they are made of several parts that have no unique and irreplaceable function. As biologist Francois Jacob put it, this is exactly what you would expect if natural selection worked like a bricoleur rather than a cunning engineer. A bricoleur is somebody who assembles new things out of old parts that are easily available. The result is bound to be complex, redundant, suboptimal, and not too pretty. Exactly like living organisms, and precisely what you would expect from a natural phenomenon. No intelligent design required.
Behe makes at least two fundamental mistakes in his attack against evolutionary biology (other than neglecting to check the available literature more thoroughly). Perhaps the subtler of the two is that he completely ignores the fact that evolutionary biology deals with historical as well as current events. If one picks a modern organism, say a bacterium of the species Escherichia coli, and tries to imagine how it could have evolved, one is up against a huge problem: what you see today under the microscope is not a "primitive" organism, but the result of (literally) billions of years of change. As we know from organisms that actually leave fossils (contrary to most bacteria), more than 99% of the species that ever existed went extinct. Since most of these don't leave fossils (especially bacteria), we are lucky if we see a few intermediate links at all, alive or in the fossil record. No wonder that evolution may look like a series of huge jumps that could not possibly have been the result of natural selection. Yet Behe behaves as if we didn't know anything about extinction and evolution, and bases his argument on an extremely naive picture of biological research and of science in general.
The second fatal mistake is common to all versions of Intelligent Design: the whole approach is essentially based on an argument from ignorance. Let us assume that biologists really don't have the foggiest about the way a particular biochemical pathway (aerobic respiration in mitochondria, for example) came about. What is that supposed to prove? If Behe were alive at the time of Aristotle, would he be arguing that lightning is clear proof of Zeus' existence because we have no idea of how a natural phenomenon could possibly provoke such a sudden discharge of energy? And yet this is exactly what the core of Behe's argument is: since we don't know how it happened, it must have been God. Sorry, Michael, but science is about working hard to find the answers. Bailing out while invoking a Deus-ex-machina is not the name of the game.
