Microcosm_ E. Coli and the New Science of Life - Carl Zimmer [79]
Behe uses a few examples to illustrate irreducible complexity. The flagellum is one of his favorites. He claims it is obviously too complex to have evolved from a simpler precursor. Faced with the wonder of the flagellum, Behe writes, “Darwin looks forlorn.”
At the Dover trial, Behe had a textbook illustration of E. coli’s flagellum projected on the courtroom screen, and he proceeded to marvel at it all over again. “We could probably call this the Bacterial Flagellum Trial,” a lawyer for the school board said.
Behe inventoried the flagellum’s many parts and told Judge Jones that Darwinian evolution could not have produced its irreducible complexity. “When you see a purposeful arrangement of parts, that bespeaks design,” he said. The flagellum, Behe explained, was built for a purpose—to propel bacteria—and it was built from many interacting parts, just like the outboard motor of a boat. “This is a machine that looks like something that a human might have designed,” he said.
The plaintiffs’ witnesses were eager to talk about the flagellum as well, in order to demolish Behe’s claims about irreducible complexity. Kenneth Miller, a biologist at Brown University, pointed out that Behe’s claims about irreducible complexity could be tested. Behe, Miller reminded the court, had defined an irreducibly complex system as one that would be nonfunctional if it were missing a part. Miller then showed the court a computer animation of the flagellum. He began to dismantle it, removing not just one part but dozens. The filament disappeared. The universal joint vanished. The motor slipped away. All that was left when Miller was done was the needle that injects new parts of the filament into the shaft.
Miller had removed a great deal of an irreducibly complex system. By Behe’s definition, what remained should no longer be functional. But it is. The ten proteins that make up the needle are nearly identical in both their sequence and their arrangement to a molecular machine known as the type III secretion system. This is the needle used by E. coli O157:H7 and other disease-causing strains to inject toxins into host cells.
“We do break it apart, and lo and behold, we find—actually we find a variety of useful functions, one of which I have just pointed out, which is type III secretion,” Miller testified. “What that means, in ordinary scientific terms, is that the argument that Dr. Behe has made is falsified, it’s wrong, it’s time to go back to the drawing board.”
Behe tried to play down Miller’s testimony. When Behe said that a system became nonfunctional when it lost a part, he now claimed, he had meant that it lost its particular function. By removing part of the flagellum, Behe argued, Miller was left with something that could not propel a microbe. “If you take away those parts, it does not act as a rotary motor,” Behe said.
He then claimed that most people would assume Miller was implying that a type III secretion system evolved into a flagellum, something evolutionary biologists were not agreed on. Some had raised the possibility that the flagellum had evolved into a type III secretion system or that both structures evolved from a common ancestor. Yet Miller had not said anything of the sort. He had simply tested Behe’s claims, carefully hewing to Behe’s own words. And Behe’s claims had not held up to the evidence.
Over the course of the trial it became clear that Behe had some strange demands for scientists who would