Forum Sceptique

Richard Dawkins a écrit :I had expected to be as irritated by Michael Behe’s second book as by his first. I had not expected to feel sorry for him. The first — “Darwin’s Black Box” (1996), which purported to make the scientific case for “intelligent design” — was enlivened by a spark of conviction, however misguided. The second is the book of a man who has given up. Trapped along a false path of his own rather unintelligent design, Behe has left himself no escape. Poster boy of creationists everywhere, he has cut himself adrift from the world of real science. And real science, in the shape of his own department of biological sciences at Lehigh University, has publicly disowned him, via a remarkable disclaimer on its Web site: “While we respect Prof. Behe’s right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally and should not be regarded as scientific.” As the Chicago geneticist Jerry Coyne wrote recently, in a devastating review of Behe’s work in The New Republic, it would be hard to find a precedent.

For a while, Behe built a nice little career on being a maverick. His colleagues might have disowned him, but they didn’t receive flattering invitations to speak all over the country and to write for The New York Times. Behe’s name, and not theirs, crackled triumphantly around the memosphere. But things went wrong, especially at the famous 2005 trial where Judge John E. Jones III immortally summed up as “breathtaking inanity” the effort to introduce intelligent design into the school curriculum in Dover, Pa. After his humiliation in court, Behe — the star witness for the creationist side — might have wished to re-establish his scientific credentials and start over. Unfortunately, he had dug himself in too deep. He had to soldier on. “The Edge of Evolution” is the messy result, and it doesn’t make for attractive reading.

We now hear less about “irreducible complexity,” with good reason. In “Darwin’s Black Box,” Behe simply asserted without justification that particular biological structures (like the bacterial flagellum, the tiny propeller by which bacteria swim) needed all their parts to be in place before they would work, and therefore could not have evolved incrementally. This style of argument remains as unconvincing as when Darwin himself anticipated it. It commits the logical error of arguing by default. Two rival theories, A and B, are set up. Theory A explains loads of facts and is supported by mountains of evidence. Theory B has no supporting evidence, nor is any attempt made to find any. Now a single little fact is discovered, which A allegedly can’t explain. Without even asking whether B can explain it, the default conclusion is fallaciously drawn: B must be correct. Incidentally, further research usually reveals that A can explain the phenomenon after all: thus the biologist Kenneth R. Miller (a believing Christian who testified for the other side in the Dover trial) beautifully showed how the bacterial flagellar motor could evolve via known functional intermediates.

Behe correctly dissects the Darwinian theory into three parts: descent with modification, natural selection and mutation. Descent with modification gives him no problems, nor does natural selection. They are “trivial” and “modest” notions, respectively. Do his creationist fans know that Behe accepts as “trivial” the fact that we are African apes, cousins of monkeys, descended from fish?

The crucial passage in “The Edge of Evolution” is this: “By far the most critical aspect of Darwin’s multifaceted theory is the role of random mutation. Almost all of what is novel and important in Darwinian thought is concentrated in this third concept.”

What a bizarre thing to say! Leave aside the history: unacquainted with genetics, Darwin set no store by randomness. New variants might arise at random, or they might be acquired characteristics induced by food, for all Darwin knew. Far more important for Darwin was the nonrandom process whereby some survived but others perished. Natural selection is arguably the most momentous idea ever to occur to a human mind, because it — alone as far as we know — explains the elegant illusion of design that pervades the living kingdoms and explains, in passing, us. Whatever else it is, natural selection is not a “modest” idea, nor is descent with modification.

But let’s follow Behe down his solitary garden path and see where his overrating of random mutation leads him. He thinks there are not enough mutations to allow the full range of evolution we observe. There is an “edge,” beyond which God must step in to help. Selection of random mutation may explain the malarial parasite’s resistance to chloroquine, but only because such micro-organisms have huge populations and short life cycles. A fortiori, for Behe, evolution of large, complex creatures with smaller populations and longer generations will fail, starved of mutational raw materials.

If mutation, rather than selection, really limited evolutionary change, this should be true for artificial no less than natural selection. Domestic breeding relies upon exactly the same pool of mutational variation as natural selection. Now, if you sought an experimental test of Behe’s theory, what would you do? You’d take a wild species, say a wolf that hunts caribou by long pursuit, and apply selection experimentally to see if you could breed, say, a dogged little wolf that chivies rabbits underground: let’s call it a Jack Russell terrier. Or how about an adorable, fluffy pet wolf called, for the sake of argument, a Pekingese? Or a heavyset, thick-coated wolf, strong enough to carry a cask of brandy, that thrives in Alpine passes and might be named after one of them, the St. Bernard? Behe has to predict that you’d wait till hell freezes over, but the necessary mutations would not be forthcoming. Your wolves would stubbornly remain unchanged. Dogs are a mathematical impossibility.

Don’t evade the point by protesting that dog breeding is a form of intelligent design. It is (kind of), but Behe, having lost the argument over irreducible complexity, is now in his desperation making a completely different claim: that mutations are too rare to permit significant evolutionary change anyway. From Newfies to Yorkies, from Weimaraners to water spaniels, from Dalmatians to dachshunds, as I incredulously close this book I seem to hear mocking barks and deep, baying howls of derision from 500 breeds of dogs — every one descended from a timber wolf within a time frame so short as to seem, by geological standards, instantaneous.

If correct, Behe’s calculations would at a stroke confound generations of mathematical geneticists, who have repeatedly shown that evolutionary rates are not limited by mutation. Single-handedly, Behe is taking on Ronald Fisher, Sewall Wright, J. B. S. Haldane, Theodosius Dobzhansky, Richard Lewontin, John Maynard Smith and hundreds of their talented co-workers and intellectual descendants. Notwithstanding the inconvenient existence of dogs, cabbages and pouter pigeons, the entire corpus of mathematical genetics, from 1930 to today, is flat wrong. Michael Behe, the disowned biochemist of Lehigh University, is the only one who has done his sums right. You think?

The best way to find out is for Behe to submit a mathematical paper to The Journal of Theoretical Biology, say, or The American Naturalist, whose editors would send it to qualified referees. They might liken Behe’s error to the belief that you can’t win a game of cards unless you have a perfect hand. But, not to second-guess the referees, my point is that Behe, as is normal at the grotesquely ill-named Discovery Institute (a tax-free charity, would you believe?), where he is a senior fellow, has bypassed the peer-review procedure altogether, gone over the heads of the scientists he once aspired to number among his peers, and appealed directly to a public that — as he and his publisher know — is not qualified to rumble him.

Richard Dawkins a écrit :This style of argument remains as unconvincing as when Darwin himself anticipated it. It commits the logical error of arguing by default. Two rival theories, A and B, are set up. Theory A explains loads of facts and is supported by mountains of evidence. Theory B has no supporting evidence, nor is any attempt made to find any. Now a single little fact is discovered, which A allegedly can’t explain. Without even asking whether B can explain it, the default conclusion is fallaciously drawn: B must be correct

Incidentally, further research usually reveals that A can explain the phenomenon after all