From the issue dated December 21, 2001
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Seeking the Deity in the Details
Most scientists discount the idea of supernaturally directed evolutionBy RICHARD MONASTERSKY Since the 17th century, philosophers have been finding signs of divinity hidden within nature,
Known by the shorthand "ID," the concept drew scant attention from biologists for several years, until it became clear that the design movement was selling books and attracting attention as a more scientifically sophisticated alternative to biblical creationism. Now evolutionary scientists are starting to fight back, debating the ID proponents and writing their own books in response. "It always takes a while for the scientific community to respond to critiques of scientific work for the very simple reason that scientists don't always know whether to take them seriously," says Kenneth R. Miller, a professor of biology at Brown University and the author of Finding Darwin's God: A Scientist's Search for Common Ground Between God and Evolution, which counters many of the arguments put forward by supporters of intelligent design. The concept of intelligent design holds that the evolutionary process envisioned by Darwin and expanded by subsequent researchers cannot possibly account for the intricacies of life, from the clotting of blood to the way bacteria propel themselves through fluids. Instead, ID adherents argue that biological systems bear the hallmark of some intelligent entity who designed the molecular machinery of living cells in much the same way that humans build cars or other complex equipment. "We've discovered great complexity at the molecular basis of life," says Michael J. Behe, a professor of biological sciences at Lehigh University and one of the chief advocates of intelligent design. "You have molecular machines in the cell, which require many different components to work, and without one or more of the components, the systems would fail. And it's very difficult to see how something like this would be approached gradually, as Darwin envisioned." Mr. Behe's 1996 book, Darwin's Black Box: The Biochemical Challenge to Evolution, gave the design movement a big boost by offering specific examples of what he termed "irreducibly complex" systems inside cells. He uses an analogy of a mousetrap. Take away the spring or the lever that holds the bait, and the trap is worthless, he says. Such a realization makes it difficult to see how complex biological proc-esses could have evolved by adding one piece gradually onto other pieces, according to his argument. Bacterial Outboard Motors As a favorite example, Mr. Behe (pronounced BEE-hee) cites the whip-tail propulsion system used by some bacteria. Called the flagellum, it resembles an outboard motor, with elements that correspond to a propeller and others to an engine. Composed of some 50 proteins, the flagellum is irreducibly complex, says Mr. Behe, because "without parts of the various components, the motor would simply not work. It's not that it would work more slowly -- it wouldn't work at all." That property makes it a thorn in Darwin's side, followers of intelligent design assert. Mr. Behe and many other advocates of ID don't deny that evolution occurs, but he takes issue with the specific type of evolution accepted by most scientists today. According to modern evolutionary theory, species change through time because random mutations pop up in the gene pool, which gives individuals different traits. Some of those traits make certain individuals better suited to their environment, so they can propagate more readily and pass on the advantageous characteristics to their descendants. In that way, nature "selects" the winners from the lottery of individuals with different traits. Scientists since Darwin have realized that natural selection is not the only engine for change because, for instance, organisms can develop new traits that neither help nor hurt them in a specific context. But natural selection is the only way that organisms can end up becoming better adapted to their environments. Mr. Behe, however, argues that natural selection cannot explain the appearance of the flagellum because the proc-ess confers an advantage only after the motor is complete. What good is a half-finished motor to a bacterium? he asks. Instead of invoking natural selection, he says, it seems far more plausible that an intelligent force created the flagellum as a fully functioning unit. In his book, he goes on to call the recognition of ID a "result so unambiguous and so significant that it must be ranked as one of the greatest achievements in the history of science. The discovery rivals those of Newton and Einstein, Lavoisier and Schrödinger, Pasteur and Darwin." But Brown's Mr. Miller contends that the ID argument completely misunderstands how Darwinian evolution works. The various parts of the flagellum weren't destined to serve together as a motor when they first appeared piecemeal in the deep history of bacteria. Instead, the parts served different and separate purposes originally. Only later did they happen to come together to form a motor. Remnants of that process are still visible today in various lines of bacteria, he says. Yersinia pestis, the species that causes bubonic plague, produces a complex structure with 10 proteins closely related to the ones found in bacterial flagella. The deadly bug doesn't use those proteins to move; instead, they help Y. pestis inject its toxins into the cells of its host. Drawing on Mr. Behe's favorite analogy, Mr. Miller says that the various parts of a mousetrap have uses even on their own. Three out of the five components form a handy tie clip. Two of the five can serve as a clipboard. Nature is opportunistic, he says, cobbling together different molecules and reactions for entirely new purposes. How to Track the Transcendent The supporters of ID remain undaunted, however, saying that other evidence supports their cause. Many place great hope in the mathematical ideas of William A. Dembski, an associate research professor in the conceptual foundations of science at Baylor University. Mr. Dembski has developed an algorithm he calls the "explanatory filter" for detecting design in anything, both inside and outside of biology. For instance, it could help detectives determine if a death was accidental or intentional, he says. To explain any particular event or object, the explanatory filter first seeks to determine whether a predictable proc-ess is the cause. If statistical techniques suggest not, the filter asks whether the event occurred simply because of chance. If the probabilities argue against chance, then the event must have been caused, on purpose, by some designer, according to Mr. Dembski, who laid out the arguments in his 1998 book, The Design Inference: Eliminating Chance Through Small Probabilities. He is now starting to apply the technique to molecular systems to see whether evolution by natural selection could plausibly form such systems. So far, he says, Darwin isn't coming up a winner. "The Darwinian mechanism cannot do the design work in biology that biologists attribute to it," says Mr. Dembski. 'The Big G' Although he agrees with biblical creationists on some issues, Mr. Dembski differs on other ideas. Like Mr. Behe, he accepts that the world is much older than the 6,000 years consistent with biblical references and that organisms have all evolved from a common ancestor deep in earth's history. And he grants that Darwinian mechanisms can account for some minor evolutionary changes, such as insects' developing resistance to pesticides. "But natural selection and random mutation have limited power," he says. "The mechanism isn't sufficient to account for how you got insects in the first place." Intelligent-design proponents often avoid discussing the nature of the "intelligent designer," but Mr. Dembski says that many people draw the obvious connection. "Who or what is that intelligence? Within Western culture, it's not a big leap to get to the big G." Mr. Dembski's critics, however, view his whole approach as a leap of faith. Elliott R. Sober, a professor of philosophy at the University of Wisconsin at Madison, and his colleagues there called Mr. Dembski's work "deeply flawed" when they published a critique of his book in the journal Philosophy of Science. The main problem with the explanatory filter, says Mr. Sober, is that it claims to rule out all possible natural explanations for an event, even discounting theories that scientists have yet to discover. "There's no way you can test hypotheses that have not been stated ... no method can do that." He calls it unscientific because the filter can end up finding proof of design without requiring the design hypothesis to make any predictions. The ID proponents "have no theory that makes any predictions," he says, and testing predictions is a critical part of the scientific process. Norman R. Pace, a professor of molecular, cellular, and developmental biology at the University of Colorado at Boulder, is even blunter about the ID argument and its take on as-yet-unexplained aspects of biology. "It's bullshit. It's just more of the same. Namely we can't explain this, so there must be some sentient being that's put it into place. It's just the same reason that the cave folks who saw lightning said, 'Whoa! We don't know where that came from. It must be the gods throwing stuff at us.' " Mr. Dembski responds that "an argument from ignorance is still better than a pipe dream in which you're deluding yourself. I'm at least admitting to ignorance as opposed to pretending that you've solved the problem when you haven't." But he admits that ID has far to go. "I'm an ambitious man, and I'd like to see design prove itself at all levels and become the dominant paradigm. For that to happen, it's got to offer more than just a way of framing problems." And if intelligent design is going to win broader support, it must out-compete standard evolutionary theory in the hostile realm of scientific discourse -- where ideas are judged not by their popularity but by their explanatory power. In that world, only the fittest concepts survive. http://chronicle.com Section: The Faculty Page: A10
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Copyright © 2001 by The Chronicle of Higher Education