Would an infinite number of Darwinians, working at for an indefinite period of time, eventually prove a single instance of evolution producing a new species?
Philip Kitcher, a philosopher of science and committed Darwinian, confesses in his book, Living with Darwin, that if Darwinians "were to try experimenting on the natural selection of organisms with relatively long generation times it would take the lives of thousands of successive investigators to provide even the slightest chance of even the first steps toward experimental success." Living with Darwin, it turns out, takes a lot more commitment than most people realize.
Materialists do not accept an afterlife, of course, but they do believe in an infinite amount of time, and they surmise that given enough time, anything including life as we know it can happen. (Thus, it is famously postulated, infinite monkeys at infinite keyboards could produce the complete works of Shakespeare.) This argument runs into an empirical wall with the big bang, which limits the amount of time for life to develop to about 15 billion years. It also has the theoretical problem that long stretches of time do not make impossibilities more possible. A lot of time does make improbabilities more probable, but multiplying time does not guarantee that long sequences of improbabilities will actually occur.
Biology certainly has a lot to say about the role of luck in the evolution of life, but the question of how much luck evolution needs and how much luck nature provides to get the ball of life rolling has been as much a matter of philosophical and mathematical speculation as empirical observation. Only in the past few decades has the state of genetic research reached the point where an informed judgment about the probabilities presupposed by Darwinism can be made. Michael Behe's latest book, The Edge of Evolution, should establish the precedent for future debates. Darwinists will appeal Behe's verdict, no doubt, but for readers with an open mind, it will be hard to overturn.
Darwinists are imaginative when it comes to speculating about the possible pathways that connect the stages of evolutionary development. Behe demonstrates how these theoretical constructions run into too many roadblocks in the real world of genetics. Rather than demolish Darwinism, however, Behe wants to explore its limits. He acknowledges that scientists can follow the lineage of all creatures back to a common ancestor. He also acknowledges that Darwinian theory can account for some aspects of the development of new species. He just doesn't think that random mutation and natural selection are an exhaustively complete description of the path life has taken.
Behe's previous book, Darwin's Black Box, argued that some cases of design in nature are too elegant to have been produced by chance. His critics attacked him on two fronts. First, they suspected that his talk of intelligent design was merely a ruse for getting God back into public education. In other words, they impugned his motives, which is always a sign of rhetorical desperation. Even if his motives are suspect, his arguments should be examined on their own terms. Moreover, Behe is not afraid to offend all parties of the evolution debate. He accepts the common ancestry of chimps and humans, and he thinks there is no theological problem in imagining God working through the secondary causes posited by Darwin. Behe's position is hardly designed for easy use in the culture wars.
Second, his critics argued that intelligent design, whatever its merits, is not science. Even Behe's colleagues at Lehigh University, where he teaches, seem embarrassed by his position. The biology department mission statement on its website reads, "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." This is bad philosophy of science, if not poor collegiality, because many theories in science are not experimentally testable in any straightforward fashion. The role of luck in evolution is itself a matter of very abstract statistical debate.
Darwin's Black Box focused on specific cases of what he called irreducible complexity. Critics picked apart his examples like vultures on carrion. The Edge of Evolution more carefully and more comprehensively focuses on evolutionary processes at the level of molecular biology.
Much of this book tells the fascinating story of the epochal battle between the human and malarial genomes. Darwinians are fond of using the metaphor of an arms race to describe evolution. In an arms race, each side (predator and prey) responds to the other by improving their position, which means that their relative positions remain the same, even as their individual performances improve. Gazelles that run the fastest will pass more of their genes along to the next generation, for example, resulting in faster gazelles overall, but the lions that chase them will do the same thing. Darwinians use this metaphor to illustrate how species advance even as their role in the predator-prey scheme remains the same.
But what if the struggle of life looks more like trench warfare than an arms race? In trench warfare, anything goes for immediate gain. Species fight each other without any lasting improvements in their biological structures. "If the enemy can be stopped or slowed by burning your own bridges and bombing your own radio towers and oil refineries, then away they go. Darwinian trench warfare does not lead to progress it leads back to the Stone Age." This is exactly what happened in our attempt to disarm malaria. When chloroquine was first made widely available, it slowed down the spread of this tropical disease, but the malarial parasite soon evolved an effective defense against the drug. However, this battle did not result in a new and improved malarial cell. Instead, when chloroquine was no longer a threat, malaria reverted to its old ways. Its protective mutations deteriorated; they did not create anything new.
Behe admits that mutations can result in biological advances when organisms adapt to their environment by taking tiny, incremental steps. When larger steps are needed, however, evolution does not have a chance. Changes at the molecular level require long jumps that cannot be traversed by random mutations. Behe locates the limits of evolution in the length of these steps. "The more intermediate evolutionary steps that must be climbed to achieve some biological goal without reaping a net benefit, the more unlikely a Darwinian explanation." When organisms need to move forward in relatively brief time spans, they are more likely to stumble than advance. Or, as in the case of malaria, any successful step they take is just as likely to be followed by a step backward as by any forward progress.
Evolution is such a sensitive topic for the scientific community that Behe will be dismissed as a fringe thinker, but he does not think the edge of evolution is Darwin's undoing. Behe is a reformer, not a revolutionary. He wants to divide the Darwinian cake into small pieces so that he can be picky about what he accepts. Whether he has gotten to the bottom of Darwinism, he has shown that it lacks explanatory depth. Behe holds out the possibility that the progress of science, more than the claims of theologians, will undermine the dogmas of Darwin.
Stephen H. Webb is professor of religion and philosophy at Wabash College.
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Books & Culture also reviewed The Edge of Evolution.
Our recent coverage of intelligent design include:
ID Tagged | Faculty member at Iowa State University denied tenure for supporting intelligent design. (January 10, 2008)
Living with the Darwin Fish | Why the discovery of yet another 'missing link' doesn't destroy my faith. (March 12, 2007)