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Book Review: The Edge of Evolution: The Search for the Limits of Darwinism

By Fritz R. Ward

What in essence is Darwinian Evolution? Many philosophers would find that a fairly difficult question. For Daniel Dennett, it is a universal solvent that dissolves all non-materialist ideas. For some creationists, it is the root of much evil in the modern world, including racism, war, and a lack of compassion for the poor. For Kenneth Miller, a biologist at Brown University, it is an extraordinarily successful set of explanations for the diversity of life. But for Michael Behe, and one suspects many biologists, Darwinism is simply a series of propositions. These are 1) common descent of life, 2) natural selection (sometimes termed "survival of the fittest") and 3) random mutation at the cellular level driving the changes. The difference between Behe, an advocate of intelligent design, and Miller is simply one of the degree to which each thinks these propositions are applicable in describing life as we observe it. (Readers should note that Behe fully accepts common descent and natural selection. It is the random mutation mechanism that he has difficulty with.)

In this book Behe strikes off in a new direction from his previous work, Darwin's Black Box. Rather than simply explore cellular mechanisms that seem unlikely to arise from chance, Behe instead considers all the areas where evolution seems to function very well. For example, the rise of resistance among certain diseases, notably malaria, to synthetic drugs. Remarkable evolutionary pressures are at work in the struggle between humans and deadly pathogens. Humans who develop an immunity to malaria have a strong evolutionary advantage over those who don't. Similarly, protozoan parasites which can avoid the drugs we use to combat them also have an evolutionary advantage. Indeed, this is common knowledge among all biologists and most of the literate public. Germ resistance of all kinds to drug treatments is the star example of evolution at work.

But what is not so commonly known is that random mutation has severe limits in how effectively it can cope with evolutionary pressure. Indeed, what Behe demonstrates in precise detail is that evolutionary mechanisms are for the most part destructive: a part of the DNA stand is destroyed or replaced with a less efficient coding and the result is a weaker organism, though one which can survive the "trench warfare" of survival with hostile organisms. Thus, for example, humans have developed sickle cell anemia to cope with malaria. This is hardly beneficial, in and of itself, but compared to malarial death, it is a very helpful mutation. Similarly, malaria can rapidly evolve resistance to some drugs, slowly to others (more changes are required, and hence far fewer resistant copies of the cell are likely) but the mutated genes that come from this battle for survival are not optimal. Indeed, like sickle cell anemia, they rapidly die out of the malarial population if not subjected to the pressure of deadly (for the parasite) toxins in the form of antimalarial drugs.

So, while malaria (and several other cases Behe examines) suggests the efficacy of random mutation, it also suggests limits to just how much it can accomplish. Indeed, Behe finds that even two or three simultaneous random changes in DNA sequencing is exceedingly unlikely, and more just about impossible. This is very important because it suggests real limits to the amount of random mutation that could happen among higher mammals. People mistakenly believe that time is the most important factor in allowing for evolutionary change but as Behe demonstrates, population, not time, is what determines successful mutations. Malaria, and even more so HIV are extraordinarily effective at utilizing evolution. There are a lot of such organisms and they reproduce quickly. Humans, and indeed, all vertebrate and most invertebrate animals, do not. Even given the entire history of life on the planet, it is extremely unlikely that the random mutation proposition of evolution could account for a significant amount of the diversity we witness in the world around us.

Indeed, the situation is even worse than that according to Behe, because the mutations we actually observe in nature are almost always destructive or at a very minimum, sub optimal. They do not build up new structures. Despite strong evolutionary pressure, neither malarial protozoa nor HIV and similar retroviruses have ever developed a single new cellular structure. Indeed, as Behe tellingly notes, "Until an organism is found that is demonstrated to be much more adept than the malarial parasite at building coherent molecular machinery by random mutation and natural selection, there is no positive reason to believe it can be done. And the best evidence we have from malaria and HIV argues it is biologically unreasonable to think so."(p.155)

So if random mutation does not facilitate change in species, what does? For Behe the answer is clear: non-random mutation. But what causes that? One possibility, of course, is chance. A variant of this possibility is favored by physicists who believe in a multiverse. We are just extraordinarily lucky to have life here, but it looks designed to us. Aside from the fact that there is no evidence for a multiverse, there are logical problems with this solution to the problem of life and the forms it takes on earth. Behe discusses these and then moves on to more serious territory. Should we examine the possibility of a natural law that guides the evolutionary processes of natural selection leading to common descent? In and of itself, Behe finds this approach unappealing. Instead he advocates intelligent design, but in my opinion, especially as described by Behe, this is pretty much indistinguishable from such a natural law. Indeed, many of the natural laws in our universe are at present only explained by the anthropic principle and it is hard to imagine that this one would be any different.

Ultimately, of course, Behe moves from science proper (what we can infer from actual observations of evolution--namely random mutation is insufficient to explain common descent) to more philosophical speculations. What would the designer(s) be like? Can we infer anything about motive? What about the problem of evil? After all, any designer who might have "pre-programed" the possibility of intelligent life into the universe, say us, must also be responsible for malaria as well. These are serious issues and Behe is right to raise them. His critics will no doubt hammer him for it. These speculation are not "scientific" but that doesn't mean they are inappropriate. I think Behe is right when he notes that knowledge need not respect the boundaries we set for it in modern universities. Just because a topic does not yield to scientific inquiry hardly makes it unfit for all inquiry. Moreover, considering other questions will hardly invalidate the scientific portion of Behe's book or the considerable math behind it.

In my opinion this final chapter, where Behe takes on these philosophical questions, is the most important part of the book. It is also the most controversial. Readers will probably come to different conclusions, but Behe's ideas deserve serious consideration. As for the rest of the book, it lives up to its title. There is a clear edge or limit beyond which evolution is a poor mechanism for understanding life on the planet. That line may not be precisely where Behe claims it is, and future research will undoubtedly refine this edge further. But to persist in maintaining no such line exists requires at this point faith. Indeed, the next time a critic of ID suggests that scholars like Behe should be ignored because "they" are religiously motivated, readers would do well to remember that Freud, like Darwin, is largely discredited. But his theory of projection is still valid, much as Darwin's observations still apply to bacteria and antibiotics. Indeed, I predict such projections will figure very prominently in some reviews of this book. Those with an ideological axe to grind will not appreciate it. Thoughtful readers, on the other hand, will be fascinated with this excellent book.

(This review is reprinted with permission of the author)