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Thursday, July 12, 2007

2. The Edge of Evolution: What exactly does Behe say about Darwinism?

Not surprisingly, the science press greeted The Edge of Evolution with orchestrated hostile reviews.

Because Behe's actual thesis is apt to get lost amid the smoke, noise, and mirrors these reviews have generated, I am going to take a moment to outline it briefly:

In Darwin's Black Box, Behe was concerned to show that some elegant structures in life are beyond the reach of random mutation and natural selection (= Darwinism). In The Edge of Evolution , he seeks to draw up "reasonable, general guidelines" to determine where the edge of evolution is, "to decide with some precision beyond what point Darwinian explanations are unlikely to be adequate, not just for some particular structures but for general features of life." (8)

Darwinian evolution must be evaluated at the molecular level because that is the level at which the exact causes of a given change can be known. Recent technological advances have given us the tools to do that (10).

He studies in detail a number of cases where Darwinian evolution is known to have occurred. That is, the exact mechanisms of the changes that took place in the malaria parasite, E. coli, and HIV have been identified, and the change appears to have been caused by natural selection acting on random mutations. The vast numbers and the swiftness with which these microorganisms reproduce enable a rate of evolution that is equivalent to millions of years of evolutionary time for larger organisms. Thus, an estimate of the limits of Darwinian change is possible.

Characterizing the available evidence, Behe's metaphor for the relationship between the human immune system and the malaria parasite is destructive trench warfare, rather than the productive arms race beloved of Darwinist writers (19). For example, random mutations like sickle hemoglobin that confer protection from malaria always come at a cost: "Some are worse than others, but all are diminishments; none are constructive. Like sickle hemoglobin, they are all acts of desperation to stave off an invader." (38).

For that matter, the intestinal parasite E. coli, subject of the most extensive laboratory evolution study ever, evolved over thirty thousand generations mainly by devolving - throwing away sophisticated machinery, not by building it. (16)

Meanwhile, the malaria parasite, which can develop resistance to laboratory drugs within weeks, has not evolved resistance to the human sickle cell trait in thousands of years. That, Behe suggests, may point us to the limits of evolution by random mutation. (53) (Natural selection can be activated only when a mutation has occurred.)

In general, he suggests, two simultaneous mutations that create an advantage (like resistance to the antimalarial chloroquine) is a vastly higher hurdle for the malaria parasite to achieve via Darwinian evolution (59) than only one, on the order of 10 to the 20th power.

The significance of this figure becomes evident when we consider the fact that there have been so many fewer humans in the world than malaria parasites. If the rate of change is the same as observed in the lab, Behe notes: "No mutation that is of the same complexity as chloroquine resistance in malaria arose by Darwinian evolution in the line leading to humans in the past ten million years." (61) (Note: Behe is NOT claiming that no evolution occurred. He is saying that an evolutionary process cannot, on the evidence, have been a Darwinian one; it must have been nonrandom (83).)

Darwinian evolution depends on processes that break things rather than processes that create them: "... mutations that help in trench warfare by breaking something will appear at a rate hundreds of times faster than ones that help by doing something new." (69) As the example of freeze-tolerant fish shows, it is far more likely to occur among simple proteins than complex, machine-like ones (82). In the face of challenges that can only be addressed by reengineering, Darwinian evolution just stops. For example, the malaria parasite has never evolved a way to infest humans in cooler climates or get around sickled cells. (82)

Noting that in the long war between humans and malaria, neither side seems to have evolved new protein interactions (136-37), he argues that "complexes of just three or more different proteins are beyond the edge of evolution", but that the great majority of proteins in the cell work in complexes of six or more. (135) Similarly, the HIV virus has undergone no significant basic biochemical changes, despite its endless mutations in pursuit of resistance (139), nor has E. Coli (142) done so.

Behe calculates that, based on the available evidence of observed Darwinian mutations, events less likely than ten to the twentieth power are generally beyond the edge of (Darwinian) evolution (145).

There is the main argument in a nutshell, minus the supporting material. Many people, of course, will feel the need to argue for or against the thesis of The Edge of Evolution without bothering to read it. Despite the fact that it is very clearly written - a masterpiece of simple explanation, accessible to anyone who can read National Geographic or Scientific American.

Also worth noting:

- Both in The Edge of Evolution and in his previous book, Darwin's Black Box, Behe makes clear that he has no quarrel with common ancestry (page 12). Indeed, it is crucial to his thesis. In The Edge of Evolution, he also offers a defense of the common ancestry of human and chimpanzee (pp. 70-73).

- Contrary to claims heard recently, Behe discusses his earlier thesis of irreducible complexity at considerable length (86ff and 120ff) in EoE, explaining the challenge that structures such as the cilium/flagellum pose to Darwinian evolution. For example:
Although Brown University biologist Kenneth Miller argued in response that the two-hundred component cilium is not really irreducibly complex, he offered no Darwinian explanation for the step-by-step origin of the cilium. Miller's professional field, however, is the study of the structure and function of biological membranes, and his rejoinder appeared in a trade book, not in the scientific literature. An updated search of the science journals, where experts in the field publish their work, again shows no serious progress on a Darwinian explanation for the ultracomplex cilium. (95)


And what about the reviews? Well, they seem to be doing their best to discourage readers from actually reading the book. Having read it, I think I know why.

Next: The response to Edge of Evolution Dogs, Dover, Darwinists, and Deals


If you like this blog, check out my book on the intelligent design controversy, By Design or by Chance?, or my book of essays on faith and science topics, Faith@Science: Why science needs faith in the 21st century (Winnipeg: J. Gordon Shillingford, 2001). You can read excerpts as well.

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