In this sequel to his bestselling book Darwin's Black Box, Discovery Institute senior fellow Michael Behe hones his argument for intelligent design (ID) by investigating the precise "edge of evolution." Behe's basic thesis is that Darwinian evolutionary processes can cause some changes in populations of living organisms, but they cannot cause all changes. Thus, there is an "edge," or limit, to the information generative power of Darwinian evolution. Controversial and timely, The Edge of Evolution presents landmark evidence that devastatingly disproves that the supposed evolution of cells to animals was largely a unguided Darwinian process.
Through a combination of experimental evidence, genome research, and mathematical law, Behe analyzes three key case studies of the tens of thousands of generations of malaria, E. coli, and the HIV virus, and the human genomic response to those invaders. We now know exactly what mutations have occurred in the struggle between these parasites and their human hosts. We know their rate of occurrence. We know all possible types of mutations, and their natural rate of occurrence. Armed with all this, it is a simple matter of extrapolation to determine the limits of Darwinian randomness in the entire tree of life on earth.
With The Edge of Evolution, intelligent design has the framework for a comprehensive scientific statement that draws the line between random and non-random mutation in nature; defines the principles by which Darwinian evolution can be distinguished from design; fits design theory together with the findings of cosmology, chemistry, and physics into an overarching theory of the universe; and lays out a research program, with predictions, to counter the failed predictions of Darwin's enthusiasts.
Behe goal is to investigate where the "edge" sits. He observes that neo-Darwinian evolution is very good at breaking or messing up biological systems, but it is not good at building new complex features that require multiple mutations to yield some functional advantage.
Many critics have badly misconstrued Behe's arguments in The Edge of Evolution. Contra critics, he readily allows that neo-Darwinian evolution can proceed forward when each successive mutation gives a selective advantage, writing:
[V]ariation, selection, and inheritance will only work if there is also a smooth evolutionary pathway leading from biological point A to biological point B. (p. 5)
However, when multiple mutations are required to yield some functional advantage, it is here that Behe proposes that Darwinian evolution will get stuck. The book discusses biological features that are beyond this "edge of evolution'."
For example Behe also elaborates on the idea of irreducible complexity, observing that in Darwin's Black Box he made the case for irreducible complexity based upon the structural features of molecular machines alone. While he still feels that argument is strong, he notes that when we consider the necessary assembly instructions required to build irreducibly complex molecular machines, we end up with "irreducible complexity squared." Behe thus writes:
How do Darwinists explain the cilium/IFT? In 1996, in Darwin’s Black Box I surveyed the scientific journals and showed that very few attempts had been made to explain how a cilium might have evolved in a Darwinian fashion—there were only a few attempts. 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 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. Despite the amazing advance of molecular biology as a whole, despite the sequencing of hundreds of entire genomes and other leaps in knowledge, despite the provocation of Darwin’s Black Box itself, in the more than ten years since I pointed it out the situation concerning missing Darwinian explanations for the evolution of the cilium is utterly unchanged. (pp. 94-95)
Critics also have tried to refute irreducible complexity with weak arguments which entail the mere observation that many proteins are similar, or share homology. Behe anticipates this objection in The Edge of Evolution, observing that, "modern Darwinists point to evidence of common descent and erroneously assume it to be evidence of the power of random mutation." (pg. 95).
The Edge of Evolution is an important contribution to the scientific debate over ID because it shows that the theory of ID gladly acknowledges that Darwinian evolution can produce some changes in populations. But it also shows that ID theorists have principled reasons for doubting that neo-Darwinian evolution can accomplish all that is claimed, and that there is a limit to the creative power of evolutionary processes. If Behe's thesis is correct, then that power is very limited indeed.