Biochemical Complexity: Emergence or Design?

Biochemical Complexity: Emergence or Design? Bruce H. Weber In Darwin's Black Box: The Biochemical Challenge to Evolution, Michael Behe restates in modern biochemical terms William Paley's argument that there is an irreducible functional complexity to living beings that suggests the action of a designer-creator.1 He repeats Paley's challenge to science to provide a naturalistic explanation that can account robustly for such complexity and adaptation. Darwin responded to Paley's challenge by suggesting that the mechanism of natural selection acting upon random, heritable variation could account for biological adaptation and descent with modification. Behe argues that Darwin could not have known what we now know about organisms and lineages of organisms at the biochemical and molecular level. This knowledge, he claims, stretches the explanatory power of Darwinian conceptions to and beyond their limit, leaving us only the alternative of intelligent design to explain the emergence of novel and complex structures and phenomena in living systems. I wish to question whether biochemical complexity, as Behe represents it, is indeed irreducible and whether its emergence is beyond scientific scrutiny. Behe does not deny that natural selection can act on populations to cause changes in gene frequencies. Nor does he deny the occurrence of mutations. Indeed, he acknowledges that mutations in amino acid sequences of proteins provide evidence for descent with modification. To this extent Behe agrees that biochemistry supports the fact of evolutionary change. However, he sees the systems of proteins and enzymes involved in particular biological tasks, such as the bacterial flagellum, signal transduction at membranes, transport across membranes and within cells, blood clotting, the immune system, and the origin and regulation of metabolism as having too many components that have to interact in precise ways for such systems to have evolved by a piecemeal, gradual process like natural selection. It is not that a primitive eye or flagellum might not have a selective advantage but rather that to get even to such primitive structures would require a large number of molecular changes that would not have any functional value until all the minimal molecular Bruce H. Weber is Professor and Chair of the Department of Chemistry and Biochemistry at California State University in Fullerton, California. © Rhetoric & Public Affairs Vol. 1,No. 4,1998, pp. 611-616 ISSN 1094-8392 612 Rhetoric & Public Affairs components were in place. Therefore, the complexity of the biochemical examples Behe cites could not have arisen except by design any more than in the case of the mousetrap he uses as his analogy instead of Paley's watch, all other alternatives presumably being ruled out. He insinuates that this irreducible complexity is either ignored by contemporary evolutionists or is explained away by "just so" stories in order to protect the Darwinian paradigm. Behe makes much of the supposed lack of attempts by evolutionary biologists to provide credible causal explanations of the emergence of precisely such complex adaptive systems. Unfortunately, Behe does not give credit to what work has actually been done by the Darwinian research community . Further, he virtually ignores a whole area of current research on self-organizing , emergent phenomena. There have been many responses to Behe, some by biochemists, including one by myself,2 that address how adequately he has represented the current literature with regard to the specific examples he cites. There are in fact published attempts to address issues such as the origin of flagella, blood clotting, and the biochemical basis of vision, by invoking processes like gene duplication, domain and exon shuffling , and divergent evolution, all of which are suggested by current molecular data. Admittedly, this body of literature does not address how incomplete systems have selective advantage. But we are at the point of accumulating enough data from DNA sequences and three-dimensional structures of proteins to make a number of tests of putative evolutionary explanations in the near future. Behe, for example, argued that an account of the origin of the immune system is beyond the capacity of Darwinism, given its great complexity and the large number of genes required. The recent report, however, of the discovery of function of the RAG transposases and transposons in contemporary vertebrate immune systems, and reflections on the possible...