According to the enthusiasts for ID, metabolic systems, such as the clotting cascade, are too complex ("irreducibly complex" in their preferred wording) to have arisen through evolution.2 Problems with this view are readily apparent. First, complexity is problematic to define, and irreducible complexity more so.
At present, it is doubtful whether it is possible to measure, prospectively and precisely, the complexity of biological systems so as to distinguish systems that are irreducibly complex from those that are reducibly complex. The concept of irreducible complexity is simply asserted; it is not based on either evidence or compelling logic. Consequently, proponents of ID must decide, essentially arbitrarily, what is too complex to have evolved. They can claim that all of life is too complex to have evolved. Or, are we to believe that bacteria evolved but that humans (or mammals, or whatever groups of organisms) were designed? Would it make any more sense the other way around?
A truly fundamental problem with the notion of ID, as a scientific idea, is that, ultimately, it has effectively no explanatory or predictive power. Suggesting that an unknown Intelligent Designer of unspecified attributes designed the eye, the clotting cascade, or the immune system offers no scientific insights into these biologic marvels and suggests no incisive experiments. There is also the nagging issue of how the Intelligent Designer implements designs without being noticed. How do ID proponents explain the existence of defective genes, no longer capable of expression, in one species that are strikingly similar to still functional genes in a related species? What insights does ID provide in accounting for the origin and spread of bacterial resistance to antibiotics? These phenomena are consistent with the principles of evolution, which find application from the molecular level to the level of ecosystems.
Were the genes associated with conditions such as sickle cell disease or cystic fibrosis designed by The Intelligent Designer, or by her sister, The Not-So-Intelligent Designer? If the response is that we do not understand the motives or goals of the Designer, then of what use is it to posit this inscrutable being in explaining such realities as the relatively high frequencies of these genes in the human population.
On the other hand, evolutionary principles provide a compelling rationale for the high prevalence of the b-globin allele associated with sickle cell disease: in a single copy it provides protection from the deadliest effects of one type of malaria parasite. Consistent with this hypothesis, sickle cell disease is prevalent almost exclusively in populations that live in, or are descended from those who lived in, malaria-endemic regions of the globe. Whereas some ID advocates suggest that mutations are uniformly harmful, there are thoroughly documented human mutations, such as the mutation associated with sickle cell disease, that are alternately harmful or beneficial depending on the exact genotype and the environmental circumstances.
Enthusiasts for ID ignore the growing laboratory evidence for the selection of biological function from random collections of proteins and nucleic acids.3,4 Molecular biologists and biotechnologists have shown that selection acting on randomly generated libraries of billions or trillions of biological polymers, such as peptides or RNA molecules, can produce molecules with useful biological functions, such as specificities for small ligands or catalytic activities. Computer scientists, complexity theorists, and even physical chemists have also documented striking examples of order that develops spontaneously.5,6 It is simply no longer tenable to equate order, complex structure, or sophisticated function uniquely with conscious design.
The Design advocates also ignore the accumulating examples of the reducibility of biological systems. As Russell Doolittle has noted in commenting on the writings of one ID advocate, mice genetically altered so that they lack either plasminogen or fibrinogen have the expected abnormal hemostatic phenotypes.7 However, when the separate knockout mice are bred, the double knockouts apparently have normal hemostasis (reducible complexity after all), at least in the laboratory.8 These results cast doubt on the claim by proponents of ID that they know which systems exhibit irreducible complexity and which do not.
Evolution is best regarded as a fact. What is more, it is a fact that is inescapable. The resistance of bacteria to overused antibiotics, viruses to inhibitors of viral replication, and insects to pesticides, are all examples of the evolutionary process in operation. If you do research with cells or microorganisms, genetic variation and selection are continuously in evidence, even when you would prefer them not to be. Thus, that evolution occurs, and has occurred, is not in doubt. It has been directly observed in operation not only in the laboratory but also in the field.9 Where there is still room for argument and discussion is in the precise contributions of different mechanisms to evolutionary change. In this vibrant debate, intelligent design offers no meaningful contribution.
The effort to insert nonscientific ideas into Ohio's science curriculum is being carried out under the banner of promoting critical thinking.10 Perhaps other scientists will be as surprised as I was to learn that the education bill, "No Child Left Behind," signed into law by President George W. Bush on Jan. 8, originally contained an amendment from US Sen. Rick Santorum (R-Pa.). This amendment, ultimately removed from the bill, comprises the following two statements: "It is the sense of the Senate that: (1) good science education should prepare students to distinguish the data or testable theories of science from philosophical or religious claims that are made in the name of science; and (2) where biological evolution is taught, the curriculum should help students to understand why the subject generates so much continuing controversy, and should prepare the students to be informed participants in public discussions regarding the subject."
It would appear that a new and clever strategy has been found to get religious ideas into biology class. Those in other states concerned that the science curriculum remains focused on science should be vigilant against similar campaigns in their own states. Otherwise, they could find that the officials crafting the science curriculum for their schools are engaged in a process that comes closer to deserving the label "subversive design" rather than "intelligent design."
1. J. Mangels, S. Stephens, "Evolution targeted in curriculum study," The Plain Dealer, Jan. 15, 2002, pp. A1, A9.
2. M.J. Behe, Darwin's black box: The biochemical challenge to evolution, New York: Free Press, 1997.
3. J.R. Lorsch, J.W. Szostak, "Chance and necessity in the selection of nucleic acid catalysts," Accounts of Chemical Research, 29:103-10, 1996.
4. J.K. Scott, G.P. Smith, "Searching for peptide ligands with an epitope library," Science, 249:386-90, 1990.
5. S.A. Kauffman, The origins of order: Self-organization and selection in evolution," New York: Oxford University Press, 1993.
6. D. Kestenbaum, "Gentle force of entropy bridges disciplines," Science, 279,1849, 1998.
7. R. F. Doolittle, R.F. "A delicate balance," Boston Review, February/March 1997, or online at bostonreview.mit.edu/br22.1/doolittle.html.
8. T.H. Bugge, "Loss of fibrinogen rescues mice from the pleiotropic effects of plasminogen deficiency," Cell, 87:709-19, 1996.
9. J. Weiner, The beak of the finch: A story of evolution in our time, New York: Alfred A. Knopf, 1994.
10. R. Lattimer, J. Calvert, "Intelligent design is a matter of academic freedom," The Plain Dealer, Jan. 18, 2002, p. B9.