I am interested in the evolution of complex biochemical systems. Despite much progress by science in the past half century in understanding how such systems work, little progress has been made in explaining how they arise. A key issue is that many systems in the cell require multiple components in order to function. I have dubbed such systems “irreducibly complex” (IC). (Behe 1996) The problem that multi-component systems present to a gradualist Darwinian evolutionary framework has been apparent at least since 1871, when the English biologist St. George Mivart wrote of “The Incompetency of ‘Natural Selection’ to Account for the Incipient Stages of Useful Structures.” Put into modern parlance, the problem is that the function of an IC system only appears when the system is essentially complete, frustrating selection by small Darwinian steps.
(Figure 1. A simple illustration of the concept of irreducible complexity. The pictured mousetrap needs all of its parts to work.)
Yet, as formidable a barrier as irreducible complexity itself presents to undirected constructive evolution, research in just the past few decades has revealed an even greater, unexpected, independent difficulty. As the technology to sequence genes and genomes has become ever cheaper and faster, the identities of helpful, positively selected mutations have become ever easier to track down. As a result it has become ever clearer that the large majority of beneficial mutations degrade genes. I have summarized that tendency as “The First Rule of Adaptive Evolution”: Break or blunt any functional coded element whose loss would yield a net fitness gain.” (Behe 2010) Odd as it may seem given previous expectations, the Darwinian mechanism of random mutation and natural selection is actually powerfully de-volutionary, in the sense that it relentlessly degrades genetic information for short-term gain. And of course a strongly devolutionary process makes for quite the dubious candidate to build complex functional systems in the first place. I discuss the evidence for and implications of this phenomenon in a recent book, Darwin Devolves. (Behe 2019)
For several decades I have argued that a much more rationally justified explanation for IC systems is that they were deliberately designed by an intelligent agent (Behe 1996, 2001, 2004, 2007, 2019). Although it has proven to be extremely controversial (for just one example, see Brumfiel, G. 2005. Nature 434:1062-1065), the conclusion of intelligent design follows straightforwardly from the empirical data — that is, from the physical structures of biochemical systems — when applying the same elementary logical steps by which conclusions of design are drawn for ordinary non-biological systems (such as the mousetrap shown in Figure 1) — that is, by inductive reasoning about a purposeful arrangement of parts.
My arguments about irreducible complexity and intelligent design are my own, and are not endorsed either by Lehigh University in general or by the Department of Biological Sciences in particular.
- 1996. Darwin’s Black Box: The Biochemical Challenge to Evolution. Free Press, New York.
- 2000. Self-Organization and Irreducibly Complex Systems: A Reply to Shanks and Joplin. Philosophy of Science 67, 155-162.
- 2001. Reply to My Critics: A Response to Reviews of Darwin’s Black Box: The Biochemical Challenge to Evolution. Biology and Philosophy 16, 685-709.
- 2004. "Irreducible Complexity: Obstacle to Darwinian Evolution." In Debating Design: from Darwin to DNA, Ruse, M. and Dembski, W.A., eds., Cambridge University Press, pp. 352-370.
- 2007. The Edge of Evolution: The Search for the Limits of Darwinism. Free Press, New York.
- 2010. Experimental Evolution, Loss-of-Function Mutations, and ‘The First Rule of Adaptive Evolution.’ Quarterly Review of Biology 85, 419-445.
- 2019. Darwin Devolves: The New Science about DNA that Challenges Evolution. HarperOne, New York.
Behe, M. J. 2013. Getting There First: An Evolutionary Rate Advantage for Adaptive Loss-of-Function Mutations. Biological Information: New Perspectives, edited by R. J. Marks II, M. J. Behe, W. A. Dembski, and B. L. Gordon. World Scientific Publishing, Hong Kong, 450-473.
Behe, M.J. 2010. Experimental Evolution, Loss-of-Function Mutations, and ‘The First Rule of Adaptive Evolution.’ Quarterly Review of Biology 85, 419-445.
Behe M. J. 2007. The Edge of Evolution: the search for the limits of Darwinism. Free Press, New York.
Behe, M.J. 2005. Design for Living. New York Times, February 7, p. A21.
Behe M.J., Snoke D.W. 2004. Simulating evolution by gene duplication of protein features that require multiple amino acid residues. Protein Sci13:2651-2664.
Behe, M.J. 2003. "Design in the Details: The Origin of Biomolecular Machines." In Darwinism, Design & Public Education, Campbell, J.A. and Meyer, S.C. eds., Michigan State University Press, pp. 287-302.
Behe, M.J. 2003. "The Modern Intelligent Design Hypothesis: Breaking Rules." In God and Design: The Teleological Argument and Modern Science , Neil Manson, ed., Routledge, pp. 277-291.
Behe, M.J. 2002. The challenge of irreducible complexity. Natural History 111, 74.
Behe, M.J. 1999. Teach Evolution—And Ask Hard Questions. New York Times, August 13, p. A21.
Behe, M.J. 1996a. Darwin Under the Microscope, New York Times, October 29, p. A25.
Behe, M.J. 1996b. Darwin’s Black Box: The Biochemical Challenge to Evolution, The Free Press, New York.