Irreducible complexity (IC) is a pseudoscientific argument that certain biological systems cannot be evolved by successive, slight modifications to a functional precursor system through natural selection acting upon a series of advantageous naturally occurring chance mutations.
Michael Behe, a professor of biochemistry at Lehigh University, first argued that irreducible complexity made evolution purely through natural selection of random mutations impossible. However, evolutionary biologists have demonstrated how such systems could have evolved. There are many examples documented through comparative genomics showing that complex molecular systems are formed by the addition of components as revealed by different temporal origins of their proteins.
Behe’s analogy for why irreducible complexity proves “intelligent design” was simple: If one were to gaze upon Mt Rushmore, one would conclude that a sculptor – an “intelligent designer” – created the complex set of faces; these could not be due to natural wind and water erosion over time. Likewise, complex biological structures, such as the biochemical “motors” of bacterial flagella, are like little biochemical machines that should be interpreted the same way as are human-designed and -constructed machines, such as the outboard motor of a boat. Such features, according to Behe, are irreducibly complex – composed of many separate parts arranged so that if even one part were removed or altered, the structure would not work. Therefore, the separate and mutually interdependent parts must have been designed with a final purpose in mind; they could not have evolved as different and independent parts that fortuitously and ultimately worked together to form a functioning complex structure. This argument can, of course, be used with every biological feature, structure, and process, since all are complex and make use of interdependent and interacting parts, themselves exceedingly complex.
Behe’s suggestion that ID can be tested by taking flagella-less bacteria and growing them for thousands of generations to see if they evolve flagella without “intelligent” modification of their genes was superbly audacious, but deliberately deceptive. A proper test of ID would involve its making some prediction about a biological process, event, or feature that could not, in principle, be explained by evolution but only by “intelligent design”. Not only have there been no successful tests of ID reported in the scientific literature, there have been no tests of ID reported there at all, indicating the essentially nonscientific nature of the enterprise.
Behe also repeated the ID motto – the evidence shows design in living organisms, but “ID leaves the identity of the designer open”. His colleague William A Dembski also uses this disingenuous disclaimer, saying that ID research points to “generic design”, not necessarily supernatural design. It is scientifically (and epistemologically) absurd to accept these claims. Contrary to Behe and Dembski, there is no evidence for any true design in the structure of living organisms – in the sense of a purposeful planning of outcomes – but there is excellent and well-known evidence for natural selection as the cause of their apparent design.
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