As a public skeptic of the ability of Darwinian processes to account for complex cellular systems and a proponent of the hypothesis of intelligent design (1), I often encounter a rebuttal that can be paraphrased as "no designer would have done it that way." A classic example is the backwards wiring of the vertebrate eye (2). If no intelligent designer would have done it that way, the reasoning goes, then a blind, purposeless mechanism must be responsible, with natural selection being the prime candidate. This is a negative argument, reaching its conclusion in favor of the sufficiency of unintelligent processes by ruling out intelligence, which depends critically on our ability to differentiate useless from functional features. That ability has been severely called into question by the recent work of Hirotsune et al (3).
The modern molecular example of poor design is pseudogenes. Why litter a genome with useless, broken copies of functional genes? It looks just like the aftermath of a blind, wasteful process. No designer would have done it that way (2). Yet Hirotsune et al (3) show that at least one pseudogene has a function. If at least some pseudogenes have unsuspected functions, however, might not other biological features that strike us as odd also have functions we have not yet discovered? Might even the backwards wiring of the vertebrate eye serve some useful purpose?
The peril of negative arguments is that they may rest on our lack of knowledge, rather than on positive results. The contention that unintelligent processes can account for complex biological functions should, to the extent possible, be supported by positive results, rather than by intuitions of what no designer would do. Hirotsune et al's (3) work has forcefully shown that our intuitions about what is functionless in biology are not to be trusted.
Michael J. Behe
(1) Behe, M. J. Darwin's Black Box: The biochemical challenge to evolution. The Free Press, New York (1996).
(2) Miller, K. R. Life's Grand Design. Technology Review 97, 24-32 (1994).
(3) Hirotsune, S. et al. An expressed pseudogene regulates the messenger-RNA stability of its homologous coding gene. Nature 423, 91-96 (2003).