The Vexing Eye

David Berlinski
Commentary
February 12, 2003
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The following is an excerpt from David Berlinski's article "Has Darwin Met His Match? (Commentary, December 1, 2002).

IN 1994, Dan E. Nilsson and Suzanne Pilger published a paper in the Proceedings of the Royal Society entitled, "A Pessimistic Estimate of the Time Required for an Eye to Evolve." By "pessimistic," they meant an estimate that, if anything, exaggerated the length of time required for the eye's evolution. Even so, their conclusions were remarkable. "A light-sensitive patch," they wrote, "will gradually turn into a focused-lens eye" in only a few hundred thousand years.

Darwin had himself been troubled by the existence of the mammalian eye, whose evolution by random mutation and natural selection has always seemed difficult to imagine. Nilsson and Pilger's paper provided a welcome redemptive note. A few hundred thousand years and the job would be done. Authors have waited longer for their royalty checks.

As Nilsson and Pilger's paper gained currency, it amassed content it did not actually possess. Biologists who failed to read what Nilsson and Pilger had written--the great majority, apparently--assumed that they had constructed a computer simulation of the eye's evolution, a program that could frog-march those light-sensitive cells all the way to a functioning eye using nothing more than random variation and natural selection. (2) This would have been an impressive and important achievement, a vivid demonstration that Darwinian principles can create simulated biological artifacts.

But no such demonstration has been achieved, and none is in prospect. Nilsson and Pilger's computer simulation is a myth. In a private communication, Nilsson has indicated to me that the requisite simulation is in preparation; his assurances are a part of that large and generous family of promises of which "your check is in the mail" may be the outstanding example.

What Nilsson and Pilger in fact described was the evolution not of an eye but of an eyeball, and they described it using ordinary back-of-the envelope calculations. Far from demonstrating the emergence of a complicated biological structure, what they succeeded in showing was simply that an imaginary population of light-sensitive cells could be flogged relentlessly up a simple adaptive peak, a point never at issue because never in doubt.

Despite a good deal of research conducted over the last twenty years, the mammalian visual system is still poorly understood, and in large measure not understood at all. The eye acts as a focusing lens and as a transducer, changing visual signals to electrical ones. Within the brain and nervous system, complicated algorithms must come into play before such signals may be interpreted. And no theory has anything whatsoever of interest to say about the fact that the visual system terminates its activities in a visual experience, an episode of consciousness. We cannot characterize the most obvious fact about sight--that it involves seeing something.

These are again circumstances that properly afford a measure of satisfaction to members of the intelligent-design community. But in what respect is our understanding improved by assuming that the visual system is the result of intelligent design? Unless very specific religious hypotheses are invoked, neither the identity nor the nature of the designer is known. The principles that he employs are a mystery, and the objects of his design are not well understood. Certain questions now reappear with unyielding insistence. Could a designer whose nature we cannot fathom, using principles we cannot specify, construct a system we cannot characterize?

If the question is unyielding, so, too, is its answer: who knows?

DAVID BERLINSKI is a senior fellow of the Discovery Institute and the author of A Tour of the Calculus, The Advent of the Algorithm, and Newton's Gift. His new book,
The Secrets of the Vaulted Sky
, is forthcoming from Harcourt next year.