Defender's Guide to Science and Creationism

Assertion: The perfection of structures like the human eye is proof of creation.

Analysis

(i) Although well-adapted to its purposes, the human eye is imperfect. I am no longer sure whether the inversion of the vertebrate retina to be as severe a defect as I had thought before, but the fact that it produces a blind spot in the visual field of each eye where the neurons exit must be counted as an imperfection: surely an all-powerful designer whose crowning creation was man could have done better than that, whatever we think of the general efficiency of the eye.

The blind spot is, of course, not the only imperfection in the eye: it suffers from all of the normal afflictions of the human body: vulnerability to trauma, disease, and wear and tear. Were the eye perfectly designed, we should expect it to be more resistant to malfunction than it is. Remember, when we talk about a god, we are talking about a being whose power is unlimited, not even being constrained by the laws of nature; had such a being wished to make our eyes out of glowing ethereal quintessence (with no blind spots), there would have been nothing to stop him. Perhaps one might argue that the deficiencies of the eye, like the pain of childbirth, were the results of the Fall of Man, coming into being because of God's response to the disobedience of Adam and Eve; however, this is to acknowledge that things as we see them today are in fact imperfect, and thus takes away the evidence the assertion appeals to at the start.

Imperfect engineering is apparent in far more than the human eye, and extends beyond the vulnerabilities of flesh. Useless and inefficient structures that appear to be relics of distant ancestors abound in the natural world, such as the hollow bones of flightless birds, the clumsy "thumb" of the giant Panda, and the vestigial pelvis of pythons and whales (Futuyma 1983:198-200). If these things are the work of a creator, the creator apparently wants us to believe in evolution.

(ii) But imperfection aside, could biological structures as complex as the human eye, even admitting its imperfections, arise via evolution? Naturally, no one has observed the evolution of the eye in a laboratory because of the timescale involved, but one can look to the gradations in the present world for clues. In fact, nature displays progressions of simple to complex visual structures (Ecker 1990:65-66), such that one can see how the eye could have evolved gradually.

(iii) Paul R. Gross explains how a model by Dan Nilsson and Susanne Pelger has bolstered the case for the natural evolution of the eye by small steps:

In a 1994 theoretical paper, Nilsson and Pelger modeled one possible evolutionary pathway to the geometry of a fish-like eye from a patch of photo-responsive cells. There were already such cells — among the oldest organisms on Earth — a billion years before there were eyes. Nilsson and Pelger used pessimistic estimates of the relevant parameters (such as the intensity of selection) for their number-crunching. The point was to determine how many plausible, populational micro-steps of variation would be needed, under minimal assumptions, for very weak selection to yield a fish-like eye — and then under reasonable assumptions to convert micro-steps into generations and years. The order of magnitude answer was 350,000 — a geological blink of the eye. (Gross 2003)

There has been a strange controversy about the fact that some popular writings by Richard Dawkins (e.g. 1996: 161-165) describe Nilsson's and Pelger's work as a computer simulation, when it is in fact a mathematical model. Creationists appear to be very worked up about this, but as Nilsson himself explains:

I have not considered this to be very serious, because a simulation would be a mere automation of the logic in our paper. A complete simulation is thus of moderate scientific interest, although it would be useful from an educational point of view.

The Nilsson and Pelger (1994) paper remains scientifically sound, and it has not been challenged in any scientific journal with a peer review system. (Nilsson 2003)

We may regret Dawkins's lack of absolute precision, but the point is in the end a mere quibble, effecting none of the substance or importance of Nilsson's and Pelger's work.

References

Dawkins R. 1996. Climbing Mount Improbable. New York: W. W. Norton & Co.

Ecker EL. 1990. Dictionary of Science and Creationism. Buffalo: Prometheus.

Futuyma DJ. 1983. Science on Trial: The Case for Evolution. New York: Pantheon.

Gross PR. 2003. A scientific scandal. www.talkreason.org/articles/blurred.cfm#scandal.

Nilsson D-E. 2003. Beware of Pseudo-science: a response to David Berlinski's attack on my calculation of how long it takes for an eye to evolve. www.talkreason.org/articles/blurred.cfm#lund.

Defender's Guide to Science and Creationism
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