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Correcting the error in retinal design

I still remember how surprised I was as a medical student when I learnt that the mammalian eye is designed back to front. I thought I must have misunderstood. The fibres of the optic nerve are placed in front of the photoreceptors (rods and cones) instead of behind them, so that the light has to traverse the fibres before it reaches the light-sensitive area. This arrangement also produces the blind spot, where the optic nerve leaves the eye.

My surprise was of course based on a misunderstanding about evolution. Natural selection has no foresight and the structure of the eye wasn't planned; it was simply cobbled together bit by bit. According to today's New Scientist (8 May), however, the mammalian eye was later modified to compensate for this. The Müller cells support and nourish the overlying cells in the retina but also collect, filter and refocus the light to give a clearer image. So evolution first botched the design and then took steps to put things right.

What this puts me in mind of is the Hubble space telescope. Initially this was sent into space with a design fault, which had to be corrected later by a mission from earth. In that case there were of course human designers behind the telescope. If creationists wish to apply the same logic to the eye to infer the existence of a Creator they must also conclude that said Creator was as fallible as were the telescope designers. At most, this would be evidence, not for an omniscient Creator in the Christian sense, but for a Platonic demiurge - a superhuman being who did his best with what he found to hand but made a bit of a mess of things. The suggestion that this world is a computer simulation by a superhuman civilisation would also fit the facts for anyone who wishes to reject Darwinian natural selection.


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JOHN Floyd on :

Thank you again Anthony for providing me another talking point when in conversation the "amazing complexity of the human eye" is tossed out as a "proof" of intelligent design.

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