>You wrote, "Perhaps you could say what it is about the trilobite eye that
>makes it a
>good example of this intelligent design business." First, it is irreducibly
>complex. Remove one of the lens, or the Huygen's curved interface between
>them, and the sharp focus is lost. Second, AFAIK there is no physical or
>chemical or biological law, or combination of them, that can account for the
>formation of the biconvexity.
Although the good focus is lost by loss of the full structure, the overall
function is not. I can still see some things without my glasses, even
though badly blurry. An improved focus is obviously adaptive, and I
believe that any one of the innovations would improve vision on its own.
Thus, the irreducibility of the complexity seems highly suspect. I do not
know details of trilobite eye evolution, so I am not certain about the
quality of other trilobite eyes besides the full biconvex lenses except for
the several kinds that are blind. Increasing variety of predators would
have provided a major incentive for improved eyes and thus selective
pressure. With Trilobitomorpha extinct, determining the genetic controls
seems unlikely.
Incidentally, there is yet another aspect to the complexity of trilobite
eyes. The crystal orientation must be just right to avoid double vision.
If you have ever seen Iceland spar in a geology text or museum, you may
remember that looking through the clear crystal produces a double image
along two axes. Only the third gives a single picture. Biological
structures frequently have oriented crystal structure, but I believe no
other arthropod has achieved the proper alignment.
Thus, trilobite eyes are certainly complex and not fully explained
evolutionarily, but to me not obviously inexplicable in the long run. An
evolutionary explanation should not detract from appreciating them as
wonders of creation, however.
David C.
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