A while back, I summarized a review of the evolution of eyes across the whole of the metazoa — it doesn't matter whether we're looking at flies or jellyfish or salmon or shrimp, when you get right down to the biochemistry and cell biology of photoreception, the common ancestry of the visual system is apparent. Vision evolved in the pre-Cambrian, and we have all inherited the same basic machinery — since then, we've mainly been elaborating, refining, and randomly varying the structures that add functionality to the eye.
Now there's a new and wonderfully comprehensive review of the evolution of eyes in one specific lineage, the vertebrates. The message is that, once again, all the heavy lifting, the evolution of a muscled eyeball with a lens and retinal circuitry, was accomplished early, between 550 and 500 million years ago. Most of what biology has been doing since is tweaking — significant tweaking, I'm sure, but the differences between a lamprey eye and our eyes are in the details, not the overall structure.
Continue reading "Evolution of vertebrate eyes" (on Pharyngula)
What theory about the development of eyes do Wells and Dembski offer in their new IDC textbook? How do they explain the origins of the eye?
How do any IDC “theorists” explain the eye?
Don’t we already know? “The eye is too complex to arise randomly. The Designer did it.”
End of “discussion”. 8^(
We shall soon see ID creationists ignore or deny the evidence while failing to provide a competing explanation.
What a scientific sham ID truly is.
Wells and Dembski on the eye
As usual the authors seem to be presenting a good case for their ignorance of what science has to say about the evolution of the eye
Of course ask them how ID explains it and the response will likely be that ID is not up to the task.
This “God of the Gaps” BS is really getting tiring. It reminds me of the old (related) saying about Creationism:
“Identify a gap in the fossil record, then find a transitional form that perfectly fits in the gap, and a Creationist will conveniently respond that there are now two gaps!“
The eye is a perfect example of a form that looks intelligently designed at a glance, but a closer look totally demolishes that notion.
The vertebrate eye is wired backwards, with the optic nerve fibers on top of the cones and rods that act as light receptors. This makes no sense, and results a loosely attached retina that a sharp blow can detach easily and a blind spot that renders a part of the visual field useless. Only an idiot would have made such a rotten design. Which would explain why most Creationists seem to be idiots themselves!
Then there are the muscles of the human eye. There are six. A better design would have only three.
And what about the fact that many of us eventually need glasses and suffer from cateracts in old age?
The vertebrate eye is wired backwards, with the optic nerve fibers on top of the cones and rods that act as light receptors. This makes no sense, and results a loosely attached retina that a sharp blow can detach easily and a blind spot that renders a part of the visual field useless. Only an idiot would have made such a rotten design. Which would explain why most Creationists seem to be idiots themselves!
which is exactly why only cephalopods are intelligently designed (just check out the anatomy of THEIR eyes - no flaws), and the designer must be Cthulu or Dagon.
we’re just random flotsam on the evolutionary ladder cephalopods are gradually climbing before becoming masters of the universe.
PZ knows this, and not so subtly keeps hinting at it on his blog every friday.
That isn’t right. You’ve got three axes of rotation, and you need opposing pairs of muscles, so six pretty much is the optimum number…although you could make a case that rotating the eye about its central axis is not a necessary function, so the superior and inferior oblique muscles are a bit redundant.
[quote]although you could make a case that rotating the eye about its central axis is not a necessary function[/quote]
oh no, being able to roll my eyes at creobots is quite a necessary function.
hey, maybe that IS evidence of intelligent design?
:p
PZ says:
“…in the pre-Cambrian… (snip) …between 550 and 500 million years ago.”
One of the wonders of radiometric age determinations is that they allow us to learn that the Precambrian ended 542 million years ago. Thus the dates that you give above are mostly inconsistent with your Eon.
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