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Richard S. Norman rnorman at umich.edu
Thu Dec 12 16:29:26 EST 2002

On 12 Dec 2002 13:20:25 -0800, jmdrake_98 at yahoo.com (jmdrake) wrote:

>Jerry Avins <jya at ieee.org> wrote in message news:<3DF8929A.FD075AD4 at ieee.org>...
>> jmdrake wrote:
>> > 
>> >   ...  The extra layers
>> > of non-sensitive cells that the light must pass through before reaching
>> > the sensitive cells acts like a "filter" to protect from UV radiation.
>> > That's such a concern that human "engineers" have devised UV blocking
>> > sunglasses to further block potentially damaging rays.  
>> Those special UV-blocking lenses were invented not by engineers, but by
>> advertising copywriters. Uncoated glass lenses block harmful UV.
>> Coatings are needed only on plastic to bring them up to the standards
>> set by glass.
>Advertising copywriters typically don't invent anything.  
>> UV is also blocked from the retina by the vitreous humor. The greatest
>> danger UV poses to unprotected eyes is to the lens. Inverting the retina
>> can't help that. All the chordata have inverted retinas, including fish.
>UV can also damage the retina, especially in young children.
>With regards to fish that's irrelavent.  The argument isn't about fish
>versus celophods but man versus celophods.  Whether fellow sea creatures
>have different types of eyes neither adds no detracts from the
>evolutionary argument.  Actually nothing regarding celophod eyes
>really does anything for the evolution argument unless you wish to
>go with a "straw man" approach.
If you are trying to make an evolutionary argument, fish are certainly
relevant.  The human eye is the primate eye is the mammalian eye is
the tetrapod eye is the vertebrate eye.  There are all the same basic
design.  It was the fish who built it backwards!  (Well, not modern
fish, but aquatic chordates nonetheless.)

The cephalopod eye is simply an example of a complex, camera eye
that is build "properly", with the light first striking the receptor
cells.  It is used to demonstrate that, if there are two ways to do
something, nature will try both regarless of which is supposedly

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