[extropy-chat] why the vertebrate eye might not be suboptimal after all

[Russell Wallace]

On 7/7/06, The Avantguardian <avantguardian2020 at yahoo.com> wrote:
>
> I agree with your friend, Damien. If ID were correct,
> you would think that humans would have the best eyes
> of all. We would have stable retinas with forward
> facing photoreceptors and no blind spot. We would have
> the night vision of cats, the distance vision of
> hawks, the polarized vision of squids, and the UV
> vision of honey bees, and a third transparent eyelid
> like birds.


While I don't know enough about the subject to know whether the advantages
of the current arrangement cited actually outweigh the disadvantages (though
I find it interesting that the matter appears to be debatable), there is a
long-standing tradition of criticizing the work of evolution; what is
interesting is that most of the time the error turns out to be on the part
of the critics. From the above list, for example: our night vision is
inferior to that of cats because (or at least partly because) the layer
behind the retina is black rather than reflective, but this cuts down on
glare in daylight; we could see UV if our lenses were transparent to it, but
the opacity is a feature rather than a bug, it helps protect the eye from UV
damage; and someone correct me if I'm wrong, but I believe hawks, while they
have superb distance vision, can't focus sharply on nearby objects. There
are always tradeoffs; neither evolution nor intelligent designers can
provide all possible features in a single design.

As it stands, we are lucky if we have
> 20/20 vision. I sure don't w/o corrective lenses.
>

Me neither. Since there is substantial variance among humans in visual
acuity, and I would have expected evolution to mop that up, here's a
question to which I'd be interested in the answer if anyone knows it:

Do populations which followed a hunter/gatherer lifestyle until recently
have the same variance in visual acuity as those which have been farming for
a few thousand years?
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