What Mike said (as usual)!
Also a few thoughts, possibly somewhat off topic:
The nature of water and of what we call visible light, and later of air, had a great deal to do with it too. Consider:Water
and air actually absorb wide ranges of wavelengths, but both of them
have a broad "window" of transparency around the range of wavelengths to
which our eyes are sensitive. Our own vision cuts off a little short of
the ultraviolet, which some birds and insects for example can see, and
some eyes can see further into the infrared then we can. But generally
our window of visible wavelengths matches that of the transparency of
water and air pretty well. (Bear in mind that the air that we breathe is
generally pretty moist as well.)
This suggests that once we
start genetic engineering to produce Homo superior, one of the first
things we shall do well be to add another octave of visible wavelengths
at either end of the limits to our vision. While we are at it we had
better add bigger, and possibly more, eyes, together with the necessary
mental equipment for exploiting them.
Now, notice a few conservative notes to what I said:For
one thing, while I was at it, why not go all the way to x-rays at one
extreme and short waves at the other? There would be fascinating and
useful things to see and all points of that spectrum. I am reliably
informed that Superman, for one, can in fact see in all those
wavelengths and in fact x-rays as well.
It is not fully
impossible, but the organs we would need would not be our eyes. For most
of the range they would not resemble eyes at all. Consider infrared.
The most sophisticated infrared eyes that I can think of offhand are the
pits of pit vipers such as rattlesnakes. They behave more like pinhole
cameras than eyes. Also, they work best at close range when the snake is
cold and the prey is warm. They do not form a clear image. It is in
fact possible in principle to form better images in infrared than the
best that snakes can do, but it probably would take tens of millions of
years of selection to achieve major evolutionary breakthroughs to do so
through natural selection. For mammals to do so would be more demanding.
We produce a great deal of infrared fog ourselves. One reason we can
see so conveniently in what we call visible light is the fact that our
bodies do not produce visual noise in those wavelengths.
Another
reason is that visible light behaves well with lenses of materials and
sizes that our bodies can produce precisely and efficiently. This is
less true for most of the wavelengths that we miss.
Not to
make too much of a meal of it, nor to generalise too strongly, the
mechanisms of our eyes reflect the medium in which we live, the
available light in our environment, and the range of contiguous
wavelengths that efficiently form images in the materials that our
bodies can produce and manage.
There also is the question of
"evolutionary opportunism", the options open to natural selection for
producing different kinds of eyes. This is a very difficult thing to do.
It looks suspiciously as though all the rhodopsin-based (basically, pigment-based) eyes in nature
stem from a single ancestral development, whether the eyes of worms, clams, spiders or humans. That is a very sobering thing to
consider. If we want to make major strides in improving our vision,
then natural selection will not be the appropriate route.