[ExI] what big eyes you have
pharos at gmail.com
Thu Jul 12 17:09:52 UTC 2012
On Thu, Jul 12, 2012 at 4:27 PM, spike wrote:
> Why do big beasts have big eyes? I get why small beasts have small eyes
> (packaging considerations) but human eyes are about the size of a ping pong
> ball and they seem to work fine; they can see close, they can see far.
> Eagles have smaller eyeballs than ours, but they work even better. So why
> don’t elephants and cows have ping pong ball sized eyes? I can’t think of
> any advantage to eyeballs scaling with the size of the beast, but I can
> think of some serious disadvantages, such as they would be more easily
> injured and would be more affected by gravity. Granted an elephant with
> little beady human eyes would look weird, but we would get used to it. So
> why didn’t evolution think of it by now?
'Cause it's not true. :)
As a general rule, eyes, like brains, (like pretty much every body
part) scale with body size.
But there are loads of exceptions.
Animal, insect, fish, etc. eyes are differently designed to human eyes
and optimised for different purposes.
Human eyes are more general purpose, like their brains.
If light-gathering is important, then animals have proportionally
bigger eyes. Owls, nocturnal rodents, deep sea animals, etc.
Eagle eyes only work better in one respect. Long distance focusing,
because they can focus both the lens and the cornea. Tiger Woods and
others had to get an eye op to improve their vision above normal.
(Now discuss penis and testicle size). :)
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