Re: Why don't animals need glasses?

On Sep 30, 11:26 am, "Ralph" <nt_consultin...@xxxxxxxxx> wrote:
"Ron O" <rokim...@xxxxxxx> wrote in message

news:1191171352.843689.119780@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx





On Sep 30, 11:32 am, dkomo <dkomo...@xxxxxxxxxxx> wrote:
Actually, this is a teaser question brought on by ruminating on the idea
that if human beings had to rely on their eyesight to survive today, as
we did in our hunter gatherer days, our population numbers would be far
less than they are.

Here's an amazing fact:

"The global prevalence of refractive errors has been estimated from 800
million to 2.3 billion.[20] The incidence of myopia within sampled
population often varies with age, country, sex, race, ethnicity,
occupation, environment, and other factors.[10][21] Variability in
testing and data collection methods makes comparisons of prevalence and
progression difficult.[22]

In some areas, such as Japan, Singapore and Taiwan, up to 44% of the
adult population is myopic."

http://en.wikipedia.org/wiki/Myopia

What can explain the loss of good vision in our species? Presumbably at
one time vision must have been quite important to our survival, as we're
not gifted with keen hearing or smell as other animals are. If another
species which used to rely on vision to hunt or escape predators started
to develop vision problems as prevalent as ours, it might go extinct
because it would have no way to correct these problems like we do.

Do animals develop myopia? It's probably difficult to test for this.
I'm not aware of any experiments that have been done.

Possible explanations for the spread of human myopia:

1. Reading brings it on.

2. We don't need keen eyesight for hunting anymore, so mutations in
genes that control vision have caused a weakening of eyesight in our
species.

3. In prehistoric times, people with myopia would have been eliminated
from the population by natural selection. Nowadays, wearing glasses
allows people with myopia to lead normal lives and to have offsping,
causing genetic defects producing myopia to spread.

--dk...@xxxxxxxx

There could be environmental factors, but my first guess is that it is
like blind cave fish. Our eyesight only has to be good enough to
survive. Even for hunter gatherer bands there was likely a
distribution of labor. Nearsighted members might not be the best
hunters, but they could set snares, do close in gathering, baskets,
nets, etc. and close in detail work would suit them. These people
might not have been able to use a bow, but they could make one.

Eyes are expensive to maintain. A lot of traits have to be selected
for and against. There is slop in the system, but eyes are one of the
first things to go if they aren't needed.

Ron Okimoto

Yes. I believe those suffering from myopia in prehistoric days were called
vegetarians.

The reason is night lights and lack of visual variety during development.
Remember you heard it first here. <g>

-ralph

My eyesight was perfect until about age 17....I noticed that I could
not focus 100% on the blackboard in school if I was in the back row.
By the time I was 19, my vision was bad enough that I had to get
glasses to drive. The deterioration stopped by age 30 and now my
prescription is about -4.2 in both eyes.

I wonder if literacy rates have anything to do with it. We spend our
days focusing on things that are no more than a few feet away. If we
spent our days outside, focusing on items in the distance for a
significant portion of the day, I wonder if the need for glasses would
be reduced.

Ken

.

Relevant Pages

  • Re: Why dont animals need glasses?
    ... that if human beings had to rely on their eyesight to survive today, ... we did in our hunter gatherer days, our population numbers would be far ... allows people with myopia to lead normal lives and to have offsping, ... perhaps our modern genes give greater resistance to ...
    (talk.origins)
  • Re: Why dont animals need glasses?
    ... that if human beings had to rely on their eyesight to survive today, ... we did in our hunter gatherer days, our population numbers would be far ... one time vision must have been quite important to our survival, ... Nowadays, wearing glasses ...
    (talk.origins)
  • Re: Why dont animals need glasses?
    ... that if human beings had to rely on their eyesight to survive today, ... we did in our hunter gatherer days, our population numbers would be far ... What can explain the loss of good vision in our species? ... Do animals develop myopia? ...
    (talk.origins)
  • Re: Why dont animals need glasses?
    ... that if human beings had to rely on their eyesight to survive today, ... we did in our hunter gatherer days, our population numbers would be far ... one time vision must have been quite important to our survival, ... Nowadays, wearing glasses ...
    (talk.origins)
  • Re: Why dont animals need glasses?
    ... that if human beings had to rely on their eyesight to survive today, ... we did in our hunter gatherer days, our population numbers would be far ... What can explain the loss of good vision in our species? ... Do animals develop myopia? ...
    (talk.origins)