Why don't animals need glasses?

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.


--dkomo@xxxxxxxx

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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 ... 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 ... 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, ... allows people with myopia to lead normal lives and to have offsping, ...
    (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, ... allows people with myopia to lead normal lives and to have offsping, ...
    (talk.origins)
  • Report on the Young Chinese Eye -- A Normal Refractive Status Change?
    ... working to "clear" your vision wearing a -2.0 diopter lens ... Subject: Myopia Increases Among Children ... elementary schools is myopic. ... "She brought the boy in and I examined his eyes. ...
    (sci.med.vision)