Evolutionary question

[DarrenS]

Hi all,

Here’s something I’ve wondered about for a while. I’m a firm believer in Evolution but the following mystifies me.

As a “four eyes”, or “speccy twat” myself (for non Brits: mocking terms for people who wear glasses), I have wondered why Evolution hasn’t selected this characteristic out? You would think that someone like me would be at a bit of a disadvantage in the wilds - not being able to tell a bush from a tiger until it’s 2 feet away. Maybe because it’s not a genetic thing?

Anyone have any ideas?

-Darren.

[Surgoshan]

Gimme a minute to look it up, but I think one of Cecil’s articles implied or stated that reading hurts the eyes. That is, because we teach our children to read, it puts strain on the eyes and increases instances where people need to wear glasses. That is, nurture over nature.

[Surgoshan]

Okay, after multiple searches, I’ve failed to find it. I think someone was asking about glasses or something. Sigh. I’m a failure.

So, to answer from common sense: yes, evolution would select against poor eyesight, but literacy has increased it and technology has nullified selection against it.

[DarrenS]

Hmmm interesting…that brings up another question (yes I’m sort of double-dipping here): How are we affecting evolution? Since nowadays we don’t need to be able to hunt animals for food (just drive to the grocery store), are we selecting for other successful traits? Are we causing evolution to select for people who can pick Internet stocks…or operate computers?

-Darren.

[Chronos]

Another possibility is that it doesn’t matter any more, evolutionarily speaking, because we do have glasses now. Regardless of the true reason, it’s pretty well established that nearsightedness is a lot less common in more “primitive” societies.

[Lance_Turbo]

Will sitting too close to the TV ruin your eyes?

[Smeghead]

*Originally posted by DarrenS *
**Hmmm interesting…that brings up another question (yes I’m sort of double-dipping here): How are we affecting evolution? Since nowadays we don’t need to be able to hunt animals for food (just drive to the grocery store), are we selecting for other successful traits? Are we causing evolution to select for people who can pick Internet stocks…or operate computers?

-Darren. **

I think it’s more along the lines of we’re no longer selecting for anything at all. As technology improves, we’re better and better able to compensate for physical shortcomings. I suspect the incidence of nearsightedness has increased dramatically in the last 100 years or so, though I don’t have any numbers to back me up.

Skills like you mentioned probably have little to do with genetics, so I don’t think we’re selecting for them. On the other hand, I can see how we could be selecting for people who have high metabolisms, so are able to lead a sedentary lifestyle without accumulating a ton of fat and dying.

[bibliophage]

There was a thread on the subject a couple of months ago. http://boards.straightdope.com/sdmb/showthread.php?threadid=26124
Back then I quoted from a web site I found

                          Q: In last week's lecture on myopia, the lecturer said that there is a feedback
                          mechanism to tell the eyeball to stop growing longer so that the person won't be
                          near-sighted but she did not know what the mechanism is. Can it be that if the muscles
                          that adjust the lens are under constant contraction, the brain interprets this constant
                          tension as the eyeball is too short and therefore tells the eye ball to grow longer? So, if
                          one reads too much, the muscles are contracted often which let the brain to tell the
                          eyeball to grow; as a result, the person becomes near-sighted. Does this sound like a
                          reasonable hypothesis?

                          A: I believe this is a proposed mechanism for the development of myopia. Good thinking.
                          Because of this idea, many optometrists suggest to their nearsighted patients to take
                          their glasses off when they read so that they don't need to use those muscles which
                          could stimulate more nearsightedness. In fact, I have heard of some optometrists giving
                          their children bifocals so that their children don't use their focusing muscles in order to
                          reduce the probability of increased nearsightedness.

In the same thread, Arjuna34 noted that “myopia went from 2-9% of
the population at the turn of the century to 35% today.”

[Speaker_for_the_Dead]

Yeah, the basic reason it hasn’t been bred out is that the usual way for a spcies to get rid of defects like that is to have the affected animal die. If they couldn’t pass on genes, then the bad ones would quickly disappear. Because that natural selection is missing in humans…

[popokis5]

Poor eyesight probably didn’t get “bred out”-for lack of better term-because people that are shortsighted can see ok far, vice virsa, etc., and anthropologically speaking our species is a group species that cooperate. So someone who needed glasses to read which was completely unnessary to survive, since most people couldn’t even read until recent times, (and many many still can’t), really doesn’t mean squat evolutionally.