What evolutionary advantage could nearsightedness possibly have? I saw a thread

[raccoon]

here not too long ago about possible evolutionary advantages there might be to people being gay. That's what prompted this post.

Like many other people, I've been nearsighted since an early age. Looks like to me like in the hunter-gathering days, people who were nearsighted would be at a distinct disadvantage, and quite likely to not live as long as the average person. So it seems like the gene for nearsightedness wouldn't be NEARLY as common as it must be, to judge by all the nearsighted people there are today.

[trotsky]

1. Here's a neat little writeup covering a possibility.

http://ezraklein.typepad.com/blog/2005/06/the_evolutionar.html

(On edit, I should say that it's not a popular view among evolutionary scientists. Some people believe that myopia is a side effect of the invention of writing.)

[raccoon]

8. Interesting article. Thanks for the link.

Maybe if some of the Neanderthals had been nearsighted, they might still be here. :silly:

[ingac70]

2. No advantage.

I am severely near sighted (helpless without my glasses), and surely would have been eaten by bears or mountain lions if I went hunting/gathering.

[mikelgb]

3. That is where community comes in.

The far-sighted would have been out in the field hunting (feeding , protecting) while the near-sighted who might have been weaving or something like that

[TexasObserver]

4. Your lack of vision would have saved family members from being eaten.

The bad news, of course, is that you would lunch for some other species.

Every animal eaten by a lion serves an evolutionary purpose, just not their own.

[bemildred]

6. Excellent point.

"I don't have to outrun the bear, I just have to outrun you."

[TexasObserver]

33. "Sometimes you eat the bear. Sometimes the bear eats you."

Nature's way.

[bemildred]

5. Lots of advantages:

1.) You make a lousy fighter, so you get to stay home and comfort the women when there is a war going on.
2.) Ditto for hunting big game.
3.) Your close vision makes you a much better gatherer, even as it makes you a poorer hunter.

It is true you don't get no respect.

[mrcheerful]

10. But on a happy note you would be left with the women folk while the he men were away and

just think of all the possibilities that would present to you.

[lumberjack_jeff]

14. With the exception of the last few hundred years...

... nearsightedness wasn't a big liability in a fight. And in fact, hunting was a matter of chasing animals off cliffs.

[bemildred]

15. And you know that how? nt

[lumberjack_jeff]

21. Because a spear is only 6' long. n/t

[bemildred]

24. Go ahead, walk up to that cow and poke it with a spear, see what happens.

Do you know what an "atlatl" is? They are quite old.

[HopeHoops]

7. That's OBVIOUS! I'm nearsighted and can work a mini-screwdriver to put a screw back in my glasses.

You can't DO that if you're far-sighted. Obviously that's the evolutionary advantage.

:evilgrin:

[csziggy]

36. You are so right! I am far sighted and when my glasses break

I have to ask my extremely near sighted hubby to fix them. Without my glasses I can't focus on anything I can reach. Without his, he can't focus on anything past his hand. We make a good match!

[seabeyond]

9. you are the bait for the big bad animal allowing everyone else to get away? nt

[Kurt_and_Hunter]

11. The disadvantages were not sufficient to prevent it

Not everything in evolution is all good. Many traits are part of genetic packages that are adaptive *overall*

If some folks had myopia but were resistant to some disease then there is more myopia passed on, even though it isn't a useful trait.

More importantly, widespread myopia may be a recent phenomenon that could only have arisen (as a survivable trait) in the context of a fairly intricate society.

[hunter]

12. My vision has frozen up at computer monitor distance.

I used to be nearsighted in a minor way, I especially needed to wear glasses when driving at night, but reading and doing fine mechanical or electronic work was easy. Now I have to wear my nearsighted glasses when I drive, and my reading glasses when I do fine work. But I don't need glasses to write at the computer.

Extreme nearsightedness probably isn't good for anyone, in the same way that a double set of sickle cell genes is bad, but as a single set of sickle cell genes protects against malaria, nearsightedness might be of benefit to toolmakers.

On the other hand, there's really no "reason" or "advantage" or "meaning" to anything in nature. Stuff just happens. Every living thing can trace its ancestry back to the beginnings of life but the vast majority of twigs on the tree of life are pruned away. Any signal we extract from the noise is a function of our own mental processes, mental processes that are in themselves an evolved thing. Most of the universe is invisible to us thus the reasons for things we discern are at best very course and at worst artifacts of our own thought processes.

[bemildred]

16. Yeah, that's where mine is too.

But I still read fine without glasses, at 65, and I'll take that.

[TonyMontana]

13. You don't need 20/20 vision to hunt

The only reason we need so called "perfect" vision is to read signs from far away.

[bemildred]

17. But it is an "advantage".

Hard to spot all that game hiding in the brush when everything looks fuzzy.

[JVS]

18. It doesn't have to be an evolutionary advantage

It just has to not be something that would prevent reproduction.

[bemildred]

19. LOL. nt

[Lydia Leftcoast]

20. Even a nearsighted person (I am one) can perceive things like:

"Oh, that big hulk just moved. I guess it's an animal, not a rock. Oh look, it just raised its trunk. It must be a woolly mammoth."

"There's something standing vertically that just moved. It must be a person."

"Og is screaming and running away from one of those moving hulks. It must be a predator."

[Romulox]

22. Nearsightedness is closely correlated with higher IQ.

Recently, I read that some posit that near-sightedness is either caused by, or greatly exacerbated by, lots of reading. So the above may simply be a correlation without any causal relationship. Nevertheless, if nearsightedness is part of the expression of the bundle of genes related to higher IQ, it may be that higher IQ gave us the advantage we needed to survive despite the nearsightedness.

[Skinner]

23. I suspect that the genetic trait of nearsightedness was able to become widespread

only after our ancestors started to take care of one another, and work together in a cooperative way.

If human society really were "every-man-for-himself", then nearsightedness would be a clear disadvantage. But once we learned to work together and help each other, nearsightedness did not harm overall "fitness." So it wasn't weeded out. Those with good eyesight could go hunt, while the nearsighted could contribute in other ways.

[bemildred]

25. A sound argument.

I think you can make good arguments for written language (reading) and the need for fine handicrafts (arrowheads for example, needles, etc.) too.

[Hosnon]

28. I agree with this. It's probably a disadvantageous genetic mutation that was kept at a minimum

until human cooperation and, more recently, the invention of corrective glasses, blunted natural selection's effects.

[WingDinger]

26. There are CLEAR advantages. Your peripheral vision is far better.

You can detect small movements far better. If you still can chuck that spear straight, at distance, you will be a superior hunter. Test this. Blur your vision. You will detect things moving outside your direct gaze with ease. Motorcyclists use this to great advantage.

[Donald Ian Rankin]

27. Myopia mostly affects people over reproduction age, doesn't it?

Once you've sprogged, your genes don't give a shit about you.


The other half of the answer - because certainly some young people are short-sighted too - is presumably that "myopia" doesn't have any advantages, but "not having improved eye design that would reduce the risk of myopia" has the big advantage of your body not needing to devote additional resources to eyes that only a few people would gain from.

[ellenfl]

30. i don't have the stats but i don't think that's the case.

however, in early to mid 40 age range, many people get presbyopia, or far-sightedness, and need reading glasses. as a near-sighted person since the age of 10 (as were both my sisters but not my brother), post-reproductive age clearly had nothing to do with it.

i will ask my sister, who is in the eye biz, if she has any statistical info regarding the prevalence of near-sightedness.

[Manifestor_of_Light]

31. I needed glasses probably before I started school.

Mom said I was reading signs at age three and books at four.
They put me in first grade in private school at age five because they were frantic to get me in school because of my IQ and reading level.

The school nurse would sit with one of those light boxes with Es on it, 15 feet away, and ask me to point which direction the E was. I sat there and quietly said dozens of times, "I can't see that".

Well, she didn't notice. Mom wondered why I always had my nose in a book so she took me to the eye doctor in second grade and found out I needed glasses badly. She said she felt stupid.

Nearsighted people get presbyopia too. The bottom half, the reading half of the lens is weaker, and backed out a couple of diopters (a diopter is a meter, 39.37 inches).

I went into bifocals when I was about 42. I did not know this, because my parents had perfect vision and only wore reading glasses when they were old.

I think there is a correlation with little kids and reading and nearsightedness.

[ellenfl]

32. yup, 42, although i put off getting bifocals for as long as

possible. it was easy with contact lenses because you can wear one reading lens and one distance lens (called, interestingly, 'monovision'). eventually i found that i sometimes had to wear reading glasses. now i just wear my bifocals and take my glasses off to read small print. i know my father was nearsighted very young, probably mom too but in her day 'boys didn't make passes at girls who wore glasses'. i'm sure she took her glasses off when there were cameras around, as did i. vanity thy name is girls wearing glasses.

ellen fl

[csziggy]

37. Presbyopia is the reduced ability to focus up close as you age

Myopia is simple near sightedness, generally from birth.

I have age induced presbyopia. Although my good eye has always been more far sighted than average, up until my mid-forties, I could still focus well enough up close to read without my glasses. (My bad eye is near sighted with very bad astigmatism, close to legally blind.) Now without my glasses I can't focus on anything I can reach. I can still see distances just fine without my glasses, though because of my bad eye, I have to wear glasses to drive.

[DavidDvorkin]

29. While the other guys were out hunting

the nearsighted ones were back in the caves helping out the women. Thus their genes flourished.

[darkstar3]

34. I actually have a thought on this, though it might be overly simplistic.

I recently read that myopia rates have been drastically increasing ever since the ready availability of corrective lenses. If we assume for the moment that this is true, and we take as a given the fact that glasses tend to hide wrinkles and bring out cheekbones, there is a distinct possibility that glasses have been sexually selected for over the last few generations.

"Guys don't make passes at girls who wear glasses" is a load of abject horseshit.

[Manifestor_of_Light]

35. Yep, true. Glasses are part of who I am and always have been.

In my case I don't have a choice; I have to wear glasses or contacts to get any further than the bathroom.

I can be corrected much better in contacts and my eye doc was smart enough to do the monovision thing for the presbyopia (One near lens and one far lens).

An optician explained the numbers on the scrip to me. It's a diopter. A diopter is a meter, or 39.37 inches in English.

Near sighted people have a minus prescription. A minus means the focal length is a reciprocal, or a fraction.

Example: In my good eye, in contacts, I'm a minus four ( -4).
Call a diopter 40 inches. 40 inches divided by 4 is ten inches, so that means my focal distance for that eye is ten inches. My prescription is a higher number in glasses because the lens is not sitting directly on the eyeball.

Farsighted people have a plus number in their scrip.

And a great place to get cheap glasses is www.zennioptical.com

I think people who freak out when they have to get bifocals are terribly vain and don't know how lucky they are. I am just thankful that my eyes are healthy, I have full color and stereo vision and that I can be corrected so I can drive. My mother had macular degeneration in her old age and suffered terribly for it.

[Arugula Latte]

38. I always wondered that too! I was nearly blind sans glasses before I had Lasik.

One reason I got Lasik was I always worried what would happen to me in a fire or earthquake or something if I couldn't find my glasses or they were broken or what have you.

But it seems that nearsightedness should have been weeded out of the gene pool simply because you would have been screwed if you'd been a myopic cave person or even up until relatively recently in human history (and a lot of people in the world don't have access to glasses to this day).

[Fumesucker]

39. I've been fairly nearsighted in one eye and slightly farsighted in the other all my life..

Nearsighted people can do very fine work such as chipping flint to make tools and weapons, the level of craftsmanship in many neolithic tools is remarkable, those who made such things were not amateurs, it took a profound knowledge of the materials and techniques to produce some of the objects we find today.