I was listening today to NPR’s Science Friday, and on off-topic remark came up that made me think (hey, it happens). The Important Scientist said that he was badly nearsighted, and before glasses, he wouldn’t have lived to adulthood because he would have been effectively blind (more prone to accidents, etc.). Since he would have died early, presumeably he wouldn’t have the opportunity to reproduce, thus eliminating his bad eyesight gene from the human pool.
I buy the above hypothesis. With that, why has our eyesight gotten so much worse in the last few hundred years? I asked around today and no one could think of a reason that made much sense to me. The major ideas tossed around were:
War. Only people with perfect vision went to war. They died. I think this is bull because the % of war deaths compared to the population as a whole is miniscule.
Change of environment. In “Ye Good Old Days”, things that our eyes focused on were generally further away. Today, we read/focus on more things that are closer, which strains our eyes. I think this is bull, because humans have always had to focus on close items, back to the foraging for food days.
AFAIK, no one knows why, but the proportion of nearsighted people has risen dramatically in the last 100 years. There’s still controversy over the cause of myopia, so it’s no surprise that no one can explain why it’s on the rise, either.
Last year in university our biology teacher talked about this during a discussion on evolution. As was mentioned in a couple of the posts in the “glasses” link, one factor she touched on was Darwinism. It seems that glasses started becoming more widely available to the general public around the same time that eyesight started getting worse… coincidence? As we started to find technologies to take care of individuals with less-than-perfect physical traits (and genes), they started living longer more productive lives and probly had more kids, so begining the downwards spiral. This combined with more reading (manditory education), usually by dim candel light, may have also contributed. While I’m not totally convinced that good eyesight has been a prerequisite to making babies right up until glasses were invented, you can’t deny the theory outright. How many people have bad knees, backs, low stamina, and are rather weak compared to the average Amish farmer or Hutterite… or even their own grandparents (when they were young)? Don’t completely overlook the old “use it or loose it” theory; it works on genetics fairly quickly.
ps - another thought; perhaps part of the significantly higher percentage of bad eyesight is due to a much higher percentage of people going to see a proper optomitrist and the prevelance of bad eyesight therefore being more accuratly reported. I don’t think very many dusk-till-dawn home steaders back in the 1800’s managed to haul themselves and their six kids into town every year for a full medical; my grandparents sure didn’t! “It looks a little fuzzy? then squint and get back to work!!!” You can see other examples too - 150 years ago causes of death were generally attributed to having a “bad heart”, or “blood poisoning”, or died of “old age”, etc… With today’s medical technology those three diagnosis could mean hundreds of different things from high cholesteral, hardened arteries, bacterial infections, cancer, and so on. Now that we know what and how to look for it, we “see” a lot more.
I’m surprised a university professor would have such a misunderstanding of evolution. Removing evolutionary pressure would not cause reversal of evolution, only the slowdown of it.
Obviously if the defect (poor eyesight) can be treated in a way that allows the genes to stay in the pool, by artificial means (glasses), then Mother Nature no longer regards the condition as a weakness. So the trait flourishes better than it would before glasses.
Mother Nature IS a bitch, but she is easily fooled.
You guys are missing the obvious correlation. There are more documented cases of near/farsightedness because there are more optometrists to diagnose them.
Since glasses have only been available to the majority of Westerners since round about WWII, this major change in human physiology has happened in aound two generations. That’s what I call evolution!
Only people with good eyesight went to war??? My take is through the years anyone they could get their hands on went to war. This leads to poor sighted people to die more often.
Also I’ve been thinking of all the ailments we’re correcting (like vision) and think this is not good long term as the poor genitcs will be passed on more often.
You wouldn’t need a large group to impact the gene pool. But I agree there must be other greater causes. One might be the fact that for thousands of years, humans have been free of the usual survival of the fittest rules that the rest of the animal kingdom still faces. We don’t have to notice a predator to make it through the day.
A blind wildebeests is toast, humans have taken better care of the afflicted, at least as far back as biblical times.
Perhaps more people are being tested. When my parents were in grade school, there was no universal testing (or at least they didn’t mention it). There was when I was in school (in the 60’s). So, who’s to say that all those little kids back in the 30’s didn’t need glasses? Certainly is true for back in the 1800’s and so on.
Frankly, as one who was seriously myopic prior to diagnosis (my first set of glasses were a higher prescription than my mom’s who’d had glasses for many years), until you’re shown how other folks see, you don’t really know that you can’t see.
Plus - standard of living changes. Glasses, eye doctors etc. can be expensive, so as our standard of living has risen, there may be more $$ available.
People are living longer and as they age they develop presbyopia (inability of the lens to focus on close objects). So, some one with 20/20 vision, when he or she gets to be 40 or so, will not be able to see close objects clearly, the ability to do so degenerating with age.
Now, if that person was slightly myopic - say 20/50 or so - when he or she got older, he or she would be able to see close objects clearly. It’s a compromise. Far objects would be slightly blurred, but they’d continue to see close objects well all their lives.
That is my take on it. However, it doesn’t account for all of us who are severely myopic.
Supposedly this has been taken into account in the studies (although I don’t have any cites at the moment).
As I posted in the previous thread, one theory is the use of nightlights in the rooms of small childern, as described in this CNN article about a study published in Nature. This would be a good explanation, but this later CNN article cites a later Nature article that invalidates the earlier study.
Hey! Call it anechdotal, but my eyesight is rapidly getting worse. I squinted my way thru highschool, got glasses to correct my nearsightedness for the next 35 years, got bi-focals at 40 to help my close-up vision, and now I need tri-focals!
To answer the OP yes, eyesight is rapidly getting worse!
About the biology teacher having a “misunderstanding” of evolution(from The Ryan’s post); she didn’t. Removing an evolutionary pressure can indeed cause a reversal of evolution, in fact it usually DOES happen that way (careful about using the word “reversal” -more like that trait no longer being selected for). Remember evolution ain’t a one-way street… if a population of organisms starts to get bigger it’s not written in stone that they will continue to grow at varying rates until the end of time. If good eyesight for example is an advantage or neccesary, the population over time would devellop it (more like those with bad eyesight would be killed off or out-competed). If at some point it no longer gives an edge over others, it gradually becomes less common or less highly develloped while some other trait does. Why are massive jaws, keen physical senses, and big rugged muscular frames becoming uncommon now? -we don’t need them anymore… but check out our brains compared to those of 10,000 years ago!
-going a bit off-topic, but I just can’t let some comments slide that easily.
Your distance vision is not getting worse. If anything, it will get better as you age due to dehydration of the cornea, causing the focal point to extend out further, more towards the retina. What you are experiencing is the normal process of presbyopia. Your lens cannot accommodate as they could when you were younger, requiring bifocals. The 3d lens is to cover the space between what your bifocals can see and your regular distance glasses can see. But the prescription of your far vision should be no worse, and may even be better (less diopters). IANAD
