Not everybody hunted. Most of the women didn’t, for example. If they could see well enough to gather plants and care for children, they could still be productive members of the tribe even if they were nearsighted.
Once there’s a bit more specialization, there are lots of jobs a nearsighted person could do. They could make arrowheads or pottery, for example.
There’s evidence that early human groups cared for people who were disabled. Humans are social animals.
High insulin levels apparently affect the incidence of near-sightedness, and modern diets high in refined carbohydrates tend push up insulin levels. (ISTR reading somewhere that one of the hormones controlling eyeball growth is chemically related to insulin, but don’t have a cite.)
Here’s an article about it, and here’s an abstract of a paper relating myopia to diabetes, with links to papers on PubMed.
Nope, the dirty foreigners introduced optical glass to the chinese. China had almost no glass manufacturing before contact with Europeans.
I’ve been an Optometrist for about 20 years. It appears that development of myopia requires BOTH genetic inheritance AND immersion in a visually “stressful” near-work environment (school). Without both, you will not become nearsighted. The gene would not have been eliminated in the past, because it was not a problem (expressed) until “modern times”. It is no coincidence that the “geeky” child and adult are usually depicted with thick glasses. They do the most near work. The “jock” is rarely depiced as such, for obvious reasons.
Also, one could think of myopia as an adaptative advantage to those few individuals who could read in ancient times. They could do their near work all day long, well into old age, and not need any type of visual aid. Hence, the gene has a potential positive role. This still holds true for many of my patients.
Of course, I could be wrong.
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Yeah, but it helps if you also live long enough to raise your children.
I don’t know about problems starting in adulthood. My nearsightedness started when I was 8 or 9, and got steadily worse through my teenage years, but it has leveled off a lot now. Then you have a whole different set of problems that come in middle or old age.
I’ve had glasses since age 7*, so there goes the “good sight until age of reproduction” theory. Beyond about 25 feet, I wouldn’t recognize a blob of colors as potentially human unless it were about the right size and moving. The only logical explanation is that I come from a long, unbroken line of tribal shamans, because no way in hell am I descended from a long, unbroken line of great hunter/gatherers.
Makes me feel better, anyway.
*I Pit my glasses-wearing Mom. 80-year-old Dad still doesn’t need glasses most of the time. :mad:
I didn’t get glasses until I was 15, up to a year after I could no longer read the chalkboard from even the front row, because despite my myopia, I had a reputation for being sharp-eyed. I’d learned to focus on other details (e.g., on many occasions, I identified friends by the way their indistinct dots bobbed from their personal gait, while my better-sighted friends couldn’t identify them at that range from their accustomed cues like clothing, facial features etc., or might not even notice that there was someone there.
Good sight and sharp eyes may not be the same thing. I was a good tracker, instinctive marksman, etc. despite my vision, so it took everyone, myself included, far too long to realize that I needed glasses. Then for 30 years, prescription drifted over a small range (typically swapping strong-eye and weak-eye every visit) until my last check happened to land me on exactly my original teen prescription.
I take this as a sign that presbyopia is imminent.
Not living long enough to raise your children doesn’t matter so much if you live in a group with other adults in which another group member will take in orphans. That’s how pretty much all humans have always lived. We’re not solitary like, say, polar bears, where if the mother dies before her cubs are old enough to fend for themselves, the cubs will die (I think there are examples of mother polar bears adopting cubs, but it’s the exception rather than the rule).
Damn straight, me too. I had Eyes of The Mole a long time before puberty arrived.
Interesting that a lifelong love of books and computers may have helped me reach my current exalted status of -12.25/-13.00.
:eek: because it looks vaguely speccy.