Q. Why do so many people have lousy vision? Why hasnt evolution given us better eyesight?
A. Seems to us this whole evolution business has been pretty much a waste of time weve been mutating for millions of years, and we still need glasses.
The way evolution is supposed to work is like this: Two hunter-gatherers go looking for some wild game. One guy has keen vision, and hes able to discern which critter is the slowest afoot. He dashes out of the bushes and gathers the animal in his customary fashion (if were not mistaken, the usual technique in prehistoric times was a swift, disabling bite to the throat).
But the other hunter-gatherer has lousy eyesight, and all he sees is a bunch of fuzzy shapes, and so he starves, and his genes arent passed on, and good eyesight is thus selected.
So why do so many people need corrective eye wear?
Three reasons:
1. Modern society is a strain. The hunter-gatherers didnt have to stare at computer terminals all day or scrutinize the agate listings in the sports section. Children who read books suffer worse vision problems than those who dont. But as optometrist Michael D. Jones of Athens, Tenn., points out, I would much rather my child be nearsighted and be a good reader.
2. It doesnt really matter. Poor vision from birth, or blindness, certainly doesnt preclude survival, because other senses become keener. And there is also a pecu- liar correlation between myopia and certain kinds of intelligence, which is why smart, nerdy kids often have thick glasses.
3. Presbyopia. At about the age of 40, almost every human being starts to have trouble with near vision. This is because the unusual tissue that makes up the lens of your eye has never been sloughed off or replaced, like most tissue. Its been there since you were an embryo. The tissue gradually becomes less elastic, and by the age of 40, its hardened up and doesnt focus as well.
Natural selection didnt affect presbyopia because during most of the time humans have been evolving, hardly anyone lived to the age of 40 anyway. As we always say, anyone over 40 is really just a technological marvel, i.e., a freak of nature.
