, suggesting that modern life somehow causes nearsightedness. But how? Nobody knows.

There is a very plausable theory based on natural selection and genetics that does explain this phenoma.
It is believed the gene/genes responsible for myopia are dominant genes, but for the first 200,000 odd years people with the gene/genes responsible for myopia did not see the lion comming untill it was too late and therefore did not get the opportunity to procurate and pass the gene on so by the time the 17 Century came around, a very very triny % of the population had myopia and we learnt to correct for it with specticales. Since it’s a dominant gene,. tyhat small % grew exponnentialy. This also explains the low levels in populations of people arriving late to modernity.

The gene being dominant would have no impact whatsoever on how quickly the gene would spread.

I must be nearsighted. I don’t see a link. :smiley:

You dont think a dominant gene that has been suprerssed by selective pressure would spread quickly if the selective pressure was removed?

The information is cleverly hidden in the “Will sitting too close to the TV ruin your eyes?” article …

The numbers The Master gives is first generation 0% (read as <0.5%), second generation 8% and third generation 59%, and that “The shift among the Eskimoes was too sudden to be explained by genetics alone”.

With only 1 in 200 people having the dominate gene, I don’t see it dominating the gene pool after just two generations … unless it’s associated with incredible horniness, but that’s counter-indicated by the 1 in 200 number we started with.

I agree that it would spread quickly, if “quickly” means 10 or 20 generations … that’s not a God-awful long time.

Except that, even without the selective pressure against it, there’s still no selective pressure for it. Which means that it’s only going to spread via genetic drift, and absent a cataclysmic population bottleneck, that’s incredibly slow.

I suspect that the OP misunderstands just what it means for a gene to be dominant. It does not mean that if you have the gene, then all of your children will have it, too (that’s a surprisingly common misconception, even among those who should know better). All it means is that if you have both that gene and the recessive one, the trait you show will be the dominant trait, but your children can still inherit either one from you.

Of course, before the days of tiny print, there might not been too much of a selection pressure against myopia. It’s like dyslexia. We did great for tens of thousands of years until some goofball invented writing. Now, we’re special.

Okay, we might not have done great before writing (I should sneak around the left side of that wooly mammoth and stab it while you go on the right? Okay, sounds like a plan. Now which side is my left again?)