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"If there was a genetic cause for shortsightedness, why is it still around?" - because myopia doesn't significantly affect your chances to produce offsprings.

"If there was a genetic cause for shortsightedness, why is it still around?" - because myopia doesn't significantly affect your chances to produce offsprings. It seems reasonable that being gay does significantly reduce your ability to have children; therefore it is reasonable to expect that if it was an inheritable trait it would have been selected against.

Brian_K_White 6y ago
Everyone keeps saying that, but it's simply not true. We have understood how this is not true for decades or even hundreds of years, and it's not even some impossible concept to grasp. All that's required for a trait to persist, is for it to benefit the pool, not the individual. The only way the seemingly obvious but incorrect idea you descibed applies is, a trait which is good for the group at the expense of the individual, if it's 100% effective like sterility unlike say alarm-calling which merely carries a risk for the individual, is that such a trait can never grow to where all members exhibit it. But it can absolutely be strongly selected for maintaining whatever the optimal percentage is. IE, if it benefits the pool for 10% of members to be sterile, then the percentage of sterile members will not decrease through the mechanism you and so many imagine, but will stay at 10% for as long as the benefit exists.
- dctaflin 6y ago
  And everybody keeps saying THAT. The problem is, that's a secondary effect. A secondary effect is going to have to be pretty strong to counter an obviously anti-competitive primary effect. You can construct scenarios, but I haven't seen any that seem particularly compelling. It seems to me that the default position of "it's not genetic" is much better supported by the data.
- robocat 6y ago
  > All that's required for a trait to persist, is for it to benefit the pool, not the individual. This is a well debunked belief. Genes are selfish, and they only reproduce to the benefit of the gene. Group selection does not occur. An example is evolutionary stable strategies, where cheaters persist in the population, even though the pool would be better off if all individuals in a pool were selfishly altruistic towards pool members.

Brian_K_White 6y ago

Everyone keeps saying that, but it's simply not true. We have understood how this is not true for decades or even hundreds of years, and it's not even some impossible concept to grasp. All that's required for a trait to persist, is for it to benefit the pool, not the individual. The only way the seemingly obvious but incorrect idea you descibed applies is, a trait which is good for the group at the expense of the individual, if it's 100% effective like sterility unlike say alarm-calling which merely carries a risk for the individual, is that such a trait can never grow to where all members exhibit it. But it can absolutely be strongly selected for maintaining whatever the optimal percentage is. IE, if it benefits the pool for 10% of members to be sterile, then the percentage of sterile members will not decrease through the mechanism you and so many imagine, but will stay at 10% for as long as the benefit exists.

dctaflin 6y ago
And everybody keeps saying THAT. The problem is, that's a secondary effect. A secondary effect is going to have to be pretty strong to counter an obviously anti-competitive primary effect. You can construct scenarios, but I haven't seen any that seem particularly compelling. It seems to me that the default position of "it's not genetic" is much better supported by the data.
robocat 6y ago
> All that's required for a trait to persist, is for it to benefit the pool, not the individual. This is a well debunked belief. Genes are selfish, and they only reproduce to the benefit of the gene. Group selection does not occur. An example is evolutionary stable strategies, where cheaters persist in the population, even though the pool would be better off if all individuals in a pool were selfishly altruistic towards pool members.