| I'd love to see the article as well. Having said that, from a genetic standpoint it's possible to have it so that just certain stable percentage of population has a given trait. How can it be selected for - be eliminating whole villages/societies that have a wrong ratio. Imagine you need 5% of population to be crazy risk takers with no survival instinct. Any more and a village collapses, but any less and you won't have anyone take certian risks when necessary. Now, let's assume that the gene is encoded in mitochondrial dna (carried from mother to child, no influence from father). Also, nobody can really tell who has the gene uless a disaster strikes and such a gene is very helpful for survival or reproduction. So if a generation T has X% of this gene, T+1 will most likely have X% too. Originally, nobody has the gene. So all the societies kind of manage to go by without it. Then one woman has it by random mutation. Her is now 1%, others are 0%. But then a disaster strikes. And villages with 0% die off. 1% villages die off too, but not as much. After the disaster they are now the majority. In one of the villages, a woman with the gene, by pure chance) had more children than usual. In that village the ratio is 5% now. Disaster strikes again, and only villages with 5% are left. Villages where the ratio increases above 5% through chance again, die because the chaos ensues. Villages with lover ratios are decimated once in a while. One day people invent ways to protect themselves from the disaster, and ways to cope with above 5% ratio too. Then the gene will begin slowly drifting in one direction or another. But it will take generations for proportions to change significantly, and it's not certain if the geme will disappear or dominate the population ultimately. I'm not syaing that this is the case with sleep, but that's the wyanit might work. |