I think at the upper levels of intelligence, you are talking about the engineering limits of the brain as a physical thinking machine. Everything is working as

I think at the upper levels of intelligence, you are talking about the engineering limits of the brain as a physical thinking machine. Everything is working as well as it can; in this case, I suspect the difference between the top 100th percentile and the top 10th is not all that great. That's not to say there isn't a competitive advantage, just that it levels off, like it does in athletics.