Comment by dgfl

It could also be that their brain is somehow just more optimized. Some extreme outliers (e.g. Von Neumann or Tao) don’t seem to have any significant gaps in their abilities. Although Von Neumann did die of a brain-related issue, so perhaps what was gained in efficiency was lost in reliability. Kind of like tuning an engine.

But this is biology after all. Most likely, plain improvements with zero downsides, very narrow improvements at the expense of something else, and improvements at the expense of life expectancy, are all possible mutations.