This is like saying if you fed everyone the EXACT same diet as Yao Ming, the world would be full of 7ft+ people. A central tenant of evolutionary theory is that

This is like saying if you fed everyone the EXACT same diet as Yao Ming, the world would be full of 7ft+ people. A central tenant of evolutionary theory is that there is intra-species variation (serving as the raw material for natural selection to act upon). The brain is also a physical trait subject to variation. Is it so hard to believe that variations in the brain's structure leads to variations in ability?