Believe it or not, the number of practicing mathematicians and PhD students who have the innate grasp that a Terry Tao does are few and far between. The vast majority have to work hard to earn their skill.
No amount of hard work would have allowed Stephen Hawking to succeed at sports.
Some pursuits are simply unavailable to those without the requisite immutable attributes. This is not politically comfortable, but it is true. I think the only legitimate question is whether mathematics is such a pursuit, and I'd like to be proved wrong on that point, but trying to convince me that anyone can do anything they put their mind to is wasted effort as it is so plainly contradicted by the available evidence.
What about those people in this world with genetic abnormalities that affect brain function? Would you expect someone with Prader-Willi syndrome to be able to become competent at mathematics if they only worked hard enough at it? At what point does “hard enough” become “virtually impossible” or even “definitely impossible”?
Why, sure - from the physics standpoint all the human brains are essentially the same, they all consist of the same protons, neutrons, electrons... (Also, they are close enough to being spherical.)
You're begging the question. Please substantiate.