"Do I know what specific factors make that talent? No. But can I say unequivocally, without a doub that they have 'superhuman' gifts of talent for their respective fields? Hell yes."
Well, I mean, I think there is some equivocation going on, at least. Whenever you call something superhuman you make it a lot harder to figure out what we're really talking about. We don't really have access to what they worked on, how hard they worked -- hell for all we know, Magnus's pre-chess activities could have prepared him for chess. How much of the "talent" is chess specific, how much of it is just determination (because determination can be innate to some extent)... I mean there are plenty of sources of equivocation, here.
It seems pretty unlikely that Magnus is "just like us" or something... on the other hand, that doesn't mean we suddenly know any decent amount about what talent is, it just means, it seems like Magnus has a lot of talent. Well, if we have nothing else, that's something to go by, but it is what it is -- something completely wrong could seem like it was right to us, so one just has to accept the limitations of going by our instincts, and our unbelievable love of attaching the adjective "superhuman" to things that are at a much higher level than us.
Not to mention Stockton and Bird. Both with genetic issues I suppose. What a waste.