Where did aikido, calculus, or any other thing that we can claim to know, to label, to learn, or to teach come from in the first place?
Calculus is a very apt example. Who taught calculus to Newton or Leibniz---two people credited with simultaneously and independently (in different countries) inventing what we call calculus? And if that was all there was, how did calculus (and all of mathematics) continue to grow, even today?
Who taught Newton or Leibniz calculus? Who taught O-Sensei aikido?
OK, if that's how you'd like to learn everything. To me it seems kind of akin to throwing out a couple of tens of millenia of human discovery and learning, but to each his own.
Newton's the one who spoke of standing on the shoulders of giants, by the way. He studied what had been discovered by those who came before him, and then extended it further.