An ancient clan, sure, but the ancestors of all Shinobi?
So you're saying that everyone is either Senju or Uchiha?
If Rikudou was an Uzumaki, that would mean that Uzumakis are the ancestors of all shinobi.
Then that would mean everyone is descended from the Uchiha or the Senju, correct?
Borrowing the reasoning behind your argument.
Which is why the phrase is meant metaphorically. The Sage was the one who established the paradigm of Ninjutsu. He was not the first to use or discover chakra (the Samurai are evidence of this), he was 'merely' the first to begin teaching people how to form chakra within their bodies for use in various "release" techniques.
Though I suspect it will be shown that the Hyuuga predate the Sage, and that they are the original "sages." The Hyuuga, after all, embody Taoist principles; and work on the principle of manipulating their opponent's chakra. It would make sense that particularly enlightened or sensitive Hyuugas would lean toward the manipulation of nature chakra around them.
It was, however, the Sage of Six Paths who first practiced the art of absorbing nature chakra and combining it with his own for the purpose of ninjutsu.
The Uzumaki, as compared to the Hyuuga, were likely comparable to shaman and more 'ritualistic' evocations of chakra (sealing jutsu, the shrines and ritualistic artifacts).
The two concepts combined to create what is now known as ninjutsu. Senjutsu was a more advanced understanding inspired by the Taoist principles of the Hyuuga.
Or perhaps I'm simply too enamored with Hinata for my own good.
