So, the theory is that the Trolls were the origin of all these guys. Not Darkspear, the other ones, Zanzibar or whatever. At some point they all broke off and somehow ended up where they are now. Seems to make sense when you look at them, though.
Hmm, we got trolls, elfs, gnomes, goblins, tauren, draenei, and humans down… what next? >)