FUN THEORY TIME!
Now we know the yaungol are descendants of tauren trapped on Pandaria after the Sundering, HOWEVER what if it's infact tauren that descended from yaungol? My clue... Niuzao the Black Ox! Now Niuzao is a August Celestial, which I personally believe are Ancients. As we know many beastial creatures such as furbolgs. quilboar & murlocs came from Ancients so why not tauren/yaungol? We already know tauren predate the Titans arrival so could it be that yaungol came from Niuzao and in turn tauren are a variation of yaungol that quickly changed to adapt to Kalimdor whilst the yaungol remained the same on Pandaria