Do you mean Americans, or just people who aren't black? There are probably more Brazilians in the upper tier of the sport than any other race. The Japanese are doing well in the lighter weight divisions as well. Pride has always been good about bringing in fighters from all over the world, they have a Japanese lightweight champ (Gomi), an American WW champ (Dan Henderson), a Brazilian MW champ (Wanderlei Silva), and a Russian HW champ (Fedor). Now that's diversity if you ask me. The UFC as a brand on the other hand, has always just been big in the States, so naturally they tried to promote mostly American fighters, (LW champ Sherk,WW champ Hughes, former Mw champ Franklin, LHW champ Liddell, and HW champ Sylvia) Lately though, since MMA's burst in popularity, the UFC has been bringing in more foreign fighters to break that mold (Anderson Silva,Cheick Kongo,Yushin Okami,Yuki Sasaki, Alessio Sakara, Hironaka, Ansar Chalangov just to name a few) I think it only appears whites dominate in the UFC, but in most other major organizations that isn't the case.