Last week, Prime Minister Hu Jintao rushed home from the G-8 summit to deal with massive unrest and deadly violence in what's called the Shin-jung Uighur Autonomous Region in China's far west. For the first time, the government announced that paramilitary police opened fire, killing two Uighurs and injuring a third. That violence has been followed up by a security crackdown, a scenario much like that in Tibet before the Olympics. Muslim Uighurs once were the majority in a province the size of Texas. Now they're being squeezed by a government-sponsored migration of Han Chinese. But Tibetans and Uighurs are by no means alone among 56 ethnic groups whose cultural and linguistic differences are exaggerated by economic inequality. As the government prepares to celebrate what it calls 60 years of “harmony,” we hear about potential threats to central authority.