China's minorities number over 80 million people. Some of these ethnic groups, the Zhuang, Miao, Yi, and others, have been under Chinese political power and cultural pressure for nearly two thousand years. The Muslims and the Kaifeng Jews survived in China, whereas the 18th-century Christians were suppressed, because they followed through with their accommodation policy. There was no unique authoritative external power, like the Pope in Rome, to exacerbate the political conflicts. The problems of integration and assimilation are, of course, at least as much of a political as of a religious or ethnic nature. Chinese governments have always been conscious of a possible breakaway due to language, race, national origin or religion. The earliest concrete evidence for the existence of Judaism in China comes from the Tang dynasty, although Jewish traders may well have visited China earlier.