There are 56 officially recognized ethnic groups in China. The largest is the Han Chinese, who make up most of the population. Throughout history many groups have assimilated with others or disappeared. The term Zhonghua minzu describes Chinese nationalism in general. Most Chinese speak Mandarin, though there are many languages among the ethnic groups. Chinese characters have had many variants over history and tens of thousands of ancient documents still exist from oracle bones to Qing edicts. Chinese civilization originated in the Yellow River and Yangtze River valleys in prehistoric times. Chinese culture is one of the world's oldest and most complex, with customs varying greatly between different regions.