Joel of Far Outliers has a post called “Traditional China: Multilingual” on the Hawai‘i Reader in Traditional Chinese Culture, a book that tries to “capture the complexity of the Chinese cultural mosaic” and “take into account virtually every aspect of traditional culture, including sources from the non-Sinitic ethnic minorities,” in which he quotes the introduction on the many languages spoken in China:
Take language, for example. When one thinks of what defines “China,” perhaps the first thing that comes to mind is that it is a place where the people all speak “Chinese.” But what is this “Chinese” that everyone is supposedly speaking to each other? Unfortunately, China does not today possess, nor has it ever in the past possessed, such a universally understood tongue. For starters, we have to take into account the tens of millions of speakers of non-Sinitic languages who make up a significant proportion of the population of the Chinese nation as it is currently configured…. These languages belong to such disparate groups and families as Tibeto-Burman, Austroasiatic, Austronesian, Turkic, Tungusic, Iranian, and Slavic. These are the “minorities” of the Peoples Republic of China, all of whom have roots that lie deep in the past of East Asia, West Asia, Central Asia, Southeast Asia, and Northeast Asia.
It goes on to discuss the complex linguistic facts subsumed under the rubric “the Chinese language,” succinctly and well. The post and the linked introduction deserve reading, and the book sounds like an excellent place to start learning about the diverse place that is China.
Incidentally, anyone who wants a more detailed look at the linguistic situation should get hold of S. Robert Ramsey’s The Languages of China (reviewed here).