To add on to the informative sibling comment, historically South China communities have been more isolated from each other due to its rugged terrain, whereas No

To add on to the informative sibling comment, historically South China communities have been more isolated from each other due to its rugged terrain, whereas North China has been dominated by its plains, especially the central plain. Hence the phenomenon that in the North, historically, Mandarin dominated as the lingua franca, whereas the south was host to a staggering variety of Chinese languages.