structural:scholar_edition, structural:reformatting
Demographics

It was during the Northern and Southern dynasties period that the earliest recorded mass migration of ethnic Han to southern China (south of the Yangtze River) took place. This sinicisation helped to develop the region from its previous state of being inhabited by isolated communities separated by vast uncolonized wilderness and other non-Han ethnic groups. During this period, the south went from being nearly a frontier to being on a path to the thriving, urbanized, sinicized region that it became in later centuries. In his book Buddhism in Chinese History, Arthur F. Wright points out this fact by stating:

"When we speak of the area of the Yangtze valley and below in the period of disunion, we must banish from our minds the picture of the densely populated, intensively cultivated South China of recent centuries. When the aristocrats of the remnants of the Chin ruling house fled to the Nanking area early in the 4th century, the south contained perhaps a tenth of the population of China. There were centers of Chinese culture and administration, but around most of these lay vast uncolonized areas into which Chinese settlers were slow to move".

During the Northern and Southern dynasties, the Yangtze valley transformed from a backwater frontier region with less than 25% of China's population to a major cultural center of China with 40% of China's population, and after China was subsequently unified under the Tang dynasty, they became the core area of Chinese culture.