The Han Chinese are a mix of many groups over time, and here are some of the likely groups:
- A proto-Chinese group in southern China, which likely also became the Vietnamese in current Vietnam;
- A group of Tibetan-related peoples from current Sichuan and Tibet (the Qin dynasty had its roots among a horse-breeding people in Sichuan and Shaanxi).
- Other peoples we know little about from Sichuan, and which we know something about from the Sanxingdui excavations;
- Other non-nomadic groups.
This is just from the pre-Qin unification in the second century BCE.
The period following the collapse of the Han dynasty and running through to the Sui dynasty was also a time of extreme chaos and “mixing of peoples”; one interesting dynasty during this period was the Northern Wei – Wikipedia, which was also called the Tuoba Wei. From a historical point of view, the Tuoba Wei started as a Turkic group which voluntarily adopted Han Chinese culture, and intermarried with Han Chinese, and then disappeared. Some surnames which Chinese still carry today are originally Turkic names which can be traced back to the Northern Wei dynasty. This was the first case of a non-Han Chinese people who decided to voluntarily give up their original identity in peacetime and without coercion.
We know that the Tang dynasty was very cosmopolitan; for example, we know that the Tang forces which fought the Muslim forces at the Battle of Talas – Wikipedia were led by Gao Xianzhi, who was a Korean. We also know that many Turks served in the Chinese military Turks in the Tang military – Wikipedia.
The Tang dynasty represented the last attempt by the Han Chinese to extend their influence into central Asia until the Qing dynasty, and was brought to a spectacular halt by the An Lushan Rebellion – Wikipedia. Up until this rebellion, there was a strong mid-eastern influence in the Tang court, and Chang-An, the Chinese capitol, had a population of one million, with ambassadors and emissaries from the mideast and east Asia.
An Lushan was himself a Turk. The internal fighting from this rebellion cost 35 million lives over an eight-year period, and it is safe to assume that more Turkic, Manchu and Korean peoples mingled and intermarried with Han Chinese in northern China, and adopted Han Chinese language and culture.
This led to the Tang-Song transition where the Chinese population center shifted from northern China to southern China. Prior to this, southern China had been relatively undeveloped; now the development was mostly in southern China. It also explains why the Cantonese from Guangdong province usually refer to themselves as “Tang people” 唐人 and why Chinatown’s around the world are called 唐人街。
All this explains why the Han Chinese are not so much a single people, but a group of peoples who have been bound together over time by sharing a common language and culture, and intermarriage, which form the Han Chinese identity.