In their chronology, the Yangshao is indeed the original culture, but they attribute the Xia to the Longshan. Interestingly, no mention is made of different ethnicity's, and no evidence is offered to prove that the Xia enslaved the Mongols.
When visiting the Chinese governments Website, one would note that the Chinese still imply that they descent from Peking Man (Homo-Erectus), of course this is racist nonsense. A genetic study done by researchers from all over the world: China, Japan, U.S.A. U.K. and other countries, and published in 2001; definitively answered the question of Chinese origins.
The findings were that the original Chinese were 100% pure Black African, with absolutely no outside admixture - But here again, we are talking about the original Black Chinese, modern Chinese are quite different.
The Yangshao culture is followed by the Lungshan, after which comes the Yin, or Shang, which dates to about 1,500 B.C, and is by far the better known. For many years, the Xia Dynasty was thought to be a mythical time that the Chinese tell about as part of their oral history.
Though the Xia Dynasty existed in oral histories, there was no archaeological evidence found of it until 1959. Then excavations at Erlitou, in the city of Yanshi, uncovered what was most likely a capital of the Xia Dynasty.
This site showed that these people, were direct ancestors of the Lungshan/Longshan culture. Radiocarbon dates from this site, indicate that it existed from 2100 to 1800 B.C. Despite this new archaeological evidence of the Xia, they are still not universally accepted as a true dynasty. Shang Chariot and horse burials
Chariot horse burials are found from Greece to China, but they are relatively rare except in China and the bones are often very poorly preserved. The earliest chariots and chariot burials in China date to the Shang dynasty, at around 1250 BC (Linduff 2003). Their use in the Shang period mainly seems restricted to royalty. But during the succeeding periods the burial of chariots and horses became much more widespread.
Most Shang chariots were driven by two horses. Chariots pulled by four horses did not become widespread until the Spring and Autumn period. In some situations horses were buried in pits with chariots either side by side or one in front of the other. Some pits contained only horses and others only chariots. Sometimes the horses were buried in the main tomb while the chariots where in separate pits, while at times the reverse was the case (Lu 1993).
A Shang period (11th century BC) horse and chariot pit M52 from Guojiazhuang, (Anyang, (Henan). The men and horses had been killed and lain in the pit before the chariot was lowered into it (Zhongguo Shehui Kexueyuan Kaogu Yanjiusuo Anyangdui (CASS 1988; Bagley 1999). A Western Zhou period horse pit, Tianma-Qucun (Houma, Shanxi).
The horses were apparently buried alive, with their feet tied together. Unfortunately there are no lifelike statues of the Xia in China, just these jade and bronze works, (that have been made available anyway). However, there are lots of them in the Americas.
A 2008 study by Jilin University showed that the Yuansha population has relatively close relationships with the modern populations of South Central Asia and Indus Valley, as well as with the ancient population of Chawuhu. In 2007 the Chinese government allowed a National Geographic Society team headed by Spencer Wells to examine the mummies' DNA. Wells was able to extract undegraded DNA from the internal tissues. The scientists extracted enough material to suggest the Tarim Basin was continually inhabited from 2000 BCE to 300 BCE and preliminary results indicate the people, rather than having a single origin, originated from Europe, Mesopotamia, Indus Valley and other regions yet to be determined. 
In years 2009-2015, the remains of in total 92 individuals found at the Xiaohe Tomb complex were analyzed for Y-DNA and mtDNA markers.
Genetic analyses of the mummies showed that the Xiaohe people were an admixture from populations originating from both the West and the East.
The maternal lineages of the Xiaohe people originated from both East Asia and West Eurasia, whereas the paternal lineages all originated from West Eurasia.
Mitochondrial DNA analysis showed that maternal lineages carried by the people at Xiaohe included mtDNA haplogroups H, K, U5, U7, U2e, T and R*, which are now most common in West Eurasia.
Also found were haplogroups common in modern populations from East Asia: B5, D and G2a.
Haplogroups now common in Central Asian or Siberian populations included: C4 and C5.
Haplogroups later regarded as typically South Asian includedM5 and M*.
The paternal lines of male remains surveyed nearly all – 11 out of 12, or around 92% – belonged to Y-DNA haplogroup R1a1, which are now most common in West Eurasia; the other belonged to the exceptionally rare paragroup K* (M9).
The geographic location of this admixing is unknown, although south Siberia is likely.