Uyghurs
Contemporary scholars consider modern Uyghurs to be the descendants of a number of people, including the ancient Uyghurs of Mongolia who arrived at the Tarim Basin after the fall of the Uyghur Khaganate, Iranic Saka tribes, and other Indo-European peoples who inhabited the Tarim Basin before the arrival of the Turkic Uyghurs. DNA analyses indicate that the peoples of central Asia such as the Uyghurs are all mixed Caucasian and East Asian. Uyghur activists identify with the Tarim mummies, remains of an ancient people who inhabited the region, but research into the genetics of ancient Tarim mummies and their links with modern Uyghurs remains problematic, both to Chinese government officials concerned with ethnic separatism, and to Uyghur activists concerned that the research could affect their people's claim of being indigenous to the region.
Yenisei Kyrgyz
The Kyrgyz Khagans of the Yenisei Kirghiz Khaganate claimed descent from the Chinese general Li Ling, grandson of the famous Han Dynasty general Li Guang. Li Ling was captured by the Xiongnu and defected in the first century BCE. And since the Tang royal Li family also claimed descent from Li Guang, the Kirghiz Khagan was therefore recognized as a member of the Tang Imperial family. Emperor Zhongzong of Tang had said to them that "Your nation and Ours are of the same ancestral clan (Zong). You are not like other foreigners."
In 758, the Uyghurs killed the Kirghiz Khan, and the Kirghiz came under the rule of the Uyghur Khaganate. However, the Yenisei Kyrghyz spent much of their time in a state of rebellion. In 840 they succeeded in sacking the Uyghur capital, Ordu-Baliq in Mongolia's Orkhon Valley, and driving the Uyghurs out of Mongolia entirely. On February 13 843 at "Kill the Foreigners" Mountain, the Tang Chinese inflicted a devastating defeat upon the Uyghur Qaghan's forces. But rather than replace the Uyghurs as the lords of Mongolia, the Yenisei Kirghiz continued to live in their traditional homeland and exist as they had for centuries. The defeat and collapse of the Uyghur Khaganate triggered a massive migration of Uyghurs from Mongolia into Turfan, Kumul, and Gansu where they founded the Kingdom of Qocho and Gansu Uyghur Kingdom.
When Genghis Khan came to power in the early 13th century, the Yenisei Kirghiz submitted peacefully to him and were absorbed into his Mongol Empire, putting an end to their independent state. During the time of the Mongol Empire, the territory of the Yenisei Kirghiz in northern Mongolia was turned into an agricultural colony called Kem-Kemchik. Kublai Khan, who founded the Yuan Dynasty, also sent Mongolian and Chinese officials (along with colonists) to serve as judges in the Kyrgyz and Tuva regions.