History of Mongolia
Although the Xiongnu finally had been split into two parts in AD 48, the Xianbei (or Hsien-pei in Wade–Giles) had moved (apparently from the east) into the region vacated by the Xiongnu. The Xianbei were the northern branch of the Donghu (or Tung Hu, the Eastern Hu), a proto-Mongol group mentioned in Chinese histories as existing as early as the 4th century BC. The language of the Donghu is believed to be proto-Mongolic to modern scholars. The Donghu were among the first peoples conquered by the Xiongnu. Once the Xiongnu state weakened, however, the Donghu rebelled. By the 1st century AD, two major subdivisions of the Donghu had developed: the proto-Mongolic Xianbei in the north and the Wuhuan in the south.
Xiongnu
In the 1920s, Pyotr Kozlov's excavations of the royal tombs at the Noin-Ula burial site in northern Mongolia that date to around the first century CE provided a glimpse into the lost world of the Xiongnu. Other archaeological sites have been unearthed in Inner Mongolia and elsewhere; they represent the Neolithic and historical periods of the Xiongnu's history. Those included the Ordos culture, many of them had been identified as the Xiongnu cultures. The region was occupied predominantly by peoples showing Mongoloid features, known from their skeletal remains and artifacts. Portraits found in the Noin-Ula excavations demonstrate other cultural evidences and influences, showing that Chinese and Xiongnu art have influenced each other mutually. Some of these embroidered portraits in the Noin-Ula kurgans also depict the Xiongnu with long braided hair with wide ribbons, which is seen to be identical with the Ashina clan hair-style. Well-preserved bodies in Xiongnu and pre-Xiongnu tombs in the Mongolian Republic and southern Siberia show both Mongoloid and Caucasian features. Analysis of skeletal remains from sites attributed to the Xiongnu provides an identification of dolichocephalic Mongoloid, ethnically distinct from neighboring populations in present-day Mongolia. Russian and Chinese anthropological and craniofacial studies show that the Xiongnu were physically very heterogenous, with six different population clusters showing different degrees of Mongoloid and Caucasoid physical traits. These clusters point to significant cross-regional migrations (both east to west and west to east) that likely started in the Neolithic period and continued to the medieval Mongolian period.