Mitochondrial DNA Analysis Of Ancient Population From The Taojiazhai M5 Site

Qinghai province, located in northwest of China and adjoined with xinjiang, Tibet, Sichuan and Gansu province, is an important part of the Silk Road. According to the archaeological studies, Qinghai province is considered to be the home of Di-Qiang people, and then reined by Han people at Han dynasty. The Taojiazhai site is in Xining city, Qinghai province, east to Beichuan River and west to Daye Mountain. Archaeological studies have shown us that the Taojiazhai cemetery is dated from Donghan to Weijin (about 2000 years ago), and the people in M5 were probably from the same family. There were 15 human remains in M5 site, and 14 of them were skulls. Because the period from Donghan to Weijin is important for the assimilation between the Han people and Di-Qiang people, the Taojiazhai people provide a perfect sample to study this processes.The application of the techniques of ancient DNA (aDNA) allows us to build and recuperate the hereditary constitution of ancient people, and provide the clues about people's origin, migration, and evolution. In this study, we tried to discuss the relationship among M5 site, and the relationship between M5 people and modern people.We used 3 pairs of primers to amplify a 360bp segment on the mtDNA hypervariable region I, and obtained all 14 sequences. Compared to the Cambridge standard sequence (CRS), 20 polymorphism sites were detected. The consequence that 14 sequences belongs to 8 haplotypes, and 3 of them were shared by more than one individuals (haplotype 2: XN2 XN4 XN10 XN12;haplotype 3: XN3 XN6 XN9;haplotype 7: XN7 XN8), reflected three main maternal lines. Qinghai province has been patriarchy since the late phase of Donghan, and the predominant mode of inheritance is patrilineal heredity. So there were always many maternal lines in one family. The results mentioned above suggest us that the Taojiazhai people may be from the same family.The 14 sequences were assigned to 6 haplogroups by analyzing the high variable region I sequencing, the APLP on coding region and the high variable region II sequencing. 4 sequences were assigned to F, 4 sequences were assigned to A, 2 sequences were assigned to Z, 2 sequences were assigned to B, 1 sequence was assigned to D and 1 sequence was assigned to M. The F haplogroup presents with a relatively high frequency in southern China. The frequency of the F haplogroup in the Han population of Guangdong province is 25.3%. The A haplogroup presents with a relatively high frequency in northern China, especially in the Han and Tibetan population of Qinghai province, but low frequency in southern China. Haplogroup B predominates in Southeast Asia and declines northward. The frequency of the B haplogroup in the Han population of Guangdong province is 26.3%, and also distributes in the Han and Tibetan population of Qinghai province. The Z haplogroup is frequent in northern China, but rare in southern China. D4 predominates for the northern Han but has a relatively low frequency in the south China. In Qinghai province, D4 is the most frequent haplogroup in the Han population (18.2%). In a word, the frequent haplotypes A, D and Z in northern China and the prevalent haplotypes F and B in southern China are all involved in Taojiazhai people.By comparing the same haplotypes in GENEBANK, we find that the people who sharing the same haplotypes with Taojiazhai people are mainly distributing in East Asia, especially in Han people of China. We selected 5 modern people: Han people in Qinghai, Tibet people in Qinghai, Han people in Liaoning, Han people in Guangdong, Qiang people in Sichuan as comparing people to discuss the relationship between Taojiazhai people and modern people. The result reveals the Taojiazhai people have the closest relationship with Qiang people, followed by Han people in Liaoning. This result accords with the history of Qinghai province.Then we compared the result with Lajia site, which is dated back 3,800–4,000 years, and about 100 kilometers away from Taojiazhai site. Results from analyses of APLP typing and HVI motifs suggested that the Lajia people belonged to the haplogroups B, C, D, M*, and M10. The D haplogroups in Lajia people and Taojiazhai people shared the same haplotype. The B haplogroups in both sites shared the same motif 16140 and 16189. The high mutation frequency at 16223 in Lajia people is also common in Taojiazhai people. This result showed that the ancient Taojiazhai M5 people have the genetic continuity with Lajia people who lived 2000 earlier.Because of the special period of these samples, the migration of the Han people will inevitably influenced the life of local residents. We wish our studies could contribute to the further investigation of assimilation of nationalities, the origin of the Han people and the formation of southern and northern Han people.