Mitochondrial DNA Analysis Of Three Ancient Populations In Northwest China

Northwest region of China is a vast geographic area connecting East and West, an area extending from Shanxi, Ningxia, Qinghai and Gansu, far into the region of Xinjiang. Population migrations took place continually in this region throughout its history, and the inhabitants of this region were composed of admixed populations of various physical types, cultures, and languages.The Lajia site is located in the Guanting basin of the upper Yellow River, in Minhe county, Qinghai province, northwestern China. According to radiocarbon dating, the Lajia site is 3800-4000 years old. Archaeological studies have associated the Lajia site with the late period of the Qijia culture, a major culture that flourished during the late Neolithic Age to early Bronze Age in the Hexi Corridor, a major route leading to the central regions of the Yellow River. The Qijia culture belonged to the cultures of the Di-Qiang, an ancient tribe confederation in northwestern China. According to ethnological studies, the Di-Qiang population contributed to the development of the current Han and Tibeto-Burman (TB) speaking populations. In 2000, archaeologists working in the northeast part of the Lajia site discovered 16 human remains in two ruined houses, designated F3 and F4. Excavations at the site revealed that the cause of the death of the inhabitants was a sudden earthquake followed by a flood. The Lajia civilization ceased to exist after this natural disaster, so that the Lajia site is sometimes termed"the eastern Pompeii"by archaeologists. In the present study, we used mtDNA analysis to investigate the maternal relationships of the ancient inhabitants and their relationship to modern populations. The results provide valuable new insights into the familial relationships of the Lajia specimens as well as their relationship to modern Han and TB populations. MtDNA analysis reveals that the 14 subjects found in the Lajia site shared some close maternal kinships. However, the detection of different haplotypes in individuals within the same house excludes the possibility of a matrilineal social structure. All of the ancient sequences were identified as Asian haplogroups based on the sequence of the mtDNA HVI region and corresponding RFLP sites within mtDNA coding region. The mtDNA haplogroups B, C, D, M* and M10, that were detected in the ancient individuals demonstrate the specificity and continuity of part of the mitochondrial gene pool over several millennia in this location. The geographic distributions of these detected haplogroups in the modern Han and TB populations indicate that the ancient people that lived in Northwest China may contribute to the maternal gene pool of these modern populations, which is consistent with their ethnic history.The Yuansha site is located in the center of the Taklimakan Desert, in the downstream of the Keriyan River, Xinjiang Province, northwestern China. Archaeological studies show that the period of the Yuansha site is not later than the Western Han Dynasty. The Yuansha site is the oldest that has been discovered in the Taklimakan Desert to the present. Recently, the origin of the Tarim Basin population has come to be of great interest. At present, the archaeological evidence that supports the indigenous origin hypothesis is insufficient. It is widely acknowledged that three cultures from different regions contributed to the origin and development of the Tarim Basin civilization. One is nomadic culture from the Russo-Kazakh steppe, north of the Tarim Basin. The second influence is Eastern culture. The third influence oases culture is from west of the Tarim Basin and north Central Asia in the Bronze Age. The aim of this study is to investigate the genetic relationships between the Yuansha population and the present and ancient Eurasian populations, and to explore the origin and migration history of populations in the Tarim Basin as well as Central Asia. phylogenetic analysis reveals the branch of the Yuansha population is closest to the branch of the ancient Chawuhu population, and has a relatively short distance from the Tajikistan population (SHU) branch. Moreover, these three branches cluster with the branch of the Indus Valley populations. The Yuansha population branch, located between the branches of Europe and India, is closer to the latter. Compared with the North and East Asian branches, the Yuansha branch appears more closely aligned to the South Asian branch, occupying the position between the branches of South Asia and Europe. This indicates that the genetic contributions from Southwestern Asia to the ancient Yuansha population are relatively significant, as compared to East or North Asia. The MDS analysis shows how the populations can be grouped together according to their geographic distributions. Among ancient populations, the Yuansha has a closer affinity with the Chawuhu and Turfan popul- ations, while the genetic distance between the Yuansha and Yanghai is relatively grear. Compared with these modern populations, the Yuansha has a closer relationship with Tajikistan (SHU) and Uzbekistan (UZB), as well as with the populations in the Indus Valley, including the Baluchistan (BAL) and Karachi (PAT) populations. The ancient Yuansha population mainly reflects an early eastward population migration in Eurasia.Hami site is located in the east of Xinjiang, dationg back to Bronze and Iron age. Archaeological studies show that the archaeological culture of Hami site possessing both the east and the west components. The mtDNA lineage of Hami population is composed of Western and Eastern matrilines. Tajimas'D test and mismatch distribution analysis show that Hami population has experienced population expasion in recent time. The demographic analysis of haplogroups suggest that the populations of Northwest China, Sebiria and Central Asia have contributed to the mtDNA gene pool of Hami population. Principal component analysis show that compared to the other Central Asian popultions, Hami population was affected by the East Asian and North Asian populations distinctively. The genetic distance between Hami and Teleut populations was reletively close. Multiscall analysis reveals reletive close relationship of Hami and Zhagunluke populations. Of East Asian popultions, Lajia population had close affinity with Hami population, which provides the molecular data for their cultures affiliation.Above all, this study reveals the genetic structure of early popultions in Northwest China, and their relationships with other Eurasian populations. MtDNA study of the three Northwest populations of China provides valuble informatrion of the early population migration and admixture of this region.