Ancient DNA study reveals population history of western Tibetan Plateau

According to a study published in Current biology May 22, the genetic components of the ancient populations of the western Tibetan Plateau are closest to the ancient populations of the southern Tibetan Plateau, and their main genetic components have been maintained over the past 3,500 years. Furthermore, these ancient populations on the western Tibetan Plateau had complex and frequent interactions with ancient populations inside and outside the plateau.

The study was carried out by the team of Professor Fu Qiaomei from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and archaeologists from the Tibet Institute of Conservation and Research cultural relics and other institutions.

Ngari Prefecture, located in the western part of the Tibetan Plateau, is the crossroads connecting the Tibetan Plateau, South Asia and Central Asia, and a potential migration route for early human populations. Previous research has confirmed that genetic components linked to Central Asian populations affected this region around 2,300 years ago, but the genetic history of earlier populations in this region was unclear.

In this study, researchers sequenced genome-wide nuclear data from a total of 65 individuals from six sites dating back 3,500 to 300 years ago in Ngari Prefecture. The newly sequenced data covers six archaeological sites, including Gebusailu, Laga, Sangdalongguo, Pulanduowa, Qulongsazha and Guge Ganshi Cave.

By combining the newly sequenced data with previously published ancient genomic data, the evolutionary history of populations on the western Tibetan Plateau over the past 3,500 years has now been reconstructed.

This study is a systematic, long-term genomic study of ancient populations from the western Tibetan Plateau. According to the researchers, this is of great importance for the in-depth understanding of the history of interactions between ancient populations of the Western Plateau and ancient populations of the neighboring Plateau and South and Central Asia.

Genetic characteristics of ancient Western Plateau populations and their interactions with ancient Plateau populations

Previously, understanding of the genetic history of ancient Western Shelf populations was extremely limited. Based on a single site dating back 2,300 years ago, the researchers hypothesized that genetic influence had occurred between populations from the Western Plateaus and populations from Central Asia. However, the precise time, place and extent of this influence were unknown.

In this study, researchers reconstructed the evolutionary history of the Western Plateau population over thousands of years using genetic information from various ancient Tibetan populations.

They showed that ancient Ngari populations from 3,500 years ago had similar genetic components to southern shelf populations and did not carry additional genetic components from Central Asia or South Asia.

This genetic composition has been stably maintained in northwestern Ngari Prefecture for over a thousand years: the genetic composition of the late Gebusailu and Laga populations from 2,300 years ago is almost the same as that of the Gebusailu population 3,500 years ago.

In other words, the Ngari population during this period mainly carried the genetic components of the ancient southern plateau populations, while the Central Asian and South Asian genetic components were introduced much later.

Subsequently, by 2,300 years ago, Central Asian components appeared at some sites in northwest Ngari Prefecture, but until 150 years ago the proportion of Central Asian components was still less than 15%. Overall, local Ngari genetic components remained dominant from 3,500 to 150 years ago.

Researchers also discovered complex interactions and migrations between populations on the plateau. By 3,500 years ago, the genetic components of ancient populations on the southern and western parts of the plateau were very similar, indicating that migration and population expansion from south to west may have occurred earlier.

In addition, compared with the population in northwest Ngari, populations 1,800 to 1,600 years ago from the Kongque River to the upper reaches of the Xiangquan River, southeast of Ngari, have been more influenced by the ancient populations of the southern plateau. This indicates that the peoples of the southern plateau may have begun to expand westward again before the Tubo Empire expanded westward in the early 7th century.

In summary, interactions between ancient populations of the southern and western plateaus were far more complex than those recorded in historical records. As early as 1,800 years ago, multiple east-west human migrations between the two locations had occurred, and a gradient of genetic components introduced by the expansions can be observed in these east-west populations.

Interactions between ancient populations of the western plateau and off-plateau

Although Central Asian components began to affect some Ngari populations around 2,300 years ago, the proportion of Central Asian components in the genomes of these populations is low (<5%).

On the one hand, these results provide genetic evidence for cultural interactions between ancient populations of the plateau and ancient populations of neighboring Xinjiang, Central Asia, and South Asia. On the other hand, they also reflect the fact that such cultural interactions between plateaus were accompanied by limited migrations or mixing of populations.

For 2,000 years, genetic components linked to South Asia have also affected the Ngari Prefecture region. Interestingly, the South Asian-related genetic components that affected ancient Ngari populations came from mixed populations that settled in Central Asia. These populations are genetically related to Central Asians but are culturally typical of South Asians. Previous research suggested that they were immigrants from the Indus Valley Civilization who settled in Central Asia.

This is the first identification of genetic components linked to South Asia in ancient Tibetan Plateau populations, providing clues to interactions between ancient Plateau populations and those linked to the Tibetan Valley civilization. ‘Indus.

In the 9th century AD, with the decline of the Tubo regime, the descendants of the Tubo royal family founded the Guge kingdom in present-day Ngari Prefecture. It was not until the 17th century AD that the Guge kingdom collapsed. As a continuation of the Tubo lineage, the Guge population provides an important window into the genetic characteristics of the later Tubo people.

An ancient human sample collected by Guge Cave researchers showed the influence of Central Asian populations, and the proportion of Central Asian components reached 31%. This mixing event is estimated to have occurred around 1353 AD, coinciding with the prosperity of the Guge Kingdom.

This new result shows that in addition to its historical ties to the South Asian kingdoms, the Guge Kingdom also had demographic interactions with people from the Central Asian kingdoms.

Kinship practices in the first communities of the Western Plateau

Researchers also examined the relatedness among individuals from early sites on the Western Plateau. In the Gebusailu tomb dating back 2,300 years ago, a second generation family structure consisting of a father and two sons was discovered.

At the same time, individuals at this site and the 1,800-year-old Pulanduowa site were predominantly male, and the diversity of Y chromosome haplotypes is obviously lower than that of mitochondrial haplotypes, indicating that both could have been communities dominated by paternal inheritance. .

The 1,600-year-old Qulongsazha Tomb includes a family lineage in which second and third generation descendants are related by maternal kinship, suggesting the role of maternal kinship in the family lineage. Combined with sex ratio and paternal and maternal genetic diversity, this model reflects a relatively balanced paternal and maternal inheritance structure.

Nevertheless, this study constitutes a preliminary exploration of kinship practices at early highland sites, and future research with more samples will shed more light on the details and diversity of the community structure of ancient Tibetans.

Due to the high altitude and harsh natural environment of the western Tibetan Plateau, anthropological and archaeological research in this region is relatively limited. In particular, large gaps exist in previous research on the evolutionary history of early ancient populations of the western Tibetan Plateau and their interaction with ancient populations in neighboring regions.

By combining genetics and archaeology, researchers have studied in depth the evolutionary history of ancient populations on the Western Plateau over the past 3,500 years. Although the major genetic components of ancient Western Shelf populations show continuity, these populations had complex and frequent interactions with ancient populations of the adjacent Southern Shelf region, Central Asia, and offshore South Asia. of the board.

As the Tibetan Plateau is a bridge between East Asia, Central Asia and South Asia, the results of this study are important for understanding the genetics of ancient populations of the plateau and the interactions of these populations with the ancient Central and South Asians.