Since numerous naturally preserved mummies from the Bronze Age were discovered in the Tarim Basin in western China at the beginning of the 20th century, their origin has been controversial. Genetic analyzes have now cleared up the riddle: According to them, it was apparently a local, genetically isolated indigenous population that had not mixed with neighboring peoples.
Culturally, on the other hand, the people probably maintained an exchange with their neighbors. This is indicated by studies of the tartar of the mummies, which suggest a diverse diet with foods from different parts of China.
At the beginning of the 20th century, researchers found astonishing mummies in the Tarim Basin in the western Chinese province of Xinjiang: The Bronze Age bodies were not only naturally preserved by the dry desert climate, but also displayed extraordinary characteristics. Many looked more like Europeans in appearance, and their woolen clothing, as well as archaeological evidence of agricultural practices, indicated that they were both ranching and farming. The origins of these people puzzled researchers for a long time. It was speculated that they could have descended from the Afanasievo, wandering steppe herders from what is now southern Siberia, or from farmers from the Central Asian mountains or the desert oases in northern Afghanistan.
Genetically isolated population
A team led by Fan Zhang from Jilin University in China has now solved the ancestry puzzle. To do this, the researchers analyzed the DNA of 13 mummies from various sites in the Tarim Basin, which were dated to around 2100 to 1700 BC, and of five mummies from the northern Dzungarian Basin, which were dated to around 3000 to 2800 BC. The mummies examined are considered to be the oldest human remains found in Xinjiang so far. The researchers compared the DNA with genome data from numerous other ethnic groups living then and now. In addition, they analyzed the tartar of seven individuals from the Tarim basin and were able to draw conclusions about the diet of the people.
The result: “Our analyzes show that the individuals from the early Bronze Age in Dzungaria predominantly have an Afanasievo ancestry with an additional local contribution,” report the researchers. “The individuals from the Early and Middle Bronze Age in Tarim, on the other hand, only have a local ancestry.” Even individuals from widely separated sites in the Tarim Basin showed a close genetic match. “Although they are geographically separated by more than 600 kilometers of desert, they form a homogeneous population that has apparently gone through a considerable genetic bottleneck,” the researchers say. This finding refutes the previous theories about the origin of the mummies from the Tarim basin.
Cosmopolitan Relations
The analysis of the tartar resulted in another surprise: “Despite their genetic isolation, the Bronze Age peoples of the Tarim Basin were culturally remarkably cosmopolitan – they ate wheat and dairy products from West Asia, millet from East Asia and medicinal plants such as seaweed from Central Asia,” says co-author Christina Warinner from the Max Planck Institute for the History of Man in Jena. “The harsh environment of the Tarim Basin may have been a major obstacle to the flow of genes into the region, but not to the flow of ideas or technologies.”
The combination of nutritional and genome data also showed that the people from the Tarim Basin also ate dairy products in adulthood. But unlike previously thought, they were lactose intolerant. “The Tarim mummies are thus contributing to a growing body of evidence that prehistoric dairy farming has spread in Inner and East Asia regardless of the genotypes of lactase persistence,” the researchers conclude.
Deeper understanding of human migration history
“The reconstruction of the origin of the mummies from the Tarim Basin has fundamentally changed what we know about this region. We will now investigate further ancient human genomes from other epochs in order to gain an even deeper understanding of the human migration history in the Eurasian steppes, ”says Zhang’s colleague Yinquiu Cui.
In an accompanying commentary on the study, which was also published in the journal Nature, the anthropologist Paula Doumani Dupuy from Nazarbayev University in Kazakhstan writes: “Zhang et al. address longstanding disagreements about the origins of the mummies from the Xiaohe culture. Scientists must now work together to further explain the dynamic and diverse patterns of cultural exchange that made up the Bronze Age of Inner Asia. “
Source: Fan Zhang (Jilin University, Changchun, China) et al., Nature, doi: 10.1038 / s41586-021-04052-7