Ancient DNA reveals Silk Road's melting pot: Western ancestry found in Gansu tombs

In a pioneering study, scientists from Fudan University in Shanghai have delved into the ancient DNA of individuals from a mass cemetery in Gansu province, revealing compelling insights into the genetic makeup of Hexi Corridor residents dating back over twelve centuries.

This research, the first of its kind, utilizes ancient DNA data to explore human migration along the Hexi Corridor, a pivotal hub on the historic Silk Road.

Published in mid-December in the Science Bulletin, the study unveils two major immigration waves spanning the past two millennia.

The Hexi Corridor, primarily located in present-day Gansu province, serves as a narrow yet crucial link connecting the heartland of ancient China, the Central Plains, to the Western Territory, encompassing areas such as the current Xinjiang Uygur autonomous region and parts of Central Asia. Defined by lofty mountains and arid deserts, this ancient pathway comprises dotted cities founded along short rivers fed by melted snow.

Historical documents attest to the Hexi Corridor's historical significance, acting as a crossroads where Western and Eastern civilizations converged through trade, religion, and occasional conflicts following the establishment of the Silk Road during the Han Dynasty (206 BC-AD 220).

As technological advancements in molecular biology open new avenues for exploration, archaeologists are increasingly drawn to analyzing DNA samples from ancient tombs to validate historical accounts or uncover previously undocumented narratives.

Led by Wen Shaoqing from Fudan University's Institute of Archaeological Science, the team successfully extracted DNA data from teeth and temporal bones at the Heishuiguo site near Gansu's Zhangye city and the Foyemiaowan site near Dunhuang in the western part of the Hexi Corridor.

The DNA analysis, encompassing 25 individuals from the Han to Tang Dynasty (618-907), pinpointed two outliers from the Foyemiaowan site, dating to the Wei Dynasty (221-265) and the Tang Dynasty. Further scrutiny revealed approximately 30 percent and 50 percent western Eurasian ancestry, respectively, suggesting these individuals were likely descendants of unions between western Eurasian females and local males.

Despite being interred in a mass cemetery, these individuals received equal treatment from their families, indicating the openness and tolerance of ancient Dunhuang, as highlighted by a researcher quoted by Xinhua News Agency. This discovery aligns with existing materials found in the Mogao Caves in Dunhuang, reflecting the diverse cultural elements prevalent during that era.

The team's comparative analysis of data samples and present-day genetics of Hexi Corridor residents led to the conclusion that contemporary Han Chinese in Gansu and specific ethnic groups within the corridor, such as Dongxiang, Bonan, and Yugur, carry more western Eurasian lineages than their ancient counterparts.

The study identifies a significant genetic amalgamation approximately 600 to 1,000 years ago, a period coinciding with the expansion of the Mongol Empire in the early 13th century. Historical records suggest that Genghis Khan and his sons recruited soldiers and artisans from Central and Western Asia during this time, with some settling in the Hexi Corridor. The Yuan Dynasty, established by Genghis Khan's grandson Kublai Khan, further contributed to migration, defending the Hexi Corridor.

The team postulates that this genetic mix is partially attributed to these migrations. In contrast to foreign elements introduced centuries ago, the western Eurasian elements from this period displayed no discernible gender inclination, indicating migration to the Hexi Corridor likely occurred in family units.

Experts highlight this as the second major migration period, marked by a significant shift in the gene pool. The first, occurring from the late Neolithic period to the Han Dynasty, witnessed large-scale migration organized by Han rulers in response to the establishment of the Silk Road.

Historical records validate the migration facilitated by Zhang Qian's visit to the Western Territory, resulting in the creation of the Silk Road. Han rulers migrated hundreds of thousands of people and soldiers from the mid-lower reaches of the Yellow River to cultivate plants, establish counties, and defend the link. DNA data corroborates these historical records, affirming major genetic changes resembling people in the lower reaches of the Yellow River.

The communications in ancient times between the East and the West have always been a hot topic among researchers, Wen said, adding that the team will continue to explore the process in a longer period or larger areas.