NEW YORK – Using whole-genome sequencing data, a team from China, Hong Kong, and the US has started to untangle genetic relationships and migration histories for the diverse populations found in a mountainous region in southwestern China bordering the eastern Tibetan Plateau.
"The Tibetan-Yi Corridor (TYC) region between Tibet and the rest of East Asia has served as a crossroad for human migrations for thousands of years," co-senior and co-corresponding author Shengbin Li, a biosciences researcher at Xi'an Jiaotong University, and his coauthors wrote, noting that "previous claims regarding the history and structure of TYC populations inferred by linguistics are incompatible with the genetic evidence."
The researchers performed genome sequencing on blood samples from more than 240 individuals in the Tibetan-Yi corridor, representing more than a dozen ethnic groups in the region, and six Han Chinese, Hui, or Mongol individuals from northern China. The findings, which appeared in Cell Reports on Tuesday, suggested that populations in the region share broad genetic ancestry, with more nuanced population patterns influenced by historical migrations and geographic barriers.
"The [Tibetan-Yi corridor] region is a meeting point between many East Asian populations, especially those closely related to the Han, Tibetan, and southern East Asians. Our genetic results highlight the complexity of their population history, with a similar complex admixture," the authors wrote, adding that "some clear patterns can be observed."
The investigators found that genetic relationships in the region did not strictly follow linguistics-based population lines but reflected complex population genetic patterns influenced by the region's geography. Likewise, they noted that population relationships appear to be more nuanced and complex than would be predicted from straightforward north-to-south migrations during the Neolithic, as predicted from past research.
When the researchers analyzed the new genome sequences alongside more than 2,500 genomes from the 1000 Genomes Project, almost 300 Simons Genome Diversity Project genomes, and genome sequences previously generated for 68 Tibetan Highlander individuals, they saw genetic ties between populations in the northern part of the Tibetan-Yi corridor and individuals in highland Tibet.
Populations in the southern part of the Tibetan-Yi corridor appeared to be more genetically similar to individuals in Southeast Asia, particularly Thai and Cambodian populations, the team noted, while a population known as Achang showed signs of genetic drift reflecting a relatively long history of isolation.
"The TYC region is the key to understanding the fundamental migration patterns and divergence between humans in East Asia and Southeast Asia," the authors wrote, noting that their genetic analysis "portrays a gradual change in genetic relationships from north to south."
In a statement, senior author Li noted that "[m]ore studies are needed to further understand the origin and flow of the region's population, especially a more comprehensive analysis that incorporates not only genetic but also archaeological, cultural, linguistic, and geographical evidence."