NEW YORK – A southern Chinese province that borders Vietnam appears to have been home to several historical populations and the site of gene flow between those populations over thousands of years, according to an ancient DNA sequencing study focused on the region.
"Our results show heavy interactions among three distinct ancestries at the crossroads of East and Southeast Asia," co-senior and co-corresponding author Qiaomei Fu, a researcher affiliated with the Chinese Academy of Sciences and Shanghai Qi Zhi Institute, and her colleagues wrote in a paper published in Cell on Thursday.
For their study, the investigators started with 170 samples from Guangxi, a southern Chinese province that is bordered by Vietnam to its west, ultimately using ancient DNA capture and sequencing methods to assess some 1.2 million SNPs in 30 Guangxi samples ranging from a few hundred to nearly 11,000 years old. To that set, they added available sequence data for an individual known as Qihe3 from China's Fujian province — a coastal region that falls east of present-day Guangxi and Guangdong provinces.
By comparing the 31 ancient genomes to one another and to ancient individuals sequenced in the broader region in the past, the team uncovered three main ancestral groups in southern China and Southeast Asia: a group with deeply diverged East Asian ancestry near what is now Guangxi (represented by a 10,400- to 10,700-year-old individual dubbed Longlin from Guangxi's Laomaocao Cave), a group of Hòabìnhian hunter-gatherers from Southeast Asia, and a group related to the Qihe3 individual with Early Neolithic Fujian ancestry.
While these groups were genetically separated more than 10,000 years ago, the researchers' findings also pointed to population interactions in the area between around 6,000 and 9,000 years ago, when individuals from the Guangxi and Fujian groups and the Guangxi and Hòabìnhian groups met and mingled, leading to Guangxi populations that had local East Asian ancestry, Fujian-related ancestry, and hunter-gatherer ancestry.
"Unlike in the Fujian region, the existence of highly admixed populations in Guangxi suggests that this region was an interaction zone among Indigenous populations from Guangxi, populations from the Fujian region, and populations related to Hòabìnhians of Southeast Asia," the authors wrote, noting that the results are consistent with gene flow prior to farming that "played an important role in forming the pre-agricultural populations in these regions."
More recently — between roughly 500 years ago to some 1,500 years ago — the Guangxi individuals appear to have shared closer genetic ties to individuals from Tai-Kadai and Hmong-Mien language groups remaining in the region into the present.
"The historical Guangxi populations in our current data show that ancestry related to Tai-Kadai speakers can be found by at least [about 1,500] years ago, while ancestry related to Hmong-Mien speakers is found in individuals dating to [about 500] years ago," the authors reported, noting that "these two populations have lived continuously in Guangxi for at least 500 years."