By extracting DNA information from the bones and teeth of 166 ancients, the formation history of East Asian populations is finely analyzed by genome sequencing.
Author 丨Gan Xiao
"Black eyes, black hair, yellow skin, forever and ever a descendant of the dragon." We Chinese often pride ourselves on our "descendants of the dragon" bloodline.
Tracing back to our roots, as East Asians, who were our ancestors and how did we get here? What is the relationship between the various ethnic groups?
On February 22, the academic journal Nature published a research paper on the collaboration between Professor Wang Chuanchao's research group at the Institute of Anthropology of Xiamen University and the team of Harvard Medical School Professor David Reich. The study, together with 85 co-authors from 43 units around the world, used genome sequencing to finely analyze the formation history of East Asian populations by extracting DNA information from the bones and teeth of 166 ancients.
Screenshot of the dissertation web page
"Snowball" "Questioning"
"Who am I?" Where am I from? Plato's ultimate philosophical proposition still puzzles mankind to this day. In recent years, anthropologists have tried to answer this question from an evolutionary perspective with the help of advanced life science technologies.
Around 2015, Wang Chuanchao, who was full of strong curiosity about the life of East Asians, led the team to launch this scientific research project. "In the beginning, our plan was to find samples of ancient people's bones, teeth and other samples from archaeological sites across the country, extract DNA, sequence them, and reveal their genetic relationships." Wang Chuanchao introduced to China Science Daily.
The research team has obtained a large number of ancient samples from archaeological sites in Shaanxi, China and Taiwan, China. However, the ancient stories told by these samples did not give the researchers a satisfactory answer.
As a result, they looked at the wider geographical space, expanding from China to the surrounding Russian Far East, Japan and other places, and the number of research teams joining the research was also increasing. "For example, if you want to know how a certain group of people came to be 5,000 years ago, you may have to chase it 6,000 years or more, and you also need information about the people around them." Wang Chuanchao said.
An analysis of samples from the Russian Far East found that the samples were more closely related to ancient humans near Lake Baikal, which inspired them to ask further questions.
"Geographically, the Russian Far East is almost the end of human migration, and further north and east is the Indyne Strait and the Pacific Ocean, which are not suitable for survival." Wang Chuanchao and researchers analyze. They speculated that these ancient humans probably came from the Mongolian plateau west of Lake Baikal, and that this group of people most likely crossed the entire Mongolian plateau and connected to the Eurasian steppe.
In 2019, Wang Chuanchao invited researchers from Mongolia to join the team and obtained samples from local archaeological sites to test this hypothesis.
In this 6-year-long study, it was the continuous pursuit of scientific questions, and the scientific research team continued to expand like a "snowball", and finally, 85 co-authors from 43 units around the world completed the work.
The largest "East Asian" archaeology
The study has obtained important conclusions such as "Sino-Tibetan homology" and "South Island and Zhuang Dong homology". "The RESULTS of DNA studies show that the ancestors of the Yellow River Basin had a homologous relationship with the populations of the Central Plains and the Qinghai-Tibet Plateau about 5,000 years ago, which indicates that they are the ancestors of both the Han people in the Central Plains and the ancestors of the Tibetan-Burman population." Wang Chuanchao explained. This conclusion also validates the linguistic theory of "Sino-Tibetan homology".
At the same time, the study also provides direct evidence for the hypothesis that the Austronesian language population originated in the southern region of Chinese mainland, that is, "the South Island and Zhuang Dong are cognate". Researchers believe that the ancestors who originated in the southern region of Chinese mainland are likely to reach Taiwan through the southeast coast, and then migrate and expand to Southeast Asia and far Oceania.
In addition, questioning of Lake Baikal and the Mongolian plateau refutes the linguistic hypothesis that the expansion of the agrarian population of the Xiliao River contributed to the spread of proto-Transeurasian. This is due to the fact that experiments on the DNA of the ancients have found that more than 8,000 years ago, the hunter-gatherer populations on the vast lands of the Mongolian plateau, Lake Baikal and the Heilongjiang River basin were indeed the ancestors of the Mongolian and Tungusic peoples, but were not genetically significantly affected by agricultural populations more than 2,000 years ago.
It is understood that this is the largest archaeological genomics research in East Asia currently carried out in China. "The amount of genome samples of ancient people in East Asia reported in this study is twice that of the total samples published by domestic research institutions in the past, and we hope to change the long-term lag in archaeological genomics research in East Asia, especially in China." Wang Chuanchao said.
The second generation of sequencing is a contribution
In the opinion of the researchers, the success of this research is directly due to the rapid development of second-generation sequencing technology.
Wang Chuanchao deeply felt that around 2000, genetic sequencing cost about $1 per site, and the cost of measuring a human genome was as high as $20 or $3 billion, and now it only costs 3,000 yuan.
The high-throughput sequencing technology developed around 2010 has greatly improved efficiency and reduced costs, opening the door to a new world for paleoanthrophnology research.
"As you can imagine, ancient humans were buried in the soil after their deaths, and their DNA was constantly degrading and corroding, and there were many microorganisms and pathogens in the soil." Wang Chuanchao pointed out, "When we dig them out today, we actually have to restore this person's DNA information from a pile of degraded and contaminated bones, and the new sequencing technology helps us get useful information from a large amount of data." ”
In addition, the ultra-clean laboratory is also the "standard" for paleoanthrophnology research, and the Institute of Anthropology of Xiamen University established this "sharp weapon" in 2017. Researchers need to wear protective clothing, goggles, masks, gloves, hoods, and go through the wind shower chamber to enter this "space-time tunnel" and meet ancient humans.
Wang Chuanchao et al. working in the ancient DNA ultra-clean laboratory (photo courtesy of the research team)
For this research result, Yang Yimin, a professor at the School of Humanities of the University of Chinese Academy of Sciences, commented: "This is only the beginning of the story, with the publication of more ancient genome results, I believe that the face of human migration on the chinese land in the past 10,000 years will become clearer and clearer." ”
Thesis link: https://www.nature.com/articles/s41586-021-03336-2