Gene study points to link between Stone Age China and the Americas
- New research suggests prehistoric people travelled from China’s northern coastline to North America as recently as 11,000 years ago
- The study suggests they may have travelled along a previously unknown coastal route
According to the study published in international peer-reviewed journal Cell Reports on Tuesday, the Stone Age migrants came out of China in two separate waves, coinciding with some dramatic changes in global climate.
The first event occurred during the Last Glacial Maximum, which was a period of extreme cold, when ice sheets covered much of North America, northern Asia and Europe, around 26,500 to 19,000 years ago.
The second event happened within the last deglaciation, a period of warming and melting ice around 19,000 to 11,500 years ago.
The researchers traced the route of the D4h gene, a specific lineage of mitochondrial DNA that has been found in native populations across North and South America including Chile, Peru, Bolivia, Brazil, Ecuador, Mexico, and California.
Mitochondrial DNA (mtDNA) is passed down from mothers to their children, so it can be used to trace maternal ancestry.
They traced the origin of D4h to ancient and present day populations in China and found that the phylogenetic differentiation of the gene occurred somewhere in central or north China, most likely in a region geographically close to the country’s northern coast.
“In fact, among the north and central China samples [with D4h], more than half were found in provinces along or near the northern coast of China,” wrote the team led by professor Kong Qingpeng from the Kunming Institute of Zoology, part of the Chinese Academy of Sciences.
The possible sites of origin include the modern-day cities of Beijing and Tianjin.
The discovery is important because it sheds light on the ancestry and migration patterns of indigenous peoples. The study supports the theory that early Americans took a coastal route from Asia to America rather than an inland route through an ice-free corridor.
It also suggests that there were multiple waves of migration from Asia to America, which could have contributed to the genetic diversity observed in indigenous populations today.
“In addition to previously described ancestral sources in Siberia, Australo-Melanesia, and Southeast Asia, we show that northern coastal China also contributed to the gene pool of native Americans,” first author Li Yuchun, a molecular anthropologist at the Chinese Academy of Sciences, was quoted as saying in a statement by Cell Press.
It is widely accepted that indigenous Americans are descendants of Siberians who crossed a land bridge in what is now the Bering Strait, but in recent years there has been growing evidence suggesting that other ancestral populations from different regions also contributed to their genetic make-up.
The authors said they surveyed a total of 101,319 Eurasian individuals living today. They also searched for the gene in 15,460 ancient samples that “covered virtually all global reported ancient mtDNA data, as well as additional 232 recently reported ancient mtDNA data from East Asia”.
The large sample size in this study is significant because it allows for a more comprehensive analysis of genetic variation within the D4h lineage and other populations around the world.
By analysing such a large number of individuals, the researchers were able to identify rare genetic lineages that might have been missed in smaller studies.
After comparing the genetic data from contemporary populations to ancient DNA samples, the researchers were able to gain insights into how these populations have changed over time.
Ancient migration events can be studied through the genetic variation present in contemporary and ancient populations, according to the researchers.
Over time, genetic mutations accumulate, and these can be used to track the movement of populations over long periods of time.
The study said the second wave of migration may have happened during the period of deglaciation, when warming weather and melting ice produced favourable conditions for human populations to expand and migrate.
As glaciers melted and sea levels rose, it created a narrow strip of land along the Pacific coast that was free from ice cover. This allowed humans to travel along the coast and eventually reach the Americas, according to the researchers.
“We were surprised to find that this ancestral source also contributed to the Japanese gene pool, especially the indigenous Ainus,” Li said.
Kong said: “This suggests that the Pleistocene connection among the Americas, China and Japan was not confined to culture but also to genetics.”
The idea of a pan-Pacific cultural ring connecting prehistoric settlements in Asia and America is still hotly debated.
Some researchers argue that there is evidence of cultural exchange or diffusion between these regions, while others are more sceptical.
One example of evidence is the use of jade in both regions. Jade was highly valued by many ancient cultures both in East Asia and the Americas.
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Another example is the use of earthen mounds for burial and ceremonial purposes. Earthen mounds were built by many ancient cultures in both East Asia and the Americas, including the Jomon people of Japan and the Hopewell culture of North America.
There are also some similarities in architectural styles between ancient civilisations in East Asia and the Americas. For example, some scholars have noted similarities between the stepped pyramids of Mesoamerica, such as those at Teotihuacan, and certain structures found in China’s Yunnan province.
But the idea of a pan-Pacific culture is controversial – both because there is no direct evidence and because of the practical difficulty of maintaining contact across such a vast distance – and sceptics say these cultural similarities may just be a coincidence.
