Scientists used mitochondrial DNA to trace a female lineage from northern coastal China to the Americas. By integrating contemporary and ancient mitochondrial DNA, the team found evidence of at least two migrations: one during the last ice age, and another during the subsequent melt. At about the same time as the Second Migration, another branch of the same lineage migrated to Japan, which may explain the Paleolithic archaeological similarities between the Americas and China and Japan. The study was published May 9 in the journal Cell Reports.
“The Asian ancestry of Native Americans is more complex than previously reported,” says first author Yu-Chun Li, a molecular anthropologist at the Chinese Academy of Sciences. “In addition to previously described ancestral sources in Siberia, Australo-Melanesia, and Southeast Asia, we show that the northern coast of China also contributed to the Native American gene pool.”
Although it was long assumed that Native Americans descended from Siberia who crossed the Bering Strait land bridge, recent genetic, geological, and archaeological evidence indicates that multiple waves of humans may have traveled to the Americas from different parts of Eurasia.
To shed light on the history of Native Americans in Asia, a team of researchers from the Chinese Academy of Sciences has pursued an ancestral lineage path that may link Paleolithic East Asian populations with founding populations in Chile, Peru, Bolivia, Brazil, Ecuador, Mexico and California. The strain in question is in mitochondrial DNA, which can be used to trace kinship through the female line.
Researchers surveyed more than 100,000 contemporary and 15,000 ancient DNA samples from across Eurasia to identify 216 contemporary and 39 ancient individuals belonging to a rare lineage. By comparing the accumulated mutations, geographic locations, and carbon age of each of these individuals, the researchers were able to trace the lineage’s branching path. They identify two migration events from coastal northern China to the Americas, and in both cases, they believe the travelers may have set foot in America across the Pacific coast rather than crossing the ice-free Inland Passage (which would not have been opened at the time).
The first radiative event occurred between 19,500 and 26,000 years ago during the last glacial peak, when ice sheet coverage was at its peak and conditions in northern China were likely unfavorable to humans. The second radiation occurred during the later period of decay, or melting, between 19,000 and 11,500 years ago. There was a rapid increase in population at this time, possibly due to a warming climate, which may have fueled expansion into other geographical areas.
The researchers also uncovered an unexpected genetic link between the Native Americans and the Japanese. During the Decay, another group branched out from the northern coast of China and traveled to Japan. “We were surprised to find that this ancestral source also contributed to the Japanese gene pool, especially the original Ainus,” says Lee.
This discovery helps explain the archaeological similarities between the Paleolithic peoples of China, Japan, and the Americas. Specifically, the three regions share similarities in how they craft projectile points for arrowheads and spears. “This suggests that the Ice Age connection between the Americas, China and Japan was not limited to culture but also genetics,” says senior author Cheng Bingkong, an evolutionary geneticist at the Chinese Academy of Sciences.
Although the study focused on mitochondrial DNA, complementary evidence from DNA from the Y chromosomes indicates that male Native American ancestors also lived in northern China at about the same time as these female ancestors.
This study adds another piece to the puzzle of Native American ancestry, but many other elements remain unclear. “The origins of many founding groups remain elusive or controversial,” Kong says. “Next, we plan to collect and investigate more Eurasian lineages to get a more complete picture of Native American ancestry.”