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New Ancient DNA Discoveries Show Native Americans Returned to Siberia
A discovery of gene flow and migration paints a realistic but complicated prehistory of northern Asia and the peopling of the Americas following the last Ice Age
Three people perished on a riverbank in northeastern Siberia's Kamchatka Peninsula some 500 years ago. Their remains have revealed an intriguing fact, they have some North American ancestry based on their DNA. This finding was published in Current Biology1 two days ago. The findings indicate that although the progenitors of today's Native Americans originated in Asia, the migration was not one-way when taken into account alongside other ancient and modern genomes. Instead, the Bering Sea region served as a crossroads where people frequently traveled by boat across continents for thousands of years.
This is not entirely new. According to a study2 from 2019, genetic and linguistic data demonstrated that humans who lived in northwest Alaska between 2,200 and 500 years ago may have somehow crossed across the Bering Sea into Siberia. It was not known, however, whether this gene flow of Native American heritage back into Asia was typical or an anomaly. As a result, the concept of reverse migration adds some complexity while also increasing realism to this region's past.
Why is it realistic? Well, humans are amazingly capable of traveling great distances. We live on every continent and even those in the International Space Station are alive outside of Earth. It is common knowledge that prehistoric peoples from Siberia crossed the Bering Strait into Alaska starting around 20,000 years ago, then moved south across the Americas. Because sea levels were significantly lower at the time, hunter-gatherers could enter the new continent by crossing a frozen land bridge or by boating along its coast.
As the glaciers retreated, the Bering Sea rose and separated the two continents as the end of the last Ice Age, some 11,500 years ago. However, more immigrants kept coming, combining with and displacing earlier populations to change the genetic makeup of indigenous people in the Americas.
The remains of the three people were discovered in 2019 by archaeologists excavating a location on the banks of the Kamchatka River. Ancient DNA was extracted from the bones and examined by the experts. They discovered that these individuals were closely linked to the populations of present-day Kamchatkan. Surprisingly, though, they also carried genes that seemed to have originated from populations residing in North America.
By comparing the genomes of the trio with ancient genomes from the Asia and other parts of the Americas, the researchers created a tentative family tree. The best explanation for their history is that people crossed from Alaska back into Siberia around 5,000 years ago, and then again around 1,500 years ago, mixing with the local populations.
The frequency of these gene flow episodes during the last 5,000 years was not disclosed by the scientists. However, they can claim that there have been numerous, repeated occurrences or that it has been steady, constant, and ongoing. It's quite intriguing to consider the possibility of genetic back flow occurring over many thousands of years, rather than just once or twice.
Given the current data, repeated backflow is the most plausible scenario. However, it is not feasible to rule out the possibility that this genetic lineage originated from a prehistoric people who never left Asia but who are related to Native Americans.
The study's comparatrive analysis of more ancient genomes confirms that ancient Siberia was a human crossroads. Six ancient genomes from the Altai Mountains, dated from 5,500 to 7,500 years old. Five of the Altai hunter-gatherers were descended from a population that gave rise to a number of later groups that dispersed across the Central Asian steppe during the Bronze Age. One of the six had ancient Northeast Asian ancestry—the most western example of this lineage yet discovered—and was buried with ritualistic objects that suggested he may have been a shaman. And a 7,000-year-old person discovered close to Russia's far eastern border with China appears to have more than a quarter of their lineage from a people known as the Jōmon people who lived on the Japanese archipelago. These islands were inhabited by the Jōmon about 30,000 years ago, but the genome reveals that the islanders had at least some contact with groups on the mainland.
The authors make it very evident that there is a Jōmon-like phenomenon going on between Asia and the America, a bidirectional movement of individuals that occured over thousands of years. The work thereby improves our comprehension of how East Asian ancestry spread throughout Siberia during the Holocene.
Wang, K., Yu, H., Radzevičiūtė, R., Kiryushin, Y. F., Tishkin, A. A., Frolov, Y. V., Stepanova, N. F., Kiryushin, K. Y., Kungurov, A. L., Shnaider, S. V., Tur, S. S., Tiunov, M. P., Zubova, A. V., Pevzner, M., Karimov, T., Buzhilova, A., Slon, V., Jeong, C., Krause, J., & Posth, C. (2023). Middle Holocene Siberian genomes reveal highly connected gene pools throughout North Asia. Current Biology: CB. https://doi.org/10.1016/j.cub.2022.11.062
Flegontov, P., Altınışık, N.E., Changmai, P. et al. Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America. Nature 570, 236–240 (2019). https://doi.org/10.1038/s41586-019-1251-y