By the end of the last ice age, some 14,500 years ago (and possibly long before), humans had made their way into the Americas, traversing a land mass called Beringia that bridged what is now Siberia to Alaska. These early peoples eventually became indigenous Americans, including Alaska Natives, Canadian First Nations, and Native Americans.
But many of the details of these early migrations, of which there were multiple, have remained mostly unclear—including which of the many cultural groups that once populated ancient Siberia successfully crossed the Bering Sea.
Now, findings from two new studies published today in the journal Nature may provide long-awaited clues about the mysterious ancestors of these prehistoric peoples. Though both studies leverage the power of ancient DNA to enrich the human family tree, both also raise further questions about the complex migrations that ultimately yielded modern populations.
In the first study, a team of scientists led by Eske Willerslev, a geneticist at the University of Copenhagen, attempted to pinpoint a lineage in ancient Siberia with strong genetic links to Native Americans. The researchers sequenced genomes from 34 individuals that inhabited Siberia, Beringia, and Alaska between 600 and 31,600 years ago, and compared them to DNA from modern Native Americans. The nearest match was a woman the team calls Kolyma1, who lived in northeastern Siberia some 9,800 years ago. About two-thirds of her genome bears a remarkable similarity to those of living Native Americans, making her “the closest we have ever gotten to a Native American ancestor outside the Americas,” Willerslev told Michael Price at Science.
Close to an ancestor, however, isn’t an ancestor. Most of Kolyma1’s genome technically belongs to a distinct lineage the researchers call Ancient Paleo-Siberian—and the two lines that gave rise to her people and the actual ancestors of Native Americans probably splintered about 24,000 years ago.
What’s more, the oldest samples of the bunch—two baby teeth from a site in Siberia called Yana—belong to a previously unknown population called Ancient North Siberians, who, surprisingly, have only the faintest trace of a genetic presence in modern peoples.
“[Ancestors of] Native Americans are not the first people in north-eastern Siberia as most people, if not everybody thought,” Willerslev told Nicola Davis at The Guardian.
The second study, researchers explored the roots of another population scientists call Paleo-Eskimos, thought to have arrived in America about 5,000 years ago. According to the study, these ancient people are the ancestors of a collection of Native American tribes dotting Alaska, Canada, and the Southwest who all speak a family of languages called NaDene. By analyzing the remains of 48 ancient individuals from sites spanning these regions and comparing them to the genomes of living peoples, the researchers concluded that the Paleo-Eskimo lineage split after crossing Beringia. Some of their descendants mingled with already-established indigenous Americans hailing from Siberia, yielding a line of NaDene speakers. Others, however, ventured off on their own, and may have even shuttled back and forth across the Bering Sea in subsequent years, leaving genetic heirlooms in people on both sides of the divide.
There’s still a lot left to learn about the intricacies of these early migrations—but their complexity “makes total sense,” Connie Mulligan, an anthropologist at the University of Florida in Gainesville who was not involved in the study, told Price. “There were a lot of populations migrating through the region and replacing each other, with some of them moving into the Americas.”
Motivated by food availability, changing climates, and more, ancient people took advantage of what they could, mixing everything from cultures to genes as they crossed from continent to continent. As such, the newly uncovered remains still only scratch the surface of this chapter in human history—but future searches for ancient DNA in Siberia and Alaska will hopefully fill in some of the gaps, Willerslev told Carl Zimmer at The New York Times.