Indigenous peoples descend from ancestral groups that diverged tens of thousands of years ago then later re-reconnected, according to a new study.

Based on the DNA of 91 ancestors in the United States and Canada, researchers believe a split occurred about 18,000 to 15,000 years ago in the Americas. One group, labeled ANC-A, corresponds to those who traveled south, likely along the Pacific coast, while a second, labeled ANC-B, kept north and also headed east toward the Great Lakes region.

The divergence shows up in the descendants of the two groups, according to the genetic results. Yet comparisons to the DNA of 45 present-day Native peoples from Central and South American indicate there are populations with a mixture of ANC-A and ANC-B as far away as Chile.

“This cannot be explained by activity in the last few thousand years. It is something altogether more ancient,” Toomas Kivisild, a co-senior author of the study, said in a Cambridge University press release

Previously, researchers thought the first Americans descended from one ancestral group. That theory was primarily based on archaeological rather than genetic studies.

“We are starting to see that previous models of ancient populations were unrealistically simple,” University of Illinois anthropology professor Ripan Malhi. said in a press release

Christiana Scheib, the first author of the study, reached out to tribal communities as part of the effort. She talked to indigenous peoples in California, where the ancestral remains came from the Channel Islands

"The lab-based science should only be a part of the research," Scheib said. "We need to work with Indigenous communities in a more holistic way."

According to The New York Times, a Native boy who lived in Montana about 13,00 years ago belongs to ANC-A. His DNA was studied with tribal blessings and was found to be related to present-day Native peoples.

The Kennewick Man, whose DNA was studied without tribal approval, belongs to ANC-B, according to The Times. He also was related to present-day Native peoples , with his closest living relatives found among citizens of the Colville Tribes in the Northwest.

Present-day Native peoples and their ancestors In Ontario, Canada, also belong to ANC-B. The modern descendants are speakers of Algonquin languages, according to The Times and The Atlantic.

The DNA from the Channel islands ancestors was found to be 58 percent ANC-A and 42 percent ANC-B, The Times reported. Mixtures of both groups were also seen in indigenous populations in South America, according to the results.

"It appears that a genetic split and population isolation likely occurred during the Ice Age, but the peoples remixed at a later date," the abstract of the study, which was published in the journal Science on Thursday, reads.

The Channel islands fall within the homelands of the Chumash people and the Tongva people. At least one other tribe has claimed affiliation with the islands as well.

A study of boulders and bedrock in the islands of Alaska’s Alexander Archipelago uncovered a potential migration route for the first Americans. Photo: Jason Briner

A different study published in the journal Science Advances on Wednesday also looked at ancestral Americans. According to the results, coastal areas in Alaska that were previously covered by ice cleared up around 17,000 years ago, offering a potential migration route.

“There was a coastal route available, and the appearance of this newly ice-free terrain may have spurred early humans to migrate southward,” Alia Lesnek, the study's first author, said in a University of Buffalo press release

The study was based on an analysis of boulders and bedrock from islands in southeastern Alaska, home to the Haida, Tlingit and Tsimshian peoples.

Read More on the Story: The Great Breakup: The First Arrivals to the Americas Split Into Two Groups (The New York Times May 31, 2018) The Increasingly Intricate Story of How the Americas Were Peopled (The Atlantic May 31, 2018) And two became one: ancient American lineages reunited to head south (Cosmos Magazine June 1, 2018)

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