Hunter-gatherers from Mexico migrated into California more than 5,000 years ago, potentially spreading distinctive languages from the south into the region nearly 1,000 years earlier than previously thought, a new genetic study details.
The finding challenges the idea that what are known as the Uto-Aztecan languages — which include the Aztec and Toltec language Nahuatl, as well as Hopi and Shoshoni — were spread northward by prehistoric migrants from Mexico along with maize farming technologies.
"The dating and the location of this genetic material coming into California is really important for understanding the Uto-Aztecan migration," study lead author Nathan Nakatsuka, a population geneticist and a postdoctoral fellow at the New York Genome Center, told Live Science.
"We haven't fully figured it out, but we did provide evidence for a substantial migration of people coming into California at this time," he said.
The research, published on Wednesday (Nov. 22) in the journal Nature, was carried out when Nakatsuka was a student at Harvard Medical School.
Northward migration
Nakatsuka and his colleagues studied ancient DNA extracted from the teeth and bones of 79 ancient people found at archaeological sites in central and southern California. These remains were dated to between 7,400 and 200 years ago.
They also extracted ancient DNA from the remains of 40 people from sites in the northwest and central north of Mexico, which were dated to between 2,900 and 500 years ago.
By comparing the ancient genomes, the researchers found evidence for increased migration from northern Mexico into southern and central California about 5,200 years ago.
The timing of this migration refutes an existing idea that the spread of maize farming from about 4,300 years ago led to the spread of Uto-Aztecan languages, as migrant farmers prospered more than the hunter-gatherers who lived there before them. But the new study indicates that such languages may have been spread instead by a migration of hunter-gatherers that occurred nearly 1,000 years earlier.
Nakatsuka acknowledged the possibility that the later spread of maize farming into California may have been the result of the earlier migration, when the first wave of migrants were joined by related people who farmed corn by that time.
"But at the very least, we see that people are coming up here into California earlier than maize farming," he said.
Ancient California
The first people to reach the Americas arrived tens of thousands of years ago, according to the analysis of evidence found at several sites — including 14,500-year-old human poop from Paisley Caves in Oregon; 14,550-year-old artifacts from Monte Verde, Chile; and 23,000-year-old human footprints in White Sands National Park in New Mexico.
Once humans had arrived, they migrated within the Americas; and this latest study reveals a previously unknown regional migration.
The researchers also found shared genetics between the ancient peoples of California's northern Channel Islands and the adjacent coast, and the Indigenous Chumash people, whose genetics were represented by the individuals in the study who lived about 200 years ago.
Nakatsuka said that an important part of the study was obtaining ancient DNA while trying to ensure that indigenous customs, including burial practices, were respected. "We involved Indigenous groups in the conversations from the get-go," he said. "We wanted them to guide a lot of this research and have the questions that they're interested in be answered."
Robert Hard, a professor of anthropology at the University of Texas at San Antonio who wasn't involved in the research, said the study gave a deeper understanding of the relationships among different groups of Indigenous peoples.
"This study helps reject the hypothesis that ancient Uto-Aztecans brought maize into the Southwest from central Mexico and shows Uto-Aztecans were moving from Mexico into California long before maize was present," he told Live Science in an email.
He noted that the remains of many of the individuals analyzed in the study have been curated in museums in the United States and Mexico for many decades. "Now with advances in ancient DNA technology, these individuals are being given a voice through this research to help write their history," Hard said.
