• The Star Staff

Some Polynesians carry DNA of ancient Native Americans, new study finds



By Carl Zimmer


About 3,000 years ago, people on the eastern edge of Asia began sailing east, crossing the ocean to reach uninhabited islands. Their descendants, some 2,000 years later, invented the double-hulled canoe to reach places like Hawaii and Rapa Nui.


Archaeologists and anthropologists have long debated just how far the Polynesians’ canoes took them. Did they make it all the way to the Americas?


The results of a new study suggest that they did. Today, people on Rapa Nui, also known as Easter Island, and four other Polynesian islands carry small amounts of DNA inherited from people who lived in Colombia about 800 years ago. One explanation: Polynesians traveled to South America, and then took South Americans onto their boats to voyage back out to sea.


This new report bolsters work that archaeologists and anthropologists have been doing for years. Previous genetic studies had also hinted that people on Rapa Nui had some ancient South American ancestry. But the new study offers a more compelling case because the researchers looked at more than 800 people using a number of sophisticated new statistical tools.


“This is the most convincing evidence I’ve seen,” said Lars Fehren-Schmitz, an anthropological geneticist at the University of California, Santa Cruz, who was not involved in the study.


The new study emerged from a decadelong project to create a map of the genetic diversity in modern Latin Americans. After Asians crossed the Bering Land Bridge 16,000 years ago, they spread across the Americas, reaching the southern tip of South America by 14,000 years ago.


Since then, the populations of Latin America have gained unique genetic mutations, which have gotten mixed as they interbred. When European colonists brought African slaves to the region, the genetic landscape of Latin America changed again.


Andrés Moreno Estrada, a geneticist, and his wife, Karla Sandoval, an anthropologist, have worked with Indigenous populations in Latin America to understand their genetic makeup.


Estrada and Sandoval traveled to Rapa Nui and met with residents to describe their project.


Eighty islanders eventually joined the research, curious to learn about their ancestry. “They were interested to know if they really belonged to the Polynesian islands,” said Sandoval, who works with Estrada at the National Laboratory of Genomics for Biodiversity in Irapuato, Mexico.


In an earlier study on Rapa Nui, led by Anna-Sapfo Malaspinas of the University of Lausanne, researchers analyzed DNA from 27 islanders. They found evidence that the participants had a mixture of Polynesian and Native American ancestry.


Some of their Native American DNA appeared to have been inherited by recent immigrants from Chile. But other pieces were different, suggesting they originated from Native Americans many generations earlier.


To test that finding, Estrada, Sandoval and their colleagues compared the DNA of 809 people from Rapa Nui and other Polynesian islands, as well as in countries along the Pacific coast from Mexico to Chile.


The researchers found that most of the people on Rapa Nui had some recent Chilean forebears. From them, they inherited both Native American and European DNA.


But six people had no European ancestry. Their Native American ancestry had a different source: the Zenu population of Colombia. The scientists then found some of the same pieces of DNA in people on four other islands in eastern Polynesia.


“When I first saw that, I thought there was something going wrong and we needed to fix what we were doing,” said Alexander Ioannidis, a postdoctoral researcher at Stanford University and a co-author of the study. “So then we dove in deeper. It took a while to really realize that this was real.”


The researchers were then able to estimate how long ago these Native American ancestors lived by measuring the size of the DNA fragments. Stretches of shared DNA get smaller with each passing generation.


The researchers found that all of the Zenu-like stretches of DNA in the Polynesians were roughly the same size. They estimated that they came from Zenu relatives who lived about eight centuries ago.


“It’s quite amazing that they can come up with this evidence for contact between these populations,” Malaspinas said.


Lisa Matisoo-Smith, a biological anthropologist at the University of Otago in New Zealand who was not involved in the new study, cautioned that the history of Polynesia was so complex that the new results might not reflect it accurately.


“Is it possible? Yes, it certainly is,” she said. But, she added, “I’m not convinced.”


Malaspinas said that since Polynesians had already traveled so far across the Pacific, there was no reason to think they couldn’t go to South America. “This last step would have been easy for them,” she said.


Patrick Kirch, a University of Hawaii archaeologist, said that this fit with other lines of evidence, including the food that Polynesians eat.


A staple across Polynesia is the sweet potato, which originated in South America. Kirch and his colleagues have found remains of sweet potatoes centuries before Europeans arrived in the Pacific.


But the authors of the new paper emphasize another possibility: South Americans traveled on their own to a Polynesian island, where Polynesians sailing from the east encountered them.


In their paper, Estrada and his colleagues draw parallels between this scenario and the claims of Thor Heyerdahl, the Norwegian explorer who sailed on a raft in 1947 from South America to Polynesia. Heyerdahl championed the idea that Polynesia was settled by South Americans.

In an email, Haunani Kane, a postdoctoral research fellow at the University of Hawaii, criticized the scientists for championing such “outdated” ideas.


Kane has sailed thousands of miles in double-hulled canoes as the scientific coordinator of the Polynesian Navigation Society. She took issue with “the author’s assumption of the capabilities or lack thereof, of Pacific Island peoples to purposely migrate across the Pacific.”


Kirch also dismissed the castaway scenario. If South Americans wound up on the Marquesas Islands, they would have brought some things with them that archaeologists could have later uncovered. “There’s no evidence of that,” he said.

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