When European explorers first reached Rapa Nui, a remote island in the south Pacific Ocean, in the 1700s, they encountered a small community of about 3000 people living among giant stone statues and stone platforms. Anthropologists later concluded that ancient, much larger populations on what Europeans called Easter Island had built the statues, called mo’ai, and had used up the island’s resources to do so, resorting to violence and cannibalism before European arrival. This narrative of ecological and population collapse became a cautionary tale of overexploitation of resources, popularized by University of California (UC), Los Angeles biologist Jared Diamond in his book Collapse: How Societies Choose to Fail or Succeed.
Now, the first study of the genomes of ancient Rapanui, published today in Nature, shows such a population collapse never happened. The finding reinforces previous archaeological evidence, including a study in July, suggesting the island was never heavily populated. “Working with Indigenous groups, we face so many tropes and outdated narratives that people keep perpetuating—even scientists,” says Kathrin Nägele of the Max Planck Institute for Evolutionary Anthropology, who wrote an accompanying commentary for Nature. “I hope this … ancient DNA [study] puts the last nail in the coffin of this [collapse] narrative.”
The notion of an ecological suicide, or “ecocide,” was based on the fact that explorers found the island mostly deforested, and the big native animals gone. Some archaeologists also interpreted obsidian spear points as a sign of past civil war. But Víctor Moreno Mayar, an evolutionary geneticist at the Globe Institute of the University of Copenhagen, realized ancient DNA from the islanders could provide more direct evidence of past population bottlenecks.
The researchers asked to study remains on the island. But the Rapanui community couldn’t reach consensus. The team turned to the Museum of Man in Paris, which houses the remains of 15 individuals labeled as Rapanui and collected by European ethnologists in the 1870s and 1930s. The community supported that study, saying that if DNA showed the remains were Rapanui, islanders would be interested in repatriation.
In late 2019, the team sampled four teeth and a bit of the DNA-rich petrous bone—part of the skull right behind the ear—of 11 individuals. They extracted DNA and sequenced the whole genomes. The DNA confirmed the individuals were most closely related to modern-day Rapanui.
The Rapanui consented to additional research, saying the most important question for them was whether the collapse narrative was true, Moreno Mayar says. “Everyone in the community was involved and [the researchers] were open to questions, so it was quite interactive,” says archaeologist Gabriela Atallah Leiva, a curator at the MAPSE Rapa Nui Museum in Hanga Roa.
“Archaeogenetics has more perpetuated colonial injustices than tried to get rid of them,” Nägele says. “I’m very happy … the authors went to the communities and asked [for] their consent.”
The whole-genome data allowed the researchers to search for signs of bottlenecks, which leave low diversity in the genomes of descendants. They saw evidence of only one, very ancient bottleneck, likely due to the founding event of the island before 1300 C.E.—a finding supported by other researchers’ analysis of DNA from modern Rapanui. Moreno Mayar’s team estimates the population grew slowly but steadily after it was founded. Historical records show European contact did lead to population crashes: Peruvian slave raiders kidnapped one-third of the population in the 1860s and disease outbreaks left only about 110 individuals by the 1870s. “After the arrival of the Europeans, the history of Rapa Nui is dark,” Moreno Mayar says.
The new results “deliver solid data that the ‘ecocide’ hypothesis is not supported,” says Lars Fehren-Schmitz, an anthropological
geneticist at UC Santa Cruz.
Diamond and others had argued the Rapanui felled so many logs to move the mo’ai that they deforested the island and eroded the soil, leaving the island unable to sustain its original population, which they estimated at about 15,000. But archaeologists had already begun to dismantle that narrative. Most recently Carl Lipo, an archaeologist at Binghamton University, and his team used satellite imagery and machine learning to map the island’s rock gardens, a method of spreading rocks to improve soil productivity. In a paper in Science Advances in July, they concluded Rapa Nui’s agriculture was far less extensive, and its population smaller, than the “ecocide” theory had proposed. Although the ancient Rapanui did cut down most of the island’s trees, the deforestation did not trigger a cultural or population crisis, they say. “Their ability to adapt was successful,” Atallah Leiva says.
The new DNA findings are “fantastic,” Lipo says, and “spectacular for us because it provides independent evidence of what we’ve been arguing based on archaeology.”
Diamond, however, told Science he remains unconvinced by the computer models the geneticists used to estimate past population sizes. And despite the DNA results, he questions whether the remains are good stand-ins for ancient Rapanui, because they apparently date to after European contact.
In a bonus from the work, the team found that Native American DNA comprised up to 12% of the ancient people’s genomes. That finding supports earlier hints that Polynesian Rapanui mixed with Native Americans from South America some 600 to 800 years ago, perhaps by making round-trip voyages to the South American coast. The sweet potato, which was domesticated in the Andes, was a staple of Polynesian cuisine long before European contact; and chicken bones from Polynesian lineages that predate European colonization have been found at South American archeological sites.
The research results, shared with locals, have already had an impact on the Rapanui, Moreno Mayar says; the team is planning museum posters and a short film. He says the community is “open to all of these new ideas.” The next step is for the ancient Rapanui remains stored in Paris to be returned to the island, according to Moreno Mayar.
“Recovering all ancestors is the priority,” Atallah Leiva confirms. “For the Rapanui culture, the ancestors are here among us … they are not in the past, they are here in the present.”
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