Ellen Phiddian
Cosmos science journalist
A study of ancient DNA has thrown a popularly held belief about Rapa Nui, or Easter Island, into even more doubt.
It’s also provided evidence that the people who inhabited the remote island had contact with Indigenous people in the Americas, more than 3,500km away.
The study, done by an international team of researchers, is published today in Nature.
Rapa Nui is frequently used as a cautionary tale – it’s been widely believed that the people who inhabited the remote island caused their own population to collapse through deforestation in the 1600s.
“The idea of a self-inflicted Rapanui population collapse due to resource overexploitation during the 1600s is quite ingrained even in popular culture,” the lead researchers Assistant Professor Víctor Moreno-Mayar, Bárbara Sousa da Mota and Associate Professor Anna-Sapfo Malaspinas explained to Cosmos via email.
“However, there is a large body of archaeological and anthropological data that contradicts the theory.”
The dubious tale has been dubbed the “ecological suicide” or “ecocide” theory.
While it’s clear the Rapanui did change the ecology of the island dramatically, and there were about 1,500-3,000 people living there upon European contact in 1722, evidence that the population was much higher a century earlier is far murkier.
It’s also disputed whether the Rapanui made contact with people in the Americas, after their arrival on the island in about 1250 CE.
Even today, Rapa Nui is one of the most isolated inhabited places in the world, nearly 2,000km from the closest populated island.
What is clear is that the Rapanui people did suffer huge population losses after European contact, from direct killing, slave raiding and the introduction of new diseases. The population fell to roughly 110 individuals in the 19th century.
In this study, the researchers examined the DNA of 15 ancient Rapanui individuals, who according to carbon dating lived from 1670-1950.
The remains of these people are currently housed at the Musée de l’Homme, France, and the team is now discussing repatriation with the modern Rapanui community.
“From the technical perspective, working with ancient DNA is always very challenging because it is usually degraded, chemically damaged and prone to contamination with present-day DNA,” Moreno-Mayar, who is from the University of Copenhagen in Denmark, and Sousa da Mota and Malaspinas, who are from the University of Lausanne in Switzerland, tell Cosmos.
The researchers prevent contamination with dedicated clean lab facilities, and were able to assemble whole-genome sequences for each of the individuals.
“In general, the data turned out to be of very high quality and thanks to this we were able to conduct a number of analyses that are harder to implement using the kind of data that is more widespread in the field of ancient human DNA,” say the researchers.
The team examined the genomes for clues like sudden drops in genetic diversity, which would imply a population collapse.
“When we started working with the data, we were not sure about what we were going to find,” they explain.
“In the end, we find no evidence of a dramatic population decline as per the collapse idea. This genetic result seems consistent with the wealth of hard evidence provided by other fields for debunking the collapse theory.”
Moreno-Mayar believes that the ecocide idea is “part of a colonial narrative”.
“That is this idea that these supposedly primitive people could not manage their culture or resources, and that almost destroyed them. But the genetic evidence shows the opposite,” says Moreno-Mayar.
The team also looked for evidence of DNA from Indigenous American populations, which would suggest that Rapanui people had contact with them. Previous research on mitochondrial DNA has found no evidence of this.
But in this data, the team found that ancient and present-day Rapanui both had about 10% of their DNA from Indigenous Americans.
“We looked into how the Indigenous American DNA was distributed across the Polynesian genetic background of the Rapanui. This distribution is consistent with a contact occurring between the 13th and the 15th centuries,” says Moreno-Mayar.
“While our study cannot tell us where this contact occurred, this might mean that the Rapanui ancestors reached the Americas before Christopher Columbus,” says Malaspinas.
“We believe this means that Rapanui were capable of even more formidable voyages across the Pacific than previously established,” adds Sousa da Mota.
Alongside contributing to repatriation efforts for the Rapanui, the team is now hoping to learn more about the peopling of the Pacific.
“There are many other questions that call for research, for example, the fine details about the evolutionary relationships between the Rapanui and other Polynesian islanders, the number and direction of transpacific contacts and nailing down the Indigenous American populations that were in contact with Polynesians,” the researchers tell Cosmos.
“The whole model of ecocide and societal collapse has also been questioned by Pacific scholars, based on a range of archaeological evidence,” says Dr Lisa Matisoo-Smith, a professor of biological anthropology at the University of Otago, New Zealand, who was not involved in the research.
“But now, we finally have ancient DNA evidence that directly addresses these two questions and perhaps will allow us to focus on a more realistic narrative of the history of this intriguing, yet actually rather typical, Polynesian island.”
Dr Phillip Wilcox, an associate professor in quantitative genetics also at the University of Otago, who also wasn’t involved in the research, says that the study provides “strong evidence” to dispel the ecocide theory, and commends the researchers for consulting with local Rapanui community to ensure the study was conducted appropriately.
“The research team is to be commended for their efforts to ensure the research does not perpetuate further harms to the community being studied – as has happened multiple times in the past in genetics-based investigations,” says Wilcox.
But he adds that a limitation of the study is that it relies “entirely on technologies of modern science, without substantive inclusion of traditional knowledge from indigenous Eastern Polynesians”.
“This study – along with previously published genetic sciences-based research showing evidence of native American ancestry in Polynesians – could have been strengthened by inclusion of indigenous knowledge and a more comprehensive understanding of the histories of Eastern Polynesian peoples,” says Wilcox.
