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The Norwegian explorer and ethnographer Thor Heyerdahl, which traveled some 8,000 km across the Pacific Ocean in 1947 aboard a handmade raft on the Kon-Tiki expedition, suggested that the prehistoric populations of South America played an important role in the settlement of eastern Polynesia and particularly on Easter Island.
But until now this daring hypothesis had remained as controversial as it was at the time it was proposed because molecular genetic studies had reached opposite conclusions.
In the absence of scientific evidence, the origin of the population of this Pacific island has remained for decades one of the most unknown chapters in human history.
A team led by the National Genomics Laboratory for Biodiversity (LANGEBIO) of the Center for Research and Advanced Studies of Mexico (Cinvestav) has now found the genetic evidence to decipher this prehistoric event that left no conclusive trace. "This is the fingerprint registered in the DNA of those who had contact 800 years ago in one of the most remote places on the planet," Andrés Moreno-Estrada, a LANGEBIO researcher, explains to SINC.
The results, published this week in the journal Nature, thus support the hypothesis of a prehistoric contact between Native Americans and Polynesian settlers long before the arrival of European explorers to this area of the Pacific Ocean, but they also contribute “Additional never-before-revealed details like the date, origin and destination of the contact”, Emphasizes Moreno-Estrada.
“The oldest chromosomal segments of American origin found in Polynesian settlers date back approximately 800 years and the closest genetic affinity of these ancestral segments was observed with indigenous populations that currently inhabit the Colombian region of the Pacific coast. Thus, we believe that the population that made contact could have originated near the coasts of Colombia or Ecuador ”, underlines the main author of the work.
A single contact in the Pacific
This genetic mix is not only observed in Rapa Nui, but also in other remote islands of Polynesia: Marquesas del Norte, Marquesas del Sur, Mataiva and Mangareva. As Easter Island was the last to be populated, according to archaeological records, researchers believe that contact must have occurred at some point prior to the arrival of its first settlers, favored by the equatorial marine currents from America to the South Pacific. .
"With current data, we cannot definitively rule out an event in the opposite direction, in which Polynesian sailors have reached America and returned to the Pacific islands," says Andrés Moreno-Estrada.
Thus, for the research team, among which scientists from the universities of Stanford (USA), Oxford (UK) and Chile, among others, have participated, the genetic contribution is probably derived from a single prehistoric contact of indigenous people Americans at some point in Polynesia that dispersed the American DNA to these islands.
"The average contribution of this ancient event in the current inhabitants of these islands is around 5% and is different from the abundant recent contribution of Mapuche genes that Easter Island has experienced since its annexation to Chile since 1888", emphasizes the Mexican researcher .
The researchers analyzed the genomes of more than 800 individuals from 32 different populations, among indigenous groups along the American Pacific coast and inhabitants of the islands of the South Pacific. For all of them, more than 800,000 genetic positions were analyzed using massive genotyping platforms of the entire genome. They also sequenced the complete genomes of 10 individuals of Polynesian origin at the Cinvestav laboratory facilities in Mexico.
"If it were not for technological advances and computational methods to analyze genomes with complex degrees of ancestral mixtures, it would not have been possible to answer a question that for decades has been approached from multiple disciplines," concludes the project leader, for whom it is necessary make more efforts in genomic research of Latin American populations.
Reference: Alexander G. Ioannidis et al. "Native American gene flow into Polynesia predating Easter Island settlement" Nature July 8, 2020.