From Samoa to Easter Island: DNA traces the route of the settlement of Polynesia - France 24

Paris (AFP)

Thousands of kilometers of ocean separate the populations of the Marquesas Islands, Easter Islands and Tahiti.

But they are connected by genes, reveals a study which traces, thanks to DNA, the routes of their pioneer ancestors through the vastness of the South Pacific.

Archaeologists and historians have long debated the origins of the settlement of the islands of Polynesia, a gigantic maritime area occupying a third of the Earth's surface, and one of the last habitable places to have been colonized by humans.

"This is one of the most fascinating chapters in the history of human expansion, which has left few tangible traces," Andrés Moreno-Estrada, co-author of the study published on Wednesday, told AFP. in the journal Nature.

When he explored the area at the end of the 18th century, the British captain James Cook noticed that the indigenous peoples of the Society Archipelago (including Tahiti) and of islands located more than 1,000 kilometers (called the Cook Islands by the continued), spoke the same language: Austronesian, the largest language family in the world, which has its distant origins in Taiwan.

- Incomplete puzzle -

This linguistic research, as well as the archaeological discoveries, made it possible to forge a link between these scattered populations.

But the story remained incomplete.

"No study has so far been able to locate the precise source of the first Polynesian installations", according to Andrés Moreno-Estrada, researcher at the National Genomics Laboratory for Biodiversity in Mexico City.

The tracks were blurred by too rapid expansion.

And it was ultimately by searching the DNA of current populations that the team of researchers unearthed the missing piece of the puzzle.

The first migrations in Polynesia Cléa PÉCULIER AFP

They sequenced the genome of 430 inhabitants of 21 South Pacific islands - unprecedented on such a large scale in this part of the world.

"The genomes of these island populations encoded the history of their ancestors," decrypts Alexander Ioannidis, the other co-author of the study.

"By comparing these biological signatures from one island to another, you get to know when the genomes diverged, and to estimate the moment when the populations cohabited for the last time", continues this expert in genetics from the University. from Stanford in California.

- An epic from West to East -

The results of their research draw a detailed cartography of these pioneer settlements, which goes from west to east, between the 9th and 13th centuries.

The first migrations would have left the Samoa Islands in the west, heading south-east to reach Rarotonga, the largest of the Cook Islands, around 830 AD.

Navigators would have spotted its high reliefs from afar, thanks to the clouds emitted by its volcanoes.

Near Toau atoll, in the Tuamotu archipelago, 400 kilometers from Tahiti, in October 2015 GREGORY BOISSY AFP / Archives

The migration then headed northeast, to land on the Society Islands (including Tahiti) around 1.050.

Then, around 1.110, on the Tuamotu archipelago, made up of several dozen atolls today very sparsely populated.

At the time, these islets recently emerged from the water presented arable land and young forests - in short, more favorable living conditions.

- Island giants -

The Tuamotu archipelago, which is part of French Polynesia like Tahiti, would thus have "played a decisive role in the settlement process of the South Pacific", insists Alexander Ionnidis.

"Tuamotu has a gigantic area, equivalent to that which extends from England to Greece. Its first occupants had to have a very rich maritime culture in order to be able to navigate from island to island," says Dr Ionnidis.

This technological mastery would have allowed navigators to venture later thousands of kilometers away.

It is also from Tuamotu that the study sets out the more distant migrations that followed: some to the North, to the Marquesas Islands, others to the East, via Mangareva (archipelago of the Gambier Islands) in the 12th century. century, to end at the eastern end, Easter Island.

"This study is a genetic feat which makes it possible to draw a hyper refined scenario" of this epic, rejoiced Florent Détroit, paleoanthropologist at the National Museum of Natural History in Paris, who did not participate in the research.

These genetic matches go in the same direction as the archaeological discoveries, notes this French researcher.

And the study hypothesizes that the large megalithic constructions - the giants of Easter Island, the "tiki" statues of Raivavae and those of the Marquesas - all bear a common ancestral signature, coming from the Tuamotus.

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