Genetics Reveal How Humans Hopped From Island To Island To Settle In Remote Pacific | Genetic



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The famous megaliths of Easter Island have relatives on islands thousands of miles north and west, just like the people who created them, according to a study.

Over a period of 250 years, distinct groups of people moved from tiny islands east of Tahiti to settle on Easter Island, the Marquesas and Raivavae – archipelagos thousands of miles apart but all home to similar ancient statues.

“These statues are only found on islands which are closely related genetically,” lead study author Alexander Ioannidis of Stanford University told AFP.

Ioannidis and his team were able to map and date the Polynesians’ earliest settlement path, which began in Samoa and spread across the Pacific between the 830s and 1360s, using cutting-edge modern DNA analysis. .

“It was an open issue since Captain Cook first noticed that the people of the Polynesian islands all speak the same language,” Ioannidis said.

The expansion occurred rapidly – over about 17 generations – overtaking major changes in language or culture that could have served as markers, the results show. The researchers were able to piece together the puzzle of trans-Pacific migration by comparing the genetic material of 430 current inhabitants of 21 islands.

The outward expansion of Samoa was west to Fiji, Tonga to the south, then east to Rarotonga around AD 830.

A few hundred years later, descendants of Rarotonga traveled to settle in Tahiti and the Tuamotu archipelago just beyond. It is from the small, long-neglected sandbank islands of the Tuamotus that the most ambitious forays have started, Ioannidis said.

Now sparsely populated, in part thanks to their role as a nuclear testing ground, the Tuamotus extend over an area equal to the distance between England and Greece.

The study notes that the low lying islands most likely emerged from below sea level just a few hundred years before the Polynesians spread there.

“They had to have a maritime culture to move between these little ring-shaped islands,” Ioannidis said. “I think that partly explains why this is where we see the longest trips from.”

It has become the zero point for the megalith-building peoples who came to live in the Marquesas, Rapa Nui (Easter Island) and Raivavae.

The timing of these expansions matches earlier DNA-based discoveries from Ioannidis and his team showing that Native Americans – likely from the northwest coast of South America – and Polynesians intermingled around AD 1200 .

“The date we found for this contact is very close to the dates we find for these trips from the Tuamotus to colonize these remote islands,” Ioannidis said.

Today’s Polynesian populations have a mixed heritage, with traces of Europe, Africa and other places in their ancestry.

While genetic studies of ancient people tended to focus on ancient DNA samples unearthed at archaeological sites, Ioannidis said his team was able to focus on telltale sequences buried in modern DNA.

They used software to analyze samples of 430 inhabitants on 21 different islands to identify recurrent gene patterns specific to Polynesians, blocking DNA sequences associated with European or other ancestry.

Otherwise, “you would just find that the islands with the ‘more Polynesian’ DNA were more related,” Ioannidis said. “It’s not historically interesting.”

His team used the genetic clues to draw a sort of family tree from east to west across the Pacific.

The DNA strands get shorter as they are recombined over generations, so the length of the shared segments revealed how many generations have passed between each colony.

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