DNA offers surprises on how Polynesia was settled

By | September 22, 2021

Science reports:

The peopling of Polynesia was a stunning achievement: Beginning around 800 C.E., audacious Polynesian navigators in double-hulled sailing canoes used the stars and their knowledge of the waves to discover specks of land separated by thousands of kilometers of open ocean. Within just a few centuries, they had populated most of the Pacific Ocean’s far-flung islands. Now, researchers have used modern DNA samples to trace the exploration in detail, working out what order the islands were settled in and dating each new landfall to within a few decades.

“The whole question of the settlement of Polynesia has been going on for 200 years,” says University of Hawaii, Manoa, archaeologist Patrick Kirch, who was not involved in the research. “This is a really great paper, and I’m happy to see it.”

Archaeologists already had hints of how this great exploration took place. Studying the styles of stone tools and carvings, as well as languages, of the people on the various islands had suggested the original ancestors traced back to Samoa and that the expansion ended halfway across the ocean in Rapa Nui, or Easter Island. But they disagreed on whether it happened in a few centuries, beginning around 900 C.E., or started much earlier and lasted 1 millennium or more.

To learn more, Stanford University computational geneticist Alexander Ioannidis and Andrés Moreno Estrada, a population geneticist at Mexico’s National Laboratory of Genetics for Biodiversity, compared the DNA of 430 modern individuals from all across Polynesia (most collected for previous studies), and then eliminated later genetic input from European people. Because the researchers knew Polynesians had journeyed stepwise from island to island, their genetic analysis utilized a genetic phenomenon known as a population bottleneck. When a few dozen to a few hundred individuals from already-isolated island populations settled a new island, and then a subset of that group left to settle an additional island, and so forth, their genetic diversity would have shrunk with each voyage—like a telescope in reverse. [Continue reading…]

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