Technology & Science

Polynesian and South American people met, procreated many centuries ago

Centuries before Europeans reached the Americas, two groups of people separated by 6,800 kilometres of ocean met, exchanged sweet potatoes — and made babies together, a new study confirms.

People 6,800 kilometres away by sea share DNA, showing they had children together 800 years ago

The sun rises on Easter Island, one of several islands where Polynesian people's DNA showed ancestry from South America. (Andres Moreno-Estrada)

New genetic research shows that there was mingling between ancient Indigenous peoples from Polynesia and South America, revealing a single episode where they procreated together roughly 800 years ago after an epic transoceanic journey.

The question of such contact — which was long hypothesized, in part based on the enduring presence in Polynesia of a staple food in the form of the sweet potato that originated in South and Central America — had been keenly debated among scientists.

Scientists said on Wednesday an examination of DNA from 807 people — from 14 Polynesian islands and Pacific coastal Indigenous populations from Mexico to Chile — definitively resolved the matter.

People from four island sites in French Polynesia — Mangareva and the Pallisers in the Tuamotu Archipelago and Fatu Hiva and Nuku Hiva in the Marquesas Islands — bore DNA indicative of procreation with South Americans most closely related to present-day Indigenous Colombians around 1200 AD.

These islands are roughly 6,800 kilometres from South America.

People from Chile's Rapa Nui, or Easter Island, also had South American ancestry, some from modern Chilean immigrants and some from the same ancient intermingling as the other islands. Rapa Nui, located 3,700 kilometres west of South America and known for its massive stone figures (called moai), was settled some time after the intimate contact 800 years ago.

But who made the crossing?

The study left open the question of who made the monumental Pacific crossing — Polynesians heading east and arriving in Colombia or perhaps Ecuador, or South Americans travelling west.

"I favour the Polynesian theory, since we know that the Polynesians were intentionally exploring the ocean and discovering some of the most distant Pacific islands around exactly the time of contact," said Stanford University computational geneticist Alexander Ioannidis, lead author of the research published in the journal Nature.

"If the Polynesians reached the Americas, their voyage would likely have been conducted in their double-hulled sailing canoes, which sail using the same principle as a modern catamaran: swift and stable," Ioannidis added.

This contact explains the mystery of how the sweet potato arrived in Polynesia centuries before European sailors. Ioannidis noted that the sweet potato's name in many Polynesian languages — kumara — resembles its name in some Indigenous Andes languages.

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