How did Native American DNA reach Polynesia centuries before Europeans crossed the Pacific?

A 2020 study published in Nature analyzed 807 individuals from 17 Polynesian island populations and 15 Native American groups from the Pacific coast of the Americas.

The researchers found conclusive genetic evidence that Polynesians and Native Americans came into contact around AD 1200, during the period when remote eastern Polynesia was being explored and settled.

Importantly, the evidence suggests that this contact happened before the settlement of Rapa Nui. Rather than originating on Easter Island itself, the Native American ancestry found there was probably inherited from an earlier contact somewhere else in eastern Polynesia.

The American ancestry was most closely related to Indigenous populations from present-day Colombia and Ecuador, particularly the Zenu population from Colombia.

Genetic dating produced remarkably similar estimates across several islands: around AD 1150 in the South Marquesas, AD 1200 in the North Marquesas, and AD 1230 in both Mangareva and Palliser. A separate method estimated the shared admixture event at AD 1234 ± 90 years.

The earliest signal comes from Fatu Hiva in the South Marquesas. Because this date is close to the estimated initial Polynesian settlement of the Marquesas, the authors raise an intriguing possibility: Polynesian settlers may have encountered a small Native American population already living there.

However, the DNA cannot determine the direction of the original voyage. Native Americans may have crossed the Pacific to Polynesia, but Polynesian voyagers could instead have reached northern South America and returned with Native American people or ancestry.

The study ultimately favors a single prehistoric contact event somewhere in eastern Polynesia. Descendants carrying both Polynesian and Native American ancestry may then have spread across other islands, leaving a genetic signal in the Marquesas, Palliser, Mangareva and eventually Rapa Nui.

📚 Source: Ioannidis et al. (2020), Native American gene flow into Polynesia predating Easter Island settlement, Nature 583, 572–577.

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