Wednesday, November 28, 2007

Polynesians were in Americas, but left no clear genetic trace

An extensive survey of the genetic makeup of native Americans—north and south—show no markers to indicate Polynesians contributed significantly.

That doesn't mean early Pacific voyagers didn't visit the western coasts of the Americas. There is evidence they did. But it suggests they didn't stay, or at least didn't stay in significant enough numbers to leave a genetic footprint.

(Photo: The Hawaiian-designed voyaging canoe Alingano Maisu, at the dock at Kawaihae, Hawai'i, before crossing the Pacific this year, showing that Polynesian canoes and crews were fully capable of accurate long-distance voyaging. Jan TenBruggencate photo.)

“From these analyses, there is no compelling evidence for a Polynesian contribution to South American genetic variation.

“I am unable to say whether there was admixture that was too limited to be detected by our analysis,” said Cecil M. Lewis Jr., an anthropologist at the University of Oklahoma.

He is one of the main authors of a massive scientific endeavor, which looked at genetic material from native Americans from the Arctic down the southern point of South America, and from the Atlantic to the Pacific.

The paper, “Genetic Variation and Population Structure in Native Americans,” was published this month in the online scientific journal PloS Genetics. The other primary authors are Sijia Wang of University College London's Galton Laboratory, and Mattias Jakobsson, of the University of Michigan's Department of Human Genetics. Two dozen other researchers from around the world also participated.

They took genetic samples from 422 individuals in 24 American native ethnic groups, and conducted detailed studies.

Among their conclusions:

► The Americas were most likely populated in a single colonization event from Siberia across a land bridge through the Bering Strait area. “The lower level of genetic diversity observed in the Americas compared to other continental regions is compatible with a reduction in population size associated with a geographically discrete founding,” the authors wrote.

► But while that's the best guess, “similar patterns could result from gene flow across the Bering Strait in the last few thousand years, together with continual interactions between neighbors on both sides of the Bering Strait.”

The people of the early Americas are clearly related: “at each step in the migration, a subset of the population splitting off from a parental group moves deeper into the Americas, taking with it a subset of the genetic variation present in the parental population.”

► The habitation of the Americas started down the oceanic coasts, and moved inland later. The western (Pacific) coast of South America was populated before the eastern and Amazon basin areas.

As you might expect, groups of native Americans with similar languages are generally similar genetically.

Does this work refute suggestions that Polynesians made contact with the Americas? Certainly not. It simply says that Polynesians didn't contribute a great deal to the genetic makeup of the American natives.

Other genetic work shows that Polynesian settlement occurred generally from west to east across the Pacific.

Within the past year, researchers have published genetic work indicating that the chickens found in coastal sites in Chile were the same as the chickens the Polynesians carried across the Pacific. It was the first hard evidence of a Polynesian “thing” in the Americas.

Previously, the American sweet potato has been located throughout the Pacific, but there was no clear proof of how it got there.

Increasingly, the evidence is that Polynesians were such remarkable ocean voyagers that they could readily have conducted back-and-forth voyages across great distances throughout the Pacific.

The most recent evidence of such voyaging was an adze found in the Tuamotu Archipelago, which was made of stone quarried on Kaho'olawe Island in the Hawaiian Archipelago. First, Polynesians needed to voyage to Hawai'i, in the North Pacific, from their South Pacific origins, and then, they had to sail back to deliver the adze stone.

The chickens appear to be proof of at least one voyage east to the Americas, and the sweet potato increasingly appears to be proof of voyaging back west from the Americas. The Kaho'olawe-Tuamotu adze appears to be proof of at least one voyage north to Hawai'i and then south to the Tuamotus.

Future archaeological and genetic work will doubtless provide further proof of frequent voyaging.

One thing the Wang-Lewis-Jakobsson genetic work, combined with other recent work, suggests is that while Polynesians were great voyagers, they tended not to settle in areas that were already inhabited.

© 2007 Jan W. TenBruggencate

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