Kumara origin points to pan-Pacific voyage

Genetics have finally nailed one of the great South Pacific mysteries – where did pre-historic Polynesians get kumara from.

Research published today in the Proceedings of the National Academy of Sciences shows what many Polynesians always believed – the ancient voyagers went to South America and got it, long before Europeans even reached the South Pacific.

The kumara, or sweet potato (Ipomoea batatas), was domesticated in Peru about 8000 years ago and slowly spread through South America.

But how it got the 5000km to Polynesia has been the source of endless argument, including the famed, but ultimately wrong 1947 Kon-Tiki expedition in which Norwegian explorer Thor Heyerdahl tried to show native Americans took kumara to Polynesia.

According to Science Now, archaeologists and linguists have accumulated evidence supporting the hypothesis that pre-modern Polynesian sailors went to South America and picked up sweet potato.

Running DNA tests have proven difficult because European traders exported varieties of sweet potato from Mexico and the Caribbean to the Pacific, and those breeds mixed with the older Polynesian varieties.

But in research published today a team of researchers working with France's Centre of Evolutionary and Functional Ecology and CIRAD, a French agricultural research and development centre, say they have found samples of sweet potato that were picked up before the European exports from South America.

Early European explorers picked up plant samples and took them back to Europe.

Science Now says that by analyzing genetic markers specific to sweet potatoes in both modern samples of the plant and older herbarium specimens, the researchers discovered significant differences between varieties found in the western Pacific versus the eastern Pacific.

This supports the idea the “tripartite hypothesis; the plant arrived first by Polynesians themselves, then by Spanish traders sailing west from Mexico, and Portuguese traders coming east from the Caribbean.

Lead author Caroline Roullier says that although her genetic analysis alone doesn't prove that premodern Polynesians made contact with South America, it strongly supports the existing archaeological and linguistic evidence pointing to that conclusion.

‘‘It's the combination of all different kinds of proof" that's really convincing, she said.

Anthropologist Sir Peter Buck in his 1954 Vikings of the Sunrise argued strongly that Polynesians had gone themselves to get kumara.

In 2008 biological anthropologist Dr Elizabeth Matisoo-Smith of the University of Auckland, along with GNS Science in Wellington, dated chicken bones found in Chile.

They found that they pre-dated the arrival of the Spanish, but they were from Polynesia.

It suggested that Polynesians had sailed with chickens, reached a place in south-central Chile and had traded them for kumara.

The chicken traders were from Eastern Polynesia and were definitely not New Zealand Maori; in pre-European times they did not have chickens. They are likely to have come from what are now the northern Cook Islands.

Various researches have also shown that the Polynesian came home with more than kumara; that are hints that some brought indigenous American women home too.