The Sweet Potato Proves the Polynesians Reached the Americas

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The Polynesians travelled the vast Pacific in outrigger canoes.

For a long time, anthropologists have been debating about whether there was pre-columbian contact between the Polynesians – from mid-Pacific islands like Hawaii, Tahiti, and Easter Island –  and natives of the Americas, that is to say, before the New World was “discovered” by the Europeans. In fact, at one time it was even considered possible that the Polynesians originated in Central or South America and set out from the New World to conquer the various islands.

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Travels of the Polynesians.

Today genetic studies of human populations in Polynesia prove beyond doubt that they arrived at their remote islands in successive waves from the island of Taiwan and that there is no trace of them in the genetics of the Amerindian peoples… but this does not exclude the possibility that the Polynesians could have crossed the 4000 km between Polynesia and South America without leaving any descendants.

For that reason, scientists have been looking for other proofs of contact between the two peoples, such as plants and animals they may have transported between the two territories.

False Leads

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Coconuts do float from island to island and remain viable: but could they travel across the Pacific ocean?

For some time, it was believed that the presence of coconut palms (Cocos nucifera) on the West Cosat of Central America, apparently predating any possible European exchanges, was evidence of these Polynesian/Amerindian exchanges. After all, it is known that the Polynesians transported the species from the Indian Ocean throughout Polynesia. And early Spanish explorers reported the presence of coconut palms at Cocos Island off Costa Rica and a few other spots along the west coast of South and Central America. For the moment, though, it remains insufficiently clear that the palms they saw were actually coconut palms and not some other species. For example, there are no coconut palms on Cocos Island today nor any proof they were ever found on the island. And there remains the remote possibility that coconuts could have floated there on their own. So, for the moment, the coconut theory has to be put to one side.

Very recently, another theory on this subject came up (in 2007) and was quickly refuted (2014); one that claimed Polynesians introduced chickens to South America. But the 2014 study showed that the genetics of old chicken bones from western South America and from Polynesia are not the same. Instead, the New World birds bear traits of European poultry. Read Chicken DNA Challenges Theory That Polynesians Beat Europeans to Americas for more information.

The Travelling Tuber

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Sweet potatoes.

Nowadays the sweet potato (Ipomoea batatas) is cultivated throughout the world, but it originated in South and Central America. That’s where it has been cultivated for the longest time (at least 5,000 years, perhaps even 8,000 years) and also where we find its wild ancestors. (The sweet potato is a cultigen – a plant created by humans through repeated selections from one or more wild species – and that does not exist in the wild.)

The sweet potato is therefore clearly not native to the Polynesian islands and yet, when Captain James Cook visited them during his various voyages between 1768 and 1779, the natives were already growing them. In fact, he collected specimens of sweet potatoes that are kept in European herbaria.

The question then becomes: how did the South American sweet potato cross a third of the Pacific (at least 4000 km!) before European sailing vessels got there if not through contact with the Polynesians?

Different Theories

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Sweet potato tubers don’t travel well.

Some specialists at first argued that sweet potato seeds or tubers could have crossed the ocean by floating there. After all, it is known that certain plants did spread from the New World to Polynesia that way. But only seeds able to float for long months while remaining viable were able to make this transit. Tests have revealed, not surprisingly (possibly a wild plant might have made the trip, but a cultivated one?), that neither sweet potato tubers nor seeds have that ability.

Others believed that the sweet potato could have been transported and distributed in Asia by the Spaniards and Portuguese in the 16th century (after the discovery of the New World) and that it would have gradually reached the Pacific Islands via inter-island exchanges. In other words, according to this theory, what Cook had discovered was a recently introduced plant.

But modern studies show that to be impossible. DNA analysis of the specimens harvested by Cook indicate that they are of the kumara lineage, originating in western South America, not either of the lineages the Europeans spread throughout Africa and Asia, lineages originating in western Mexico (the camote lineage) and the Caribbean Islands (the batata lineage).

In addition, sweet potato remains were found in the Polynesian Islands (Hawaii, New Zealand, the Cook Islands) that predate the European discovery of the New World. The Cook Island specimens have been dated to about the year 1000 and many researchers believe the sweet potato reached the Polynesian islands even earlier, around 700 AD or even 300 AD. So the sweet potato was already present in the Pacific islands at least 700 years before the visit of James Cook and at least 550 years before Europeans brought certain lineages of sweet potato to Asia. Moreover, it has now been proved that the sweet potato lineage the ancient Polynesians grew comes from the western coast of South America (Ecuador, Peru, etc.) and not elsewhere in the New World and is a lineage the Spanish and Portuguese never distributed.

Pre-Columbian Contacts

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Ornamental sweet potatoes are popular in gardens worldwide.

It would appear that the only conclusion to be drawn is that the sweet potato was transported to the Polynesian islands long before the Europeans discovered the New World. But how?

The general consensus today is that the Polynesians, already famous for their ability to cross vast expanses of ocean in their outrigger canoes (which is how they came to inhabit the Polynesian islands to start with!) must have visited the west coast of South America and from there brought the sweet potato back to their islands.

Of course, the opposite is also possible, that the South American peoples were greater navigators than is currently thought and that they left their continent with tubers on board their boats, eventually reaching the islands of Polynesia. Most experts consider this theory to be most unlikely, though. The “Polynesians discovered the New World” theory is by far the most widely accepted one.

Whatever the direction, however, the consensus today is that there were indeed exchanges between America and Polynesia long before the arrival of the Europeans… and it is the sweet potato that is the best proof.

A Shared Name

One final intriguing detail: the name of the sweet potato in the Quecha language of the inhabitants of the Pacific coast of South America is kumara and while it is kuumala in the Polynesian islands. That is perhaps another indication of this distant contact… or maybe it’s just a coincidence!

The next time you eat or plant sweet potatoes, it may be worth remembering their fascinating history and what they tell us about our planet’s prehistory.20161128a

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