I just read this.
Sweet potato was taken from its American homeland by Polynesians who introduced it into many Pacifc islands and New Zealand about 1000 years ago.
The only thing I previously read about Polynesians traveling from South America to the Islands was rejection of the Kon-Tiki hypothesis.
What else is known?
Where did you read it? A cite-less quote is neither persuasive nor informative.
I found a number of references to the hypothesis on Wikipedia, including this, on the “Sweet potato cultivation in Polynesia” page:
There is also an entire article on Wikipedia about “Pre-Columbian transoceanic contact theories,” with a section on possible Polynesian contact. Lots of hypotheses and theories, including using the presence of the sweet potato as evidence, but no definitive evidence, IMO.
IIRC, his hypothesis was mainly that they could have sailed from South America, which he did prove.
His aim in mounting the Kon-Tiki expedition was to show, by using only the materials and technologies available to those people at the time, that there were no technical reasons to prevent them from having done so.
However, we now know the Polynesians came from the East. At least mostly-
Recent genetic studies have also suggested that some eastern Polynesian populations have admixture from coastal western South American peoples, with an estimated date of contact around 1200 CE.[5]
That doesnt mean the Polynesians couldnt have sailed on to South America or Easter island and nabbed some plants. However, certainly there is no evidence of repeated trading missions or anything like that.
Polynesians had the technology and skills necessary to travel to and from the Americas 1,000 years ago. I doubt native Americans had the maritime tech to even go one way.
Also, it’s a lot easier to go from Polynesia to the Americas than the reverse, from a navigation standpoint. Pick any point anywhere in the Pacific, and go anywhere generally vaguely eastward, and you’ll hit land eventually. The other direction, though, your targets are small islands. The Polynesians themselves knew how to find those islands (there are subtle clues in the waves that an island is nearby but below the horizon, and you can look for shore birds), but others might not.
It’s interesting that the genetic admixture is from South America to Polynesia. Is there any in the other direction? It’s easier for the adventuring population to spread their genes: A seafarer (who was probably a man) travels to some far-away land, and gets a local woman pregnant before leaving. To get gene flow the other way, though, you have to either have seafaring women (who get pregnant in the distant land before coming back), or you have to transport back live people, which is logistically more difficult.
Maybe it’s because of the disparity in population sizes? A dozen pregnancies will have a much bigger impact on a small Polynesian island than ten times as many will have on the Andean civilization.