Clues to Prehistoric Human Exploration Found in Sweet Potato Genome
Lizzie Wade, Science, 21 January 2013 (hat tip: NC)
Humans domesticated the sweet potato in the Peruvian highlands about 8000 years ago, and previous generations of scholars believed that Spanish and Portuguese explorers introduced the crop to Southeast Asia and the Pacific beginning in the 16th century. But in recent years, archaeologists and linguists have accumulated evidence supporting another hypothesis: Premodern Polynesian sailors navigated their sophisticated ships all the way to the west coast of South America and brought the sweet potato back home with them. The oldest carbonized sample of the crop found by archaeologists in the Pacific dates to about 1000 C.E.—nearly 500 years before Columbus's first voyage. What's more, the word for "sweet potato" in many Polynesian languages closely resembles the Quechua word for the plant.
Because the Polynesians, like Vikings on the opposite end of the new world, didn't take over and conquer the new people, the remnants of their transitory visits is rather ephemeral. Just as with the Norwegians, now that their arrival is established it will be easier to pinpoint further examples without being labelled a crackpot.
Likely, as with other large cultural groupings, the extent of their reach waxed and wained over time.