Evidence for precolumbian connections between Polynesia and South America are trickling in these days; but what kind of connection and what is the evidence?
Back in the mid-20th century, the idea that pre-Columbian voyages across the Pacific took place was promulgated by a small group of scientists and enthusiasts. Best known was the Norwegian adventurer Thor Heyerdahl, who built the raft KonTiki and sailed it across the Pacific in 1947, proving that it was possible. On the scientific side, American archaeologist Betty Meggers looked at the ceramic pots recovered from the 2500 BC site of Valdivia and saw body form and ceramic decoration similarities to the Middle Jomon period of Japan.
But neither of these ideas really made it into the mainstream, partly because, at least in Heyerdahl's case, they were couched in terms of population origins--that is to say, they were part of a discussion about whether the Polynesians originated from the Americas or vice versa. Further, crossing the Pacific with limited technology is not an easy journey by a long shot, as Heyerdahl showed; and for substantial cultural contact you need lots of people--basically, a colonization force that is not warranted by any substantial data anywhere to day.
While the ideas of massive colonization of either side of the Pacific have faded, the notion of contact of some sort between the South American coast and Polynesia is beginning to take on serious scholarship. Two recent areas of research have produced information concerning the trans-pacific crossings: sweet potatoes and chickens.
Sweet Potatoes and Trans-Pacific Voyages
Sweet potatoes (Ipomomea batatas) are a New World domesticate root crop, that originated in northern South America or Central America about 2500 years ago. Most of the world uses this very tasty and nutritious crop, and most of the world got the sweet potato due to the efforts of the Spanish and Portuguese explorers who found the sweet potato in Peru and Mexico and exported it to Europe and Africa. However, there is secure evidence that several of the Polynesian islands got the sweet potato long before Columbus and Magellan set sail.
In a 2008 article called Modeling the prehistoric arrival of the sweet potato in Polynesia, Alvaro Montenegro, Chris Avis, and Andrew Weaver describe a series of computer simulations of accidental drift voyages from different points in the Americas. Basically, researchers used ECCO data of hypothetical wind and tide currents for the Pacific and then hypothesized rafts setting off from the Pacific coastlines of North and South America. Their hypothetical movements were recorded, and, if a drifting vessel hit one of the target areas within 180 days--target areas being various islands or island groups in the Pacific--then the trip was recorded as successful.
And, of the 23 targets established in the Pacific, indeed 19 were hit, 16% with at least 1% probability, and eight with 2% or better. The most probable (11.45%) was from Central American and Mexico to the Marshall Islands. An interesting paper, and well worth a look.
Polynesian Chickens in Chile
Chickens, on the other hand, likely originated in southeast Asia, although Northern and Southern China, India, Burma and Thailand have all been proposed. The latest scoop on chickens is that they were domesticated from the red junglefowl, probably in Thailand, and probably about 8,000 years ago. They are believed to have reached the Polynesian islands about 3,000 years ago, brought by the Lapita expansion.
A 2007 paper written by Alice Storey and colleagues reported on excavations at the site of El Arenal-1. El Arenal-1 is located in south central Chile, and is part of the El Vergel Cultural Complex of horticulturalists, dated between AD 1000 and 1500. Fifty chicken bones were recovered from the site, representing a minimum of five birds. The bones themselves were radiocarbon dated, and returned a calibrated age range of AD 1304-1424. DNA studies associated with the study indicated that these chickens were genetically similar to chicken bones from two prehistoric sites in the Pacific: Mele Havea in Tonga (2000-1550 years old), and Fatu-ma-Futi in American Samoa, which dates to about the same period as El Arenal.
In 2008, a paper in PNAS by Gongora et al. contradicted the findings of Storey et al. Read about it here: Chickens and Trans-Pacific Crossings, Part 2. And In 2014, examination of mtDNA from 13 ancient and modern chickens, and comparison to 46 other published DNA sequences led Thomson et al. to argue that the haplogroup indicating the founding lineage for Polynesian chickens was not E, as argued by Storey et al., but Haplogroup D, a DNA group associated with cockfighting. See a detailed discussion in the "Chickens in America, Revisited" section of the Domestication of the Chicken page.
Coconuts and Bottle Gourds
New (and not so new) evidence supporting these trans-pacific crossings has been examined concerning the presence of both coconuts and bottle gourds. DNA studies of coconuts (Cocos nucifera) growing today in Ecuador and reported by the Spanish conquistadors indicates that they originated in the Philippines, and were brought to Ecuador by seafarers ~2250 years BP (Baudouin and Lebrun 2009).
The earliest bottle gourds (Lagenaria siceraria) have been discovered in southwest Ecuador dated to 9300 BP and they are believed to have originated there. The bottle gourd appears in Polynesia by ca. AD 1000. Recent DNA investigations (Kistler et al.) suggest, however, that the bottle gourd arrived on the eastern coast of central America by floating over from Africa, and was domesticated there. See a discussion on the main bottle gourd page.
It would seem that there is solid evidence for precolumbian connections between Polynesia and the Americas by approximately AD 1300, and perhaps earlier still. What kind of connection seems at presently likely to be accidental and fleeting, and at this point it is wise to remain cautious--but developments such as these should be watched for in the months and years to come.