One of the enduring mysteries of world history is whether the Americas
had any contact with the Old World before Columbus, apart from the
brief Viking settlement in Newfoundland. Many aspects of higher
civilisation in the New World, from the invention of pottery to the
building of pyramids, have been ascribed to European, Asian or African
voyagers, but none has stood up to scrutiny.
The one convincing piece of evidence for pre-Hispanic contact has been
the humble sweet potato, which is of tropical American origin but
widely cultivated across the Pacific islands. Until a few years ago it
was assumed that this was the result of Spanish transmission, dating
to the early colonial period, but archaeological discoveries in the
Cook Islands show this to be wrong: excavations at Mangaia yielded
carbonised remains of sweet potato (Ipomoea batatas) dating to AD1000,
five centuries before Europeans entered the Pacific Ocean.
The question then arose as to whether the diffusion of this useful
crop was the result of Amerindians sailing west to Polynesia, as the
late Thor Heyerdahl always claimed, or whether it came about because
Polynesians exploring on “the road of the winds” beyond Easter Island
came to the South American mainland, and took back with them the hardy
and nutritious root crop which is today fifth in importance in
developing countries.
The lack of evidence for Native American seafaring and the reputation
of the Polynesians as navigators inclined most scholars to the latter
thesis: but a new simulation study suggests that either the
Amerindians or nature may have been responsible: Alvaro Montenegro and
his colleagues in the Journal of Archaeological Science argue that
computer experiments demonstrate that accidental drift voyages could
have been responsible.
The experiment was set up to investigate two transfer theories, by
accidental voyages from the American mainland that reached Polynesia,
and drifting of Ipomoea seed capsules. Deliberate voyaging was not
included.
Starting positions were in a series of “departure bins” defined off
the Central and South American coastlines from 50 degrees south to 30
degrees north — roughly from southern Chile to northern Mexico.
The drifter point was located at the centre of each bin, and thus some
distance offshore. The various Pacific island groups were designated
as targets, and the probable drift of vessels the size of a large
canoe under the influence of the known winds and currents simulated
over a six-month period; the drift of seed capsules was simulated for
a full year.
The most probable canoe crossing to score a “hit” was from Central
America to the Marshall Islands, with a likelihood of 11.5 per cent.
The much shorter crossing from Ecuador to the Gal�pagos was second, at
almost 10 per cent, followed by the central Polynesian island groups
of Tuamotu and the Marquesas at 7.4 and 5.7 per cent repectively. Most
other targets scored very low, although Hawaii had an almost 3 per
cent chance of being encountered.
The drifting seed capsules had a 17.4 per cent chance of reaching the
Gal�pagos, only 600 miles off Ecuador, with the Marquesas at 2.7 per
cent the next most likely hit. Hawaii cultivated the crop before
European contact, and probably got it from Mexico on the basis of the
simulation, but there was no further onward dispersal. This route
might well have been used in the putative Polynesian-Californian
contacts recently proposed (The Times, November 21, 2005).
The fact that 16 of the 23 target areas were hit with at least 1 per
cent probability indicates “that vessel drifts provide many access
routes from South America into Polynesia”, with hits on a particular
island group coming from drifters starting on specific stretches of
American coastline. These could have informed Polynesians of lands to
the east, making two-way traffic possible.
The lowly sweet potato may unlock America's past, How the root vegetable found it's way across the Pacific
The date by which all this happened remains debatable. Expansion east
out of Tonga and Samoa may have begun as early as AD1, but perhaps not
much earlier than AD1000, when the sweet potato is attested in the
Cook Islands.
Easter Island seems, on the latest evidence, not to have been settled
until around AD1200, so it could not have played a part in the initial
transmission. In the end what this simulation experiment tells us is
that purposeful voyaging, in either direction, was not necessary for
this first, tenuous contact between the settlers who had moved out of
Asia and around the Pacific rim to settle first the continent of
America and then, much later, the ocean wastes of the Pacific.
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