The origin and domestication of sweet potato is thought to be in
either Central America or South America. In Central America, sweet
potatoes were domesticated at least 5,000 years ago. In South
America, Peruvian sweet potato remnants dating as far back as 8000
BC have been found.
One author postulated that the origin of I. batatas was between the
Yucatán Peninsula of Mexico and the mouth of the Orinoco River in
Venezuela. The cultigen had most likely been spread by local people
to the Caribbean and South America by 2500 BC. Strong supporting
evidence was provided that the geographical zone postulated by
Austin is the primary center of diversity. The much lower molecular
diversity found in Peru-Ecuador suggests this region should be
considered as a secondary center of sweet potato diversity.
The sweet potato was grown in Polynesia before western exploration.
Sweet potato has been radiocarbon-dated in the Cook Islands to 1000
AD, and current thinking is that it was brought to central
Polynesia around 700 AD, possibly by Polynesians who had traveled
to South America and back, and spread across Polynesia to Hawaii
and New Zealand from there. It is possible, however, that South
Americans brought it to the Pacific, although this is unlikely as
it was the Polynesians, and not the native South Americans, who had
a strong maritime tradition. The theory that the plant could spread
by floating seeds across the ocean is not supported by evidence.
Another point is that the sweet potato in Polynesia is the
cultivated Ipomoea batatas, which is generally spread by vine
cuttings and not by seeds.