Relying in part on Heyerdahl's conclusions, scientists have long believed the island was colonized around A.D. 400. More recently, researchers argued that settlement first took place around the year 800.
The deforestation of Easter Island is believed to have begun around 1300, suggesting that there was a period of several centuries during which the islanders lived in harmony with the environment.
Fuel for the Fire
The new study by Hunt and his colleague Carl Lipo, however, suggests that the Polynesians didn't arrive until around 1200. The deforestation began soon thereafter, they say.
The scientists took eight samples of wood charcoal from the bottom of the oldest known archaeological site on the island, Anakena. Radiocarbon dating placed them at around the year 1200.
"This is the first sign of human activity at Anakena and probably for the island," Hunt said. "There is no longer any evidence for settlement earlier than about 1200 A.D."
The findings suggest the island did not enjoy the kind of Garden of Eden period for 400 to 800 years that researchers had previously imagined.
Instead the Polynesians immediately began destroying the trees and giant palms, using the wood for their canoes, for fires, and perhaps for moving statues.
"Radiocarbon dates show that deforestation took place over 400 to 500 years," starting around 1200, Hunt said.
"This is consistent with our shorter chronology and the observations made by the Dutch in 1722."
Most of the island animals, particularly birds, lost their habitat and were wiped out. Native animals also suffered direct predation from the Polynesian rat, which the colonizers brought with them to the island.
"Like problems of invasive species today, [the rat] probably had a widespread and devastating impact on the island's ecologyparticularly the palm trees and also directly or indirectly on birds," Hunt said.
"Rats would grow to huge numbers and consume the seeds of trees, and regeneration of the forest would essentially stop."
The new results appear to back up other recent studies that suggest later dates for colonization of islands in the region.
For example, it is now thought that New Zealand was colonized after 1200, about 400 years later than has long been assumed.
To understand the functioning of island ecosystems, it is important to sort out natural processes from human impacts. This requires dependable time lines of human habitation.
"This need for reliable chronologies is especially magnified for Pacific islands, because in so many cases the advent of human settlement has led to massive alteration of the natural landscapes," said Stephen Athens, general manager of the nonprofit International Archaeological Research Institute, Inc., in Honolulu.
Athens, who was not involved with the new study, says a relatively late settlement of Easter Island is to be expected, given the revised chronologies of its neighbors in eastern Polynesia.
"One of the most significant conclusions we can draw from studies [like these] is just how extremely sensitive the natural ecosystems of many islands are to the advent of humans, with the degree of sensitivity apparently related to isolation and endemism of the fauna and flora," Athens said. "Endemism" refers to species that are found naturally in only one location.
In the case of Easter Island, Athens said, "we are indeed seeing humans initiating ramifying processes over which they lose control."
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