The long-standing argument over the eventual fate of native Polynesians who once lived on Easter Island may be over, new research suggests.

Many scientists have argued that the Rapa Nui people of the isolated island in the southeaster Pacific Ocean died out because they exhausted the natural resources available to them on the small island of just 63 square miles.

Others have claimed it was disease and pestilence brought to the island by Europeans in the early 18th century that decimated the native population, with many of the survivors then taken as slaves.

However, it may have been preexisting environmental conditions, rather than internal or external human influences, which set the stage for the downfall of the Rapa Nui, the authors of a new study suggest.

They may have been victims of environmental changes that took a toll on the island's population over centuries, rather than a rapid, large-scale collapse from either resource depletion or introduced diseases, they suggest.

"The results of our research were really quite surprising to me," says study co-author Thegn Ladefoged, an anthropologist with the University of Auckland in New Zealand. "Indeed, in the past, we've published articles about how there was little evidence for pre-European-contact societal collapse."

However, an analyses of obsidian weapons and tools from various sites on the island showed shifting human uses of different parts of Easter Island and its natural resources, which suggests varying degrees of success of failure in attempts to adapt to changing environmental conditions, the researchers report in the Proceedings of the National Academy of Sciences.

Variations in climate around the island may have led to inexorable but uneven declines in population, they explain.

One site studied sits in the rain shadow of a volcano and would have been prone to drought; another site would have been wetter but shows low soil fertility.

A third site, believed to be where the Rapa Nui held out for longest, was both rainy and fertile, the researchers say.

The findings suggest natural environmental barriers, and the extremes of climate, might have been negatively impacting the island's inhabitants, rather than a decline caused by them degrading the environment by using up all available natural resources, they say.

And their decline almost certainly was well underway before the arrival of Europeans, they add.

"It is clear that people were reacting to regional environmental variation on the island before they were devastated by the introduction of European diseases and other historic processes," Ladefoged says.

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