In shards of glass, a new sign of how the enigmatic Easter Islanders met their demise

Moai, or Easter Island's enigmatic statues, at the Rano Raraku quarry on Easter Island in 2013. Photo / Chaney Kwak, The Washington Post

For years, the glimmering glass blades found scattered across the island were seen as evidence of its former residents' bloodshed. Their environment denuded and their livelihoods compromised by deforestation and overuse of the land, the people of Easter Island were driven to warfare, scholars said, and the once-thriving society that built the massive moai monoliths dwindled down to just a few hungry hundreds.

"It represents such a classic case of people potentially using up resources and ending up in fighting and warfare," Carl Lipo, an archaeologist at Binghamton University, in New York, told the BBC World Service.

So classic that researchers like Jared Diamond (of "Guns, Germs and Steel" fame) held the island up as a cautionary tale for modern readers: "the clearest example of a society that destroyed itself by overexploiting its own resources."

As the story goes, these descendants of a small group of intrepid Polynesian settlers who landed on the island somewhere between AD 700 and 1200 after canoeing more than 1,000 miles across the open Pacific were once a flourishing community of farmers. They built hundreds of moai statues, tremendous, hollow-eyed and imposing, that are still considered an engineering marvel. But their rapid growth and rapacious slash-and-burn agriculture devastated the landscape, Diamond and others argue.

Easter Island statues (moai) at Ahu Akivi, Easter Island. Photo / Supplied

The ecosystem collapsed, bringing the Easter Island society down with it. Clans went to war over the scant remaining food sources, and in some cases even resorted to cannibalism. The people whose whose engineering prowess was such that their ability to build and move their massive statues still defies historians' best explanations, were all but vanished. It was a sad case of what Diamond calls "ecocide."

"If mere thousands of Easter Islanders with just stone tools and their own muscle sufficed to destroy their environment and thereby destroyed their society," he wrote in his 2005 book "Collapse: How Societies Choose to Fail or Succeed, "how can billions of people with metal tools and machine power now fail to do worse?"

It is a chilling narrative, but it may not be accurate, Lipo said. He's the lead author of a new study in the archaeological journal Antiquity arguing that the ubiquitous mata'a blades often referenced in accounts of the island's collapse are not weapons after all - they're just tools. And they're further proof, Lipo says, that we're telling the wrong story about what happened on Easter Island. It's not a morality tale about the perils of excess - it's a saga about an inventive people who engineered their environment to make the most of scant resources, only to fall prey to disease and human avarice once European explorers arrived.

This is an argument that Lipo and his co-author, Terry Hunt, have been making for a while - almost since they began studying Easter Island, also called Rapa Nui, in 2000. In their book, "The Statues that Walked," they say that stowaway rats that accompanied the original Polynesian settlers to the island were largely responsible for the rapid deforestation that happened there. But rather than collapse into desperation and discord, the residents of Easter Island found ways to cope.

Easter Island statues (moai) at sunset at Tahai. Photo / Supplied

No longer able to fish, since they lacked the lumber to build canoes, the islanders established a diet based on rat meat. Their soil degraded by the rapid ecological change, they burned trees and planted gardens of broken rock to enrich it; when the sea winds tumbled over the bits of stone, extra nutrients were released into the soil, boosting its productivity enough to sustain subsistence-level agriculture. Society on the island was diminished, perhaps, but it was not destroyed.

The mata'a blades are the latest piece of evidence that Lipo and Hunt are presenting for their theory. These triangular slices of obsidian - a glittering-black volcanic rock - were originally thought to be spear points, according to a Binghamton University press release.

But when Lipo, Hunt and their colleagues conducted a quantitative analysis of more than 400 of the blades, they found that the pieces of glass would have made very poor weapons and bore little resemblance to other types of spears from similar civilisations.

"European weapons or weapons found anywhere around the world when there are actually objects used for warfare . . . [are] very systematic in their shape. They have to do their job really well. Not doing well is risking death," Lipo said in the release.

The mata'a, by contrast, varied widely in shape and size and weren't engineered for fighting. Rather than being long and thin, fit for piercing bodies and slicing open organs, they were short and wide - more like a spade than a spear, he told the BBC.

Rapa Nui giant stone sculptures. Photo / Angela Gregory

"There's just no evidence to support that these were used in a systematic lethal fashion," Lipo said. "They were wildly different than that and had really distributed kind of shapes that would be very poor weapons."

This seems to support the idea that the island didn't go through a period of infighting and ruin, he argues. In a society where warfare is rampant and violence may be the only means of survival, people surely would have learned to make better weapons than the ones that Lipo and Hunt found. It's more likely that the blades were used for ritual and cultivation purposes - tattooing, plant processing and so on - and were rarely turned on a fellow human.

So, if it wasn't internal conflict that killed the island's inhabitants, what is responsible?

"Disease that was introduced and slavery that brought people off the island," Lipo told the BBC.

The first recorded evidence of European contact with the island's people comes from 1722, when Dutch explorer Jacob Roggeveen visited the island for a week. He wrote that the population was somewhere in the thousands - a number that was likely an underestimate, since many inhabitants went into hiding after Roggeveen and his men shot and killed about a dozen of them. The interaction did not bode well for the people of the island, which Roggeveen himself described as "exceedingly fruitful" when he visited.

But a century and a half later, after years of conflict, disease and slave raids by Europeans had taken their toll. Just 111 inhabitants remained on the island by the 1870s.

This theory has critics. Diamond wrote a rebuttal to Lipo and Hunt's book in 2011, arguing that the researchers overestimated the effect of rats, cite a too-late-date for initial Polynesian settlement of the island and ignored evidence of slash-and-burn's destructive impact. In a letter to Current World Archaeology magazine, the Easter Island experts Paul Bahn and John Flenley also took issue with Lipo and Hunt's claims. They point out that analysis of prehistoric skeletons showed evidence of lethal trauma, and there is a long oral tradition on the island of stories about a violent past.

But there's also a growing group of researchers who support the unorthodox claim. Mara Mulrooney, a Hawaiian anthropologist, published a study in 2013 arguing that nutrient levels in the soil across the island actually improved with deforestation. Rather than bringing about their ruin, the removal of their island's trees was a strategy to help the island's inhabitants survive.

"They made the environment more productive from a food point of view," Mulrooney told NPR.

The reason archaeologists had fixated on the "ecocide" argument for so long, she added, is that it fit with existing narratives about Easter Island that went all the way back to the 1700s.

"Archaeologists, instead of looking at the evidence itself, were taking the evidence and putting it into this existing framework that was really outdated," she said.

Christopher M. Stevenson of Virginia Commonwealth University complicated the issue with a paper published in the Proceedings of the National Academy of Sciences last year. In it, he said that the island saw demographic changes prior to European contact, but they were shifts cased by altered weather patterns, not a starvation-induced crash. The rapid collapse came later, after European explorers brought smallpox, syphillis and slavery to the island.

Perhaps there is no one story about Easter Island, no narrative that fits neatly over one of the world's most isolated and enigmatic places. And that's okay, Mulrooney told NPR. That's how science is supposed to work.

"Perhaps the story may change, perhaps the pendulum may swing back toward supporting a collapse," she said. "But as of now, you know, I like to think that as scientists we trust what the data tell us."

"That's the beauty of archaeology, is that it's always changing."