Rethinking the Fall of Easter Island
New evidence points to an alternative explanation for a civilization's collapse
A Misplaced Metaphor?
By the time the second round of radiocarbon results arrived in the fall of 2005, a complete picture of Rapa Nui's prehistory was falling into place. The first settlers arrived from other Polynesian islands around 1200 A.D. Their numbers grew quickly, perhaps at about three percent annually, which would be similar to the rapid growth shown to have taken place elsewhere in the Pacific. On Pitcairn Island, for example, the population increased by about 3.4 percent per year following the appearance of the Bounty mutineers in 1790. For Rapa Nui, three percent annual growth would mean that a colonizing population of 50 would have grown to more than a thousand in about a century. The rat population would have exploded even more quickly, and the combination of humans cutting down trees and rats eating the seeds would have led to rapid deforestation. Thus, in my view, there was no extended period during which the human population lived in some sort of idyllic balance with the fragile environment.
It also appears that the islanders began building moai and ahu soon after reaching the island. The human population probably reached a maximum of about 3,000, perhaps a bit higher, around 1350 A.D. and remained fairly stable until the arrival of Europeans. The environmental limitations of Rapa Nui would have kept the population from growing much larger. By the time Roggeveen arrived in 1722, most of the island's trees were gone, but deforestation did not trigger societal collapse, as Diamond and others have argued.
There is no reliable evidence that the island's population ever grew as large as 15,000 or more, and the actual downfall of the Rapanui resulted not from internal strife but from contact with Europeans. When Roggeveen landed on Rapa Nui's shores in 1722, a few days after Easter (hence the island's name), he took more than 100 of his men with him, and all were armed with muskets, pistols and cutlasses. Before he had advanced very far, Roggeveen heard shots from the rear of the party. He turned to find 10 or 12 islanders dead and a number of others wounded. His sailors claimed that some of the Rapanui had made threatening gestures. Whatever the provocation, the result did not bode well for the island's inhabitants.
Newly introduced diseases, conflict with European invaders and enslavement followed over the next century and a half, and these were the chief causes of the collapse. In the early 1860s, more than a thousand Rapanui were taken from the island as slaves, and by the late 1870s the number of native islanders numbered only around 100. In 1888, the island was annexed by Chile. It remains part of that country today.
In the 1930s, French ethnographer Alfred Metraux visited the island. He later described the demise of Rapa Nui as "one of the most hideous atrocities committed by white men in the South Seas." It was genocide, not ecocide, that caused the demise of the Rapanui. An ecological catastrophe did occur on Rapa Nui, but it was the result of a number of factors, not just human short-sightedness.
I believe that the world faces today an unprecedented global environmental crisis, and I see the usefulness of historical examples of the pitfalls of environmental destruction. So it was with some unease that I concluded that Rapa Nui does not provide such a model. But as a scientist I cannot ignore the problems with the accepted narrative of the island's prehistory. Mistakes or exaggerations in arguments for protecting the environment only lead to oversimplified answers and hurt the cause of environmentalism. We will end up wondering why our simple answers were not enough to make a difference in confronting today's problems.
Ecosystems are complex, and there is an urgent need to understand them better. Certainly the role of rats on Rapa Nui shows the potentially devastating, and often unexpected, impact of invasive species. I hope that we will continue to explore what happened on Rapa Nui, and to learn whatever other lessons this remote outpost has to teach us.
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