In the popular imagination, the history of Easter Island has long been centered on stone. About 900 monolithic statues, or âmoai,â have been identified on Easter Island, a 63-square-mile distant triangle in the Pacific Ocean whose native name is Rapa Nui. The statues – haunting faces with sunken eyes – were made from massive blocks of volcanic rock by the Rapa Nui people, who settled on the island around 1200 CE.
But for archaeologists and anthropologists, Rapa Nui’s story has often centered around trees, rats, and the climate. These are the key factors, according to some researchers, which led to an ecological disaster on the island and, as a result, the collapse of the population.
A popular account argues that Rapa Nui’s growing population has cut down so many of the island’s tall palm trees that they have depleted their food and logistical resources and inadvertently killed plant and animal species. Meanwhile, Polynesian rats, which were transported to the island by boat and have multiplied exponentially over generations, have contributed to deforestation by eating seeds and plants. The island’s problems were compounded by changes in the El NiÃ±o Southern Oscillation, which led to drier conditions.
Faced with dire circumstances, the natives probably resorted to eating rats. They might have started eating each other too, suggested author Jared Diamond in his book. Collapse, in which he declares that Rapa Nui is “the clearest example of a society that destroyed itself by over-exploiting its own resources”.
Breaking the myth of the Easter Island collapse
But the popular account on Easter Island could be largely wrong. New research suggests that these accounts linking environmental devastation to population decline are not accurate. The study, published in Nature Communication, found that while the Rapa Nui people underwent environmental and climatic changes, they did not suddenly decrease in numbers but rather maintained “stable and sustainable communities on the island” until the moment they encountered the Europeans.
To estimate population changes over time, the researchers tested four demographic models, three of which took into account variables such as climate change or deforestation or both. Their models also incorporated around 200 radiocarbon dated archaeological samples, which provide a good âproxy for estimating the relative size of populationsâ.
moai statueskovgabor79 via Adobe Stock
Radiocarbon dating and statistical modeling always involve uncertainties. To minimize analytical uncertainty, the researchers used a form of statistical modeling called approximate Bayesian calculus. The researchers wrote:
“[Approximate Bayesian Computation] is a flexible and powerful modeling approach originally developed in population genetics, but recently applied in archeology, including paleodemographic research. We demonstrate how ABC can be used to directly integrate independent paleoenvironmental variables into demographic models and perform multi-model comparisons.
Results produced by the four models showed that Rapa Nui’s population grew steadily until first contact with Europeans in 1722, after which the population appeared to level off or decline over the following decades. These models suggest that, unlike previous assumptions about how overexploitation of resources led to population collapse, deforestation and climate change on the island were protracted processes that did not have catastrophic effects on the island. population.
For example, evidence suggests that the Rapa Nui people built productive gardens on deforested land and covered them with nutrient-rich stone. As for climate change, the researchers pointed to recent studies suggesting that natives have adapted to drier conditions by turning to coastal groundwater sources.
Reversing a long-standing narrative
Although the study offers evidence of a robust population prior to European contact, the researchers could not determine which of the four demographic models was the most correct, nor did they take into account other factors that may affect the population of the island, like the war. The researchers also did not explore what effect, if any, the European contact had on the population.
But overall, the study casts serious doubts on the popular narrative that environmental changes have driven down the indigenous population. Granted, there are dark chapters in Rapa Nui’s history, including the civil war, slave raids, and the destruction of statues; reports suggest that between 1722 and 1774 many statues on the island were toppled or neglected, possibly due to internal conflicts between the natives.
Yet the study suggests that the story of the early Rapa Nui is less about environmental destruction than resilience.
The researchers conclude that âdespite extreme isolation, marginal ecological conditions and a series of environmental changes, the people of Rapa Nui found solutions that allowed them to thrive successfully on the island for at least 500 years before the arrival of Europeans â.