Now we have even more evidence against the theory of “ecocide” on Easter Island

Enlarge / New research lends more credence to the “demographic decline” theory that Easter Island is just a myth.

Arian Zwegers/CC POR 2.0

For centuries, Western scholars have touted the fate of the native population of Easter Island (Rapa Nui) as a case study of the devastating cost of environmentally unsustainable living. The story goes that the people of the remote island cut down all the trees to build huge stone statues, causing a demographic collapse. Their numbers were further reduced when Europeans discovered the island and brought foreign diseases, among other factors. But in the 21st century an alternative narrative began to emerge that the early inhabitants were actually living quite sustainably up to that point. A new paper published in the journal Science Advances offers another key piece of evidence supporting that alternative hypothesis.

As previously reported, Easter Island is famous for its giant monumental statues, called moaibuilt about 800 years ago and typically mounted on platforms called ahu. Scholars have asked about the moai on Easter Island for decades, reflecting on its cultural importance, as well as how a Stone Age culture managed to carve and transport statues weighing up to 92 tons. The first Europeans arrived in the 17th century and found only a few thousand inhabitants on a small island (just 14 by 7 miles wide) thousands of miles away from any other land. Since then, to explain the presence of so many moaiIt has been assumed that the island was once home to tens of thousands of people.

But maybe they didn’t need tens of thousands of people to accomplish that feat. In 2012, Carl Lipo of Binghamton University and Terry Hunt of the University of Arizona demonstrated that a 10-foot, 5-ton vehicle could be transported. moai a few hundred meters with only 18 people and three strong ropes using a swinging motion. In 2018, Lipo proposed an intriguing hypothesis about how islanders placed red hats on top of some moai; These can weigh up to 13 tons. He suggested that residents use ropes to roll hats down a ramp. Lipo and his team later concluded (based on quantitative spatial modeling) that the islanders likely chose the statues’ locations based on the availability of freshwater sources, according to a 2019 paper in PLOS One.

In 2020, Lipo and his team turned their attention to establishing a better chronology of human occupation of Rapa Nui. While it is generally accepted that people arrived in Eastern Polynesia and Rapa Nui sometime in the late 12th century or early 13th century, we don’t actually know much about the timing and pace of events surrounding ahu construction and moai transportation in particular.

In his best-selling book of 2005 Collapse, Jared Diamond offered the social collapse of Easter Island (also known as Rapa Nui), around 1600, as a warning. Diamond controversially argued that the destruction of the island’s ecological environment set off a downward spiral of internal warfare, population decline, and cannibalism, ultimately resulting in a breakdown of social and political structures.

Challenging a narrative

Lipo has long challenged that narrative, arguing as far back as 2007 against the “ecocide” theory. He and Hunt published an article that year pointing out the lack of evidence of warfare on Easter Island compared to other Polynesian islands. There are no known fortifications and the obsidian tools found were clearly used for agriculture. There is also not much evidence of violence among the skeletal remains. He and Hunt concluded that the people of Rapa Nui continued to prosper long after 1600, which would justify a rethinking of the popular narrative that the island was destitute when Europeans arrived in 1722.

For their 2020 study, the team applied a Bayesian model-based method to existing radiocarbon dates collected from previous excavations at 11 different sites with ahu. That work generated mixed opinions from Lipo’s archaeological colleagues, with some suggesting that his team cherry-picked his radiocarbon dating, an accusation he dismissed at the time as “simply nonsense and ill-informed thinking.” They filtered their radiocarbon samples to only those they were confident were related to human occupation and human-related events, meaning they analyzed a smaller subset of all available ages (a not unusual strategy to eliminate bias). due to problems with ancient carbon) and the results because the colonization estimates were more or less the same as before.

Robert J. DiNapoli of Binghamton University stands next to a rock garden on Rapa Nui, or Easter Island.
Enlarge / Robert J. DiNapoli of Binghamton University stands next to a rock garden on Rapa Nui, or Easter Island.

Robert J. DiNapoli

The model also integrated the order and position of the island’s distinctive architecture, as well as ethnohistorical accounts, thus quantifying the start of monument construction, the pace at which it occurred, and when it likely ended. This allowed the researchers to test Diamond’s “collapse” hypothesis by constructing a more precise timeline of when construction took place at each of the sites. The results demonstrated a lack of evidence for pre-contact collapse and instead offered strong support for a new emerging model of resilient communities that continued their long-term traditions despite the impacts of European arrival.

New evidence

Now Lipo has returned with new findings that support his alternative theory, having analyzed the landscape to identify all the agricultural areas on the island. “We really wanted to see the evidence of whether the island could really support such a large number of people,” he said during a news conference. “What we know about the people who lived on the island before contact is that they survived on a combination of marine resources (fishing made up about 50 percent of their diet) and crops,” particularly sweet potato, as well as taro and yams.

He and his co-authors set out to determine how much food could be produced agriculturally, extrapolating from there the size of a sustainable population. The volcanic soil of Easter Island is highly eroded and therefore poor in nutrients essential for plant growth: mainly nitrogen, phosphorus and potassium, but also calcium, magnesium and sulfur. To increase yields, natives initially cut down the island’s trees to return nutrients to the soil.

When the trees were gone, they practiced a practice called “lithic mulching,” a form of rock gardening in which broken rocks were added to the top 20 to 25 centimeters (about 8 to 10 inches) of soil. This added essential nutrients to the soil. “We do it ourselves with non-organic fertilizers,” says Lipo. “We basically use machines to crush rocks into small pieces, which is effective because it exposes a large surface area. People on Rapa Nui do it by hand, literally breaking rocks and sticking them into the ground.”

Only one study was conducted in 2013 aimed at determining the capacity of the island’s rock garden, which was based on near-infrared bands from satellite images. The authors of that study estimated that between 4.9 and 21.2 km2 of the island’s total area was made up of rock gardens, although they acknowledged that this was probably an inaccurate estimate.

A map of results from the analysis of rock gardens on Easter Island.
Enlarge / A map of results from the analysis of rock gardens on Easter Island.

Carl Lipo

Lipo et al. examined satellite image data collected over the past five years, not only in the near-infrared, but also in the shortwave infrared (SWIR) and other visible spectra. SWIR is particularly sensitive at detecting water and nitrogen levels, making it easier to identify areas where lithic mulch occurred. They trained machine learning models on archaeological field identifications of rock garden features to analyze the SWIR data and make a new capacity estimate.

The result: Lipo et al. determined that the prevalence of rock gardening was about one-fifth of even the most conservative previous estimates of population size on Easter Island. They estimate that the island could be home to about 3,000 people, roughly the same number of inhabitants that European explorers found when they arrived. “Previous studies had estimated that the island was quite covered in mulch, leading to estimates of up to 16,000 people,” Lipo said. “We’re saying the island could never have supported 16,000 people; it didn’t have the productivity to do so. This pre-European collapse narrative simply has no basis in the archaeological record.”

“We don’t see a slowdown in demographic change in populations before the arrival of Europeans,” Lipo said. “All [cumulative] The evidence to date shows continued growth until a certain plateau is reached. It was certainly never an easy place to live, but the people were able to find a way to do it and lived within the limits of the island’s capacity until the arrival of the Europeans.” So, rather than being a warning, “Easter Island is a great example of how populations adapt to limited resources in a finite place, and do so in a sustainable way.”

DOI: Scientific Advances, 2024. 10.1126/sciadv.ado1459 (About DOIs).

Binghamton University archaeologist Carl Lipo has shed light on some of the ancient mysteries of Easter Island (Rapa Nui) through his ongoing research. Credit: Binghamton University, State University of New York

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