What the Easter Island myth is wrong

New research from Binghamton University and the State University of New York suggests that the population collapse at the heart of the Easter Island myth did not really happen.

You probably know this story, or a version of it: On Easter Island, locals cut down every tree, perhaps to make fields for agriculture or to erect giant statues in honor of their people. clans. This senseless move led to a catastrophic collapse, with only a few thousand remaining to see the first European ships land on their distant shores in 1722.

But has the demographic collapse at the heart of the Easter Island myth really happened? The answer, according to new research by Binghamton University anthropologists Robert DiNapoli and Carl Lipo, is no.

Their research, “Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island)”, was recently published in the journal Nature Communication. Co-authors include Enrico Crema of the University of Cambridge, Timothy Rieth of the International Institute for Archaeological Research and Terry Hunt of the University of Arizona.

Easter Island, or Rapa Nui in the native language, has long been a center of study on issues related to environmental collapse. But to resolve these questions, researchers must first reconstruct the island’s population levels to determine if such a collapse has occurred and, if so, its scale.

“For Rapa Nui, much of the scholarly and popular discussion on the island has focused on the idea that there has been a demographic collapse, and that it is correlated over time with climate change and changes. environmental, ”explained DiNapoli, postdoctoral associate researcher in environmental studies and anthropology.

Some time after its colonization between the 12th and 13th centuries AD, the once wooded island was stripped of trees; most often, researchers report human-induced clearing for agriculture and the introduction of invasive species such as rats. These environmental changes, the argument goes, reduced the carrying capacity of the island and led to population decline.

In addition, around the year 1500, there was a climate change in the Southern Oscillation Index; this change has led to a drier climate on Rapa Nui.

“One argument is that the changes in the environment have had a negative impact. People see that there has been a drought and said, ‘Well the drought caused these changes,” said Lipo, professor. of Anthropology and Environmental Studies and Associate Dean of Harpur. University. “There are changes. Their populations are changing and their environment is changing; over time the palm trees have been lost and in the end the climate has dried up. But do these changes really explain what we see in them? population data through radiocarbon dating? “

Reconstructing demographic changes

Archaeologists have different ways of reconstructing the sizes of populations using indirect measurements, such as examining the different ages of individuals at burial sites or counting ancient house sites. The latter measure can be problematic because it makes assumptions about how many people live in each house and whether the houses were occupied at the same time, DiNapoli said.

The most common technique, however, uses radiocarbon dating to track the extent of human activity at any given time and extrapolate population changes from that data. But the radiocarbon dates may be uncertain, DiNapoli admitted.

For the first time, DiNapoli and Lipo presented a method capable of both resolving these uncertainties and showing how changes in population size are related to environmental variables over time.

Standard statistical methods do not work when it comes to relating radiocarbon data to environmental and climate change, and associated population changes. To do this, it would be necessary to estimate a “likelihood function”, which is currently difficult to calculate. Rough Bayesian calculus, however, is a form of statistical modeling that does not require a likelihood function, and thus offers researchers a workaround, DiNapoli explained.

Using this technique, the researchers determined that the island had experienced constant population growth from its initial colonization until European contact in 1722. After that date, two models show a possible population plateau, while two other models show a possible decline.

In short, there is no evidence that the islanders used the now-extinct palm trees for food, a key point in many collapse myths. Current research shows that deforestation has been prolonged and has not resulted in catastrophic erosion; the trees were eventually replaced by stone mulched gardens which increased agricultural productivity. During times of drought, people may have relied on coastal freshwater seeps.

The construction of the moai statues, seen by some as a contributing factor to the collapse, in fact continued even after the arrival of Europeans.

In short, the island had never had more than a few thousand inhabitants before European contact, and their numbers were increasing rather than decreasing, their research shows.

“These resilience strategies have been very effective, despite the fact that the climate has dried up,” Lipo said. “These are very good arguments in favor of resilience and sustainability. “

Bury the myth

Why, then, does the popular narrative of the Easter Island collapse persist? It probably has less to do with the ancient Rapa Nui people than with ourselves, Lipo explained.

The concept that changes in the environment affect human populations began to take off in the 1960s, Lipo said. Over time, this focus has become more intense, with researchers beginning to view changes in the environment as the primary driver of cultural change and transformation.

But this correlation may come more from modern concerns about pollution and climate change induced by industrialization, rather than archaeological evidence. Environmental changes, Lipo points out, occur at different timescales and to different magnitudes. The way in which human communities respond to these changes varies.

Take a classic example of resource overexploitation: the collapse of the Northeastern cod fishery. While the economies of individual communities may have collapsed, larger harvesting efforts have simply moved halfway around the world.

On a remote island, however, sustainability is a matter of the very survival of the community and resources tend to be managed conservatively. A misstep in resource management could lead to tangible and catastrophic consequences, such as famine.

“The consequences of your actions are immediately obvious to you and to everyone around you,” Lipo said.

Lipo acknowledged that supporters of the Easter Island collapse story tend to see him as a climate change denier; This is absolutely not the case. But he warned that the way ancient peoples handled climate and environmental change does not necessarily reflect current global crises and their impact in the modern world. In fact, they can teach us a lot about resilience and sustainability.

“There’s a natural tendency to think that the people of the past aren’t as smart as us and kind of made all of these mistakes, but it’s really the opposite,” Lipo said. “They produced offspring and the success that created the present. While their technologies may be simpler than ours, there is so much to learn about the context in which they were able to survive.”