About 1,000 years ago, a small group of Polynesians sailed thousands of miles across the Pacific Ocean and settled on a small, previously uninhabited island named Rapa Nui, one of the most isolated regions in the world. There they erected hundreds of “moai,” or giant stone statues, now famous symbols of a lost civilization. Eventually their numbers grew to unsustainable levels. They cut down all the trees, killed seabirds, depleted the soil, and ultimately destroyed the environment. When Europeans discovered the island in 1722 and called it Easter Island, their population and civilization collapsed, with only a few thousand remaining. At least that’s the old story told in academic studies and popular books like Jared Diamond’s 2005 “Collapse.”
A new study challenges this ecocide narrative, saying Rapa Nui’s population never soared to unsustainable levels. Instead, settlers found ways to cope with the island’s strict limits and maintained a small, stable population for centuries. Evidence: A newly elaborate inventory of the ingenious “rock gardens” where islanders grew nutritious sweet potatoes, a staple of their diet. Researchers said the gardens covered just enough area to support thousands of people. research It was recently published in the journal Science Advances.
“This shows that the population could not have been as large as previous estimates,” the lead author said. Dylan Davis, a postdoctoral researcher in archeology at the Columbia Climate School. “The lesson is the opposite of collapse theory. “People have been able to be very resilient in the face of limited resources by modifying their environment in helpful ways.”
Easter Island is arguably the most remote inhabited place on Earth and one of the last places to be settled by humans. The nearest continental landmass is central Chile, nearly 2,200 miles to the east. About 3,200 miles to the west are the tropical Cook Islands, where settlers are thought to have sailed from around 1200 AD.
The 63-square-mile island is made entirely of volcanic rock, but unlike lush tropical islands such as Hawaii and Tahiti, eruptions stopped hundreds of thousands of years ago, and the mineral nutrients brought by the lava have long since eroded from the soil. Located in the subtropics, this island is drier than tropical islands. Making the situation more difficult, the surrounding waters drop steeply, meaning islanders have to work harder to harvest marine life than those living on Polynesian islands surrounded by accessible and productive lagoons and coral reefs.
To cope, settlers used a technique called rock gardening, or rock mulching. It consists of rocks scattered on low-lying surfaces that are at least partially protected from salt spray and wind. I planted sweet potatoes in the crevices of the rocks. Studies have shown that rocks ranging from the size of golf balls to large boulders disrupt dry winds and create turbulence, lowering maximum surface temperatures during the day and increasing minimum surface temperatures at night. Small pieces broken by hand expose a fresh surface full of mineral nutrients that are released into the soil as it weathers. Some islanders still use gardens, but despite all this labor, productivity is minimal. This technique was also used by indigenous people in New Zealand, the Canary Islands, and the southwestern United States.
Some scientists have argued that, in part because of the giant moai, the island’s population must have once been much larger than the 3,000 or so inhabitants first observed by Europeans. The inference is that it would have taken a lot of people to build it. Therefore, in recent years researchers have attempted to estimate these populations in part by examining the extent and productive capacity of rock gardens. Early Europeans estimated that they occupied 10% of the island. 2013 study Results based on visual and near-infrared satellite imagery ranged from 2.5% to 12.5%. Both of these spectra have a wide margin of error because they only distinguish between rock and plant areas, not gardens. Other study in 2017 Approximately 7,700 acres (19% of the island) have been identified as suitable for growing sweet potatoes. Using various assumptions about crop yields and other factors, studies estimate that the past population may have been as high as 17,500 or even 25,000, but may have been much lower.
In the new study, the research team conducted fieldwork on rock gardens and their characteristics over a five-year period. They then used this data to train a series of machine learning models to detect gardens through satellite imagery tuned to the newly available shortwave infrared spectrum. This spectrum highlights places with high soil moisture and nitrogen, key features of the garden, as well as rock formations.
Researchers concluded that the rock garden covers only about 188 acres (less than 0.5% of the island). They say they may have missed the little things, but not enough to make a big difference. Making a series of assumptions, they say the garden would have supported about 2,000 people if the entire diet had been based on sweet potatoes. However, isotopes found in bones and teeth and other evidence suggest that people in the past probably obtained 35 to 45 percent of their diet from marine sources, with smaller amounts from other less nutritious crops such as bananas, taro and sugar cane. . . Taking these sources into account, the population carrying capacity would have increased to about 3,000, the number observed during contact with Europeans.
“There are natural rock outcrops here and there that in the past were mistaken for rock gardens. Shortwave images give a different picture,” Davis said.
cal lipoIdeas about population booms and busts “are still permeating the public mind and fields including ecology, but archaeologists are quietly moving away from them,” said Binghamton University archaeologist and co-author of the study. Accumulated evidence based on radiocarbon dating of artifacts and human remains does not support the idea of huge populations, he said. “People’s lifestyles would have been incredibly difficult,” he said. “Imagine sitting around breaking rocks all day.”
The island’s population now stands at nearly 8,000 (with about 100,000 more tourists per year). Although most food is now imported, some residents still grow sweet potatoes in their ancient gardens. This is a practice that grew during the pandemic-induced lockdowns of 2020-2021, when incomes were limited. Some have also switched to mainland agricultural techniques, soil cultivation and application of artificial fertilizers. But this would not be sustainable because it would further deplete the thin soil cover, Lipo said.
Seth Quintus, an anthropologist at the University of Hawaii who was not involved in the study, said he sees the island as “a good case study in human behavioral adaptation in the face of a dynamic environment.” The new study and others like it “offer an opportunity to better document the nature and extent of adaptive strategies,” he said. “Surviving in the drier, subtropical regions of Rapa Nui, which are more isolated and geologically older, was a real challenge.”
The study was also co-authored by Robert DiNapoli of Binghamton University. Gina Pakarati, an independent researcher on Rapa Nui; and Terry Hunt of the University of Arizona.
