A new study published in the journal Frontiers in Ecology and Evolution examines the relationship between agricultural potential and population on Easter Island before the arrival of European explorers.
Easter Island is located some 3,512 km from Chile’s west coast and its nearest inhabited neighbor, Pitcairn Island, located some 2,075 km to the west. For reasons still unknown early Rapa Nui people began carving giant statues out of volcanic rock. Image credit: Marlene Hanssen.
Easter Island, also known as Rapa Nui, is located in the easternmost corner of the Polynesian Triangle and is one of the most isolated locations on Earth inhabited by humans.
The island has been surrounded in mystery ever since the Europeans first landed in 1722. Early visitors estimated a population of just 1,500-3,000, which seemed at odds with nearly 900 moais dotted around the island.
How did this small community construct, transport and erect these large rock figures? Dr. Cedric Puleston of the University of California, Davis, and colleagues hope to unravel this mystery by giving the best estimate yet of the maximum population size sustained by Easter Island in its heyday.
“Despite its almost complete isolation, the inhabitants of Easter Island created a complicated social structure and these amazing works of art before a dramatic change occurred,” Dr. Puleston said.
“We’ve tried to solve one piece of the puzzle — to figure out the maximum population size before it fell.”
“It appears the island could have supported 17,500 people at its peak, which represents the upper end of the range of previous estimates.”
“If the population fell from 17,500 to the small number that missionaries counted many years after European contact, it presents a very different picture from the maximum population of 3,000 or less that some have suggested.”
Rapanui people. Image credit: © Santiago Caruso.
Archaeological evidence implies the indigenous people numbered far greater than the 1,500-3,000 individuals encountered in the 18th century. In addition to internal conflict, the population crash has been attributed to ‘ecocide,’ in which the island’s resources were exhausted by its inhabitants, reducing its ability to support human life.
Dr. Puleston and co-authors examined the agricultural potential of the island before these events occurred, to calculate how many people Easter Island could sustain.
“We examined detailed maps, took soil samples around the Island, placed weather stations, used population models and estimated sweet potato production,” Dr. Puleston explained.
“When we had doubts about one of these factors we looked at the range of its potential values to work out different scenarios.”
The team found 19% of the island could have been used to grow sweet potatoes, which was the main food crop.
By using information on how birth and death rates at various ages depend on food availability, the researchers calculated the population size that level of production could sustain.
“The result is a wide range of possible maximum population sizes, but to get the smallest values you have to assume the worst of everything,” Dr. Puleston said.
“If we compare our agriculture estimates with other Polynesian Islands, a population of 17,500 people on this size of island is entirely reasonable.”
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Cedric O. Puleston et al. Rain, Sun, Soil, and Sweat: A Consideration of Population Limits on Rapa Nui (Easter Island) before European Contact. Front. Ecol. Evol, published online July 10, 2017; doi: 10.3389/fevo.2017.00069
