Easter Island's population never collapsed because it never got that big, researchers suggest

The island of Rapa Nui, also known as Easter Island, never had a catastrophic population collapse, a new study proposes. 

The finding may upend decades of assumptions about how overexploitation of the landscape by the Indigenous people of Rapa Nui, known as the Rapanui, caused a supposed rapid rise and catastrophic fall before any Europeans arrived. The research, which used a type of artificial intelligence called machine learning, suggests that the Rapanui population was sustainable, never going above 3,900 people. However, experts who were not involved in the study have critiqued the research, pointing out weaknesses in the data.

Located over 2,300 miles (3,700 kilometers) from the nearest mainland, Rapa Nui is one of the world's most remote locations to be inhabited by people. Rapa Nui was first settled around 1000 A.D., likely by people from Polynesia, who regularly traded with people living on the South American continent. Famous for its moai — giant stone statues of human figures — Rapa Nui is also known for palm tree deforestation and the overexploitation of resources, which have been cited as major factors in the decline and collapse of Rapanui culture.

While it is true that the small island — which is just 63 square miles (164 square kilometers), or slightly smaller than Washington, D.C. — has poor soil quality and limited freshwater resources, researchers have discovered that the story of the Rapanui is one of survival in challenging ecological conditions. 

One method the Rapanui used to enhance the island's volcanic soil was "lithic mulching," or rock gardening, in which pieces of rock were added to cultivation areas to boost productivity. The rock gardens generated better airflow in the soil, helping mediate temperature swings and maintaining nutrients — including nitrogen, phosphorus and potassium — in the soil. 

Archaeologists have researched both rock gardening and soil fertility on Rapa Nui to better understand food cultivation and historical land usage, including quarrying for the creation of moai. While some experts have suggested that the island may have been able to support 16,000 Rapanui people at its height in the 15th century, the new study has reevaluated the population size, suggesting it was never more than 3,900 people.

Related: Polynesians and Native Americans paired up 800 years ago, DNA reveals