Anthropologist Carl Lipo of the University of Birmingham has spent years studying the statues on Easter Island. He says the moai were often mounted on a base called an ahu. Today on Easter Island, you can find ahu without moai and moai without ahu, especially along the roads leading to the ahu. He suggests they were probably transported but never reached their destination, leading to the “some are there and some are not there” situation.
In 2012, Lipo and Terry Hunt, a researcher at the University of Arizona, discovered that a 10-foot-tall (3-meter-tall), 5-ton moai statue could be moved several hundred meters with just 18 people and three large ropes that used a rocking motion.
Last year, Lipo also proposed a theory about how the islanders placed the red stone caps on the heads of some of the moai. They used ropes to pull the 13-ton caps up a slope to place them on the heads of the statues.Now, Lipo and his colleagues have turned their research to the meaning of the placement of the statues and their bases. If they had a symbolic or ceremonial meaning, they would have been placed in more prominent places, such as on top of hills, so that people could see them. But the moai and ahu are located along the coast and they are not evenly distributed. Over 20 years of field research, Lipo found that there were locations that he thought were ideal for the ahu bases, but in fact there were no ahu in the places he chose. So there must have been some other reason why the first inhabitants of the island chose certain areas to place these giant statues.
Working with a hydrologist in Hawaii, Lipo realized that fresh water is the most valuable resource on an island, and it has a big impact on where people live and where statues are placed. Hawaii’s volcanic islands have an unusual property: fresh water often flows along the channels created by lava flowing into the ocean. “There are actually underground springs offshore,” Lipo says. “Fishermen know where there is fresh water in the middle of the ocean.”
Freshwater is also a scarce resource on Easter Island. Noticing this similarity, Lipo and graduate student Tonya Broadman decided to explore the waters of Easter Island. Based on measurements of the salinity of the coastal waters, they discovered: “When the tide goes out, the seawater gradually recedes, and the freshwater immediately flows out to the shore,” Lipo said. Many European explorers who set foot on the island when the first inhabitants were still there also recorded this phenomenon.
Lipo and Broadman meticulously mapped the locations of freshwater sources around the island, and wherever they marked freshwater sources close to shore, they found ahu. They also used a technique called quanтιтative spatial modeling to show that this water map was plausible, not just a perception. Although freshwater pools and lakes do exist on the island, archaeological evidence shows no evidence of houses or settlements around these areas.
(A) Location of ahu, (B) Location of fresh water sources, (C) Location of rich marine resources, (D) (E) (F) Classification of rock cover layers respectively
In addition, Lipo also applied the same model to examine other natural resources on the island to prove the hypothesis because many other things that support life are located near the coast. However, based on statistical analysis, he argued that fresh water is the most important factor in determining the location of ahu and moai compared to other factors.
The red dots are ahu.
Robert DiNapoli of the University of Oregon, co-author of the study, said: “Many researchers, including ourselves, have long suspected that ahu/moai are ᴀssociated with various types of resources, such as water, agricultural land, and seafood availability. However, these ᴀssociations have never been quantified or demonstrated statistically. Our study, with its quanтιтative spatial model, clearly shows that ahu are ᴀssociated with freshwater but not with other resources.”
Meanwhile, Terry Hunt said the data collected so far showed that the island’s first inhabitants survived for more than 500 years by building multiple communities around limited resources and fostering a sharing economy. It was the arrival of European colonists that disrupted their way of life, contributing to the collapse of their society. Lipo and his colleagues will return to Easter Island in May to continue their fieldwork, having so far only mapped the freshwater sources on the western side of the island. A comprehensive survey will hopefully answer the question of why the islanders spent so much time and effort building ahu and moai.
Lipo says: “We will probably never have a definitive answer because there are many reasons why people on the island created the statues… As we began to see resource constraints, we saw that the island communities were very much tied to the local resources. They survived by cooperation and the statues served as community markers.”
