Researchers in the US believe they have cracked one of the biggest mysteries surrounding the famous stone sculptures that populate Easter Island near Chile.

There are over 900 known Moai statues – or ahu – on the Pacific island and their existence has puzzled archaeologists since Europeans first landed.

Researchers have made a number of breakthroughs in recent years in terms of how and why the monuments were constructed.

However a new study published in the journal PLOS One claims to have answered one of the most puzzling questions – why the statues are placed where they are.

Researchers focused on an eastern area of the island and, by comparing the placement of the statues with the island's natural resources, they found that the structures were placed near sources of fresh water.

Moai statues on Easter Island. Image: Ben Holtam Flickr

Drinking water

One of the study’s co-authors, Professor Carl Lipo from Binghamton University in New York, told The Guardian that he and his colleagues were interested in where the island’s inhabitants got their drinking water from as it has no permanent streams.

He said there is little evidence to suggest they relied on the islands lakes; however, he said fresh water does flow through the ground in aquifers which seep into caves and flow into the sea.

“It is sort of amazing at low tide when the water goes down, suddenly there are streams running off at different spots right at the coast that are just pure fresh water,” he said.

“We noticed this, actually, when we were doing a survey on the island - that we would see horses drinking from the ocean.”

Professor Lipo said that historic wells were found at sites that apparently did not have fresh water.

The research provides the best explanation yet for why the structures are found inland as well as on the coast.

A view of a Moai stone statue at sunset on Easter Island, 09-07-2018. Image: Wang Pei/Xinhua News Agency/PA Images

Moai

The island’s inhabitants are believed to have begun building the monuments - which are believed to represent significant ancestors - in the 13th century.

Their huge size led academics to believe that the island must have once supported a far larger and more complex society which collapsed following the destruction it’s natural ecosystem.

However, recent studies have found that their construction “required neither large numbers of individuals nor trees.”

The authors of this latest study said the implications of this are far-reaching - as they put paid to the common assumption that the construction of the monuments involved complex social organisation and labour management.

They said it also undermines the assumption that their construction must have led to the environmental destruction of the island through deforestation and land erosion.

Professor Lipo said there is little evidence to support the once-commonly-held view that the islanders were constantly at war over scant natural resources.

He said this latest study adds weight to theory that communities interacted through monument building – with the team now studying whether the size or features of the statues are linked to the quality of nearby water sources.