Pukao are large, cylindrical stones made from a volcanic rick known as red scoria. Weighing multiple tons, they were placed on the heads of the moai during prehistoric times, consistent with the Polynesian tradtions of honoring their ancestors. Photo: Carl Lipo

The moai of Easter Island, ancient and massive statues carved from volcanic rock, have mystified historians and archaeologists for centuries. It was only recently that stone circles made of lighter red scoria stone were identified as being hats for some of the monuments, erected to deified dead ancestors of the Rapa Nui peoples.

Now a team of scientists describe new carvings on these megalithic hats that have started to better describe the importance of the sculptures to the Rapa Nui before the arrival of Europeans in the 18th century.

The paper appears in a recent issue of Advances in Archaeological Practice, and is co-authored by authors from Binghamton University, Penn State and other schools.

“With the building mitigating any sense of conflict, the moai construction and pukao placements were key parts to the success of the island,” said Carl Lipo, an anthropologist from Binghamton. “In our analysis of the archaeological records, we see evidence that demonstrates the prehistoric communities repeatedly worked together to build monuments. The action of cooperation had a benefit to the community by enabling sharing of information and resources.”

The team looked at 70 of the hats, called “pukao” and which weighed multiple tons each, despite their being relatively “light” in comparison to the full figures. Fifty of them which had once been on the heads of the moai were analyzed, as well 13 pukao located in the island’s red stone quarry called Puna Pau.

The technique was a photogrammetric technique called Structure from motion (SfM) mapping. Essentially, the 2-D images are combined, compared and contrasted to produce a 3-D model of a surface. In this case, the hyper-detailed look allowed the investigators to determine more markings on the rock than ever before.

The conclusion was that the abundance of petroglyphs meant that the statues were a focal point of the society.

But those carvings were also degrading constantly – and need to be studied soon, or else the clues they hold will be lost forever, they write.

“Every time we look at the archaeological record of the island, we are surprised by what we find,” added Lipo. “There is much more to be learned from this remarkable place – important answers that shed light on the abilities of our ancestors, as well as potential ideas for contemporary society about what it takes to survive on a tiny and remote island.”