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For years, researchers have puzzled over how the ancient people of Rapa Nui did the seemingly impossible and moved their iconic moai statues. Using a combination of physics, 3D modeling and on-the-ground experiments, a team including faculty at Binghamton University, State University of New York, has confirmed that the statues actually walked—with a little rope and remarkably few people.

Studying nearly 1,000 moai statues, Binghamton University Professor of Anthropology Carl Lipo and the University of Arizona's Terry Hunt found that the people of Rapa Nui likely used rope and "walked" the giant statues in a zig-zag motion along carefully designed roads. The paper is in the Journal of Archaeological Science.

Lipo and his colleagues had previously demonstrated via experimental evidence that the large statues "walked" from their quarry to ceremonial platforms using an upright, rocking motion, challenging a theory that the statues were moved lying prone on wooden devices.

"Once you get it moving, it isn't hard at all—people are pulling with one arm. It conserves energy, and it moves really quickly," said Lipo. "The hard part is getting it rocking in the first place. The question is, if it's really large, what would it take? Are the things that we saw experimentally consistent with what we would expect from a physics perspective?"

To explore how a larger statue might move, Lipo's team created high-resolution 3D models of the moai and identified distinctive design features—wide D-shaped bases and a forward lean—that would make them more likely to be moved in a rocking, zig-zagging motion.

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Putting their theory to the test, the team built a 4.35-ton replica moai with the distinct "forward-lean" design. With just 18 people, the team was able to transport the moai 100 meters in just 40 minutes, a marked improvement over previous vertical transport attempts.

"The physics makes sense," said Lipo. "What we saw experimentally actually works. And as it gets bigger, it still works. All the attributes that we see about moving gigantic ones only get more and more consistent the bigger and bigger they get, because it becomes the only way you could move it."

Adding to the support for this theory are the roads of Rapa Nui. Measuring 4.5 meters wide with a concave cross-section, the roads were ideal for stabilizing the statues as they moved forward.

"Every time they're moving a statue, it looks like they're making a road. The road is part of moving the statue," said Lipo. "We actually see them overlapping each other, and many parallel versions of them. What they are probably doing is clearing a path, moving it, clearing another, clearing it further, and moving it right in certain sequences. So they're spending a lot of time on the road part."

Lipo said that nothing else currently explains how the moai were moved. The challenge to anyone else is to prove them wrong.

"Find some evidence that shows it couldn't be walking. Because nothing we've seen anywhere disproves that," said Lipo. "In fact, everything we ever see and ever thought of keeps strengthening the argument."

Lipo said Rapa Nui is notorious for wild theories backed by zero evidence. This research is an example of putting a theory to the test.

"People have spun all kinds of tales about stuff that's plausible or possible in some way, but they never go about evaluating the evidence to show that, in fact, you can learn about the past and explain the record that you see in ways that are fully scientific," said Lipo. "One of the steps is simply saying, 'Look, we can build an answer here.'"

Lipo said that the research also honors the people of Rapa Nui, who achieved a monumental engineering feat with limited resources.

"It shows that the Rapa Nui people were incredibly smart. They figured this out," said Lipo. "They're doing it the way that's consistent with the resources they have. So it really gives honor to those people, saying, look at what they were able to achieve, and we have a lot to learn from them in these principles."