The question of how statue makers hundreds of years ago affixed the “hats” perplexed undergraduate student Sean Hixon, so much so that he made the puzzle the focus of his 2015 honors thesis.
EUGENE, Ore. — A University of Oregon anthropology student — with an unlikely assist from his physics professor — might have helped solve one of the many mysteries of the iconic statues on Easter Island.
Some of the island’s stone statues have large cylinders weighing nearly 13 tons atop their heads. The question of how statue makers hundreds of years ago affixed the “hats” perplexed undergraduate student Sean Hixon, so much so that he made the puzzle the focus of his 2015 honors thesis.
His theory: Easter islanders built ramps, wrapped the hats in rope and pulled them up to the top of the statues, some as tall as 30 feet.
“Before our study, no one had really looked at the hats themselves and at the archeological record for details that might show that one method of transport was more plausible than another,” he said.
Hixon, who graduated from Oregon in 2015, happened to take a physics class while in Eugene, and in it, he discovered the mathematical tools to figure out a solid Easter Island hat hypothesis. The results of Hixon’s thesis form the basis for a study that appeared earlier this year in the Journal of Archaeological Science.
While a great mystery, the physics problem didn’t prove to be too difficult, said Ben McMorran, an assistant professor who taught Hixon’s Physics 252 class.
“It turned out to be much simpler than either of us expected,” he said. “We got a nice, simple formula to describe what forces would need to be applied to roll (the hats) up.”
Starting about 800 years ago, inhabitants of the island in the mid-Pacific Ocean erected about 900 monuments with large noses and elongated faces. The island and its people are also known as Rapa Nui. Previous research has determined that the islanders likely “walked” the statues — that is, wiggled them along like giant refrigerators — onto platforms using ropes tied to the tops.
As for the hats — which were carved from dark red volcanic rock, were up to 9 feet around, and might have also depicted hair — the consensus had been that ramps were unlikely. Pushing the cylinders up would have required very long ramps. And the people doing the pushing would have been in harm’s way as they shoved the hats upward.
Hixon, now a graduate student at Penn State University, traveled to Easter Island in 2014 with Terry Hunt, former dean of the University of Oregon’s Clark Honors College. Along with another researcher, they took about 15,000 photos of the hats and cylinders and began to ponder how the heavy objects made it to the top of the statues.
Hixon and McMorran later filled a white board with diagrams and formulas to show that ramps probably were the key to capping the statues after all.
The islanders likely used parbuckling, a technique used by loggers to load logs onto trucks and by sailors to heft barrels onto a boat, McMorran said. A rope wraps around the cylinder, which is pulled from the top to roll it up a ramp.
Crunching the numbers, Hixon and McMorran found that a small group, about a dozen people or so, could have moved each hat up a 30-degree slope. The ramps on Easter Island were likely 60 to 90 feet long. Hixon created three-dimensional models to evaluate the physics formula.
McMorran still gets excited talking about how his physics class played a part in Hixon’s thesis.
“I was ecstatic because this is exactly what I was going for,” he said. He hopes that his students apply physics elsewhere in their lives and not focus only on passing tests, he said.
Theorizing about the hats has made McMorran want to visit Easter Island. But seeing the statutes in person won’t necessarily confirm the calculations. The hats still hold some mystery.
“It’s impossible to know for sure without a time machine,” McMorran said.
Dylan Darling is a reporter for The Eugene (Ore.) Register-Guard.