June 4 (UPI) -- New analysis suggests Easter Islanders used ramps and a rope-powered pulley system to place stone hats atop the heads of their famed statues.
"Of the many questions that surround the island's past, two tend to stand out: How did people of the past move such massive statues, 'moai,' and how did they place such massive stone hats, 'pukao,' on top of their heads?" Carl Lipo, a professor of anthropology at Binghamton University, said in a news release.
Pukao are the hat-like, stone cylinders made of red scoria found atop the heads of moai. Some of the stone hats weigh up to 12 tons.
"We've learned they moved the statues in a walking fashion using simple, physics-based processes, in a way that was elegant and remarkably effective," Lipo said. "Our latest study now tackles the issue of the hats. These multiton stone objects were carved at a separate quarry, transported across the island and somehow raised to the top of the heads of the statues."
Scientists previously imagined all the different ways -- wooden ramps, piles of stones -- the stone hats might have been placed atop the statues. But the latest analysis looked to narrow down the possibilities and isolate those that best matched the archaeological data.
"Different possible transport methods constrain aspects of pukao variability in different ways," said Sean Hixon, a graduate student at Penn State University.
Hixon and his research partners determined the Rapa Nui people likely rolled the stone hats from the quarry to the location of the statues. Once at the base of the moai, the pukao were rolled up ramps using a parbuckling system.
"In parbuckling, a line would have been wrapped around the pukao cylinder, and then people would have pulled the rope from the top of the platform," Lipo said. "This approach minimizes the effort needed to roll the statue up the ramp. Like the way in which the statues were transported, parbuckling was a simple and elegant solution that required minimum resources and effort."
Researchers suggest the latest findings -- published in the Journal of Archaeological Science -- offer additional proof of the Rapa Nui people's ingenuity.
Historically, scholars characterized the Rapa Nui people as irrational and reckless. Historians blamed the collapse of Easter Island society on a misuse of resources. But newer studies suggest the people of Easter Island were, in fact, adaptive and peaceful, capable of maintaining sustainable food systems from land and sea, despite limited natural resources.
"These were quite sophisticated people who were well tuned to the requirements of living on this island and used their resources wisely to maximize their achievements and provide long-term stability," Lipo said.