The Mystery of How Easter Island Statues Got Their Colossal Hats Might Finally Be Solved

Science Alert - It's a towering problem, one to stump the most determined of milliners. You've carved almost 1,000 immense statues standing up to 10 metres (33 ft) tall. And now you want to put their hats on.

 There's just one problem. The hats, like the graven colossi themselves, are hewn out of solid rock, and weigh several tonnes a piece. How on Earth could you ever lift and fit this hulking headwear?

This ancient puzzle is just one of many posed by the strange stone legacy of Easter Island, whose unflinching moai statues maintain their silent vigil long centuries after the mysterious collapse of the Polynesian Rapa Nui society that erected them.

"Of the many questions that surround the island's past, two tend to stand out," explains anthropologist Carl Lipo from Binghamton University.

"How did people of the past move such massive statues, and how did they place such massive stone hats (pukao) on top of their heads?"

Researchers already solved the first part of the puzzle. For decades, archaeologists have experimented with various methods of 'walking' the moai - rocking replica statues from side to side along prepared paths, ever slowly inching the towering figures forward.

It's kind of like shuffling a fridge into a new kitchen (although decidedly more epic).

But what about the world's heaviest hats?

In a new study, Lipo and his team suggest that the cylindrical pukao - with diameters up to 2 metres (6.5 feet) and weighing 12 tonnes - may have been rolled across the island from the red scoria quarries they were cut from.

That's how they were transported to the moai, but to lift them onto the statues' elevated heads, props - and a little physics trickery - would be needed, with a ramp-and-ropes technique...