The people of Easter Island may have adorned their monumental statues with massive stone ‘hats’ by rolling the headgear up gentle ramps.

The iconic statues of Easter Island, which is also known as Rapa Nui, were built after people reached the island in the thirteenth century. Sean Hixon at Pennsylvania State University in University Park and his colleagues sought to understand how the hats — the heaviest of which weighs nearly 12 tonnes — were hefted onto the lofty statues.

Examination of 50 hats showed that almost all are cylindrical, and so easy to roll. Their bases are not scratched, suggesting that they were not slid into place. Rocky debris near the statues could have formed ramps that were later incorporated into the statues’ supportive platforms.

The authors calculate that groups of just 10–15 people could have heaved the massive headgear up the ramps by pulling plant-fibre ropes looped around the hats.