Simple physics and techniques were used to place very heavy stone hats on the statues from Easter Island. Credit: Sean Hixon / Penn State
How did they put 13-ton stone hats on the Easter Island statues - science news in brief

The giant statues from the Easter Island hold many secrets, but one of them might have been solved by a new study. Scientists have been trying to understand how did the ancient builders managed to position huge stone hats, sometimes weighing 13 tonnes, on the heads of the statues. It turns out that the hats were rolled up on large ramps to the top of a standing statue using a technique called parbuckling. The study estimates that using this simple approach, a team of only 15 workers could have performed the delicate operation. After this step, the hats were sculptured into their final form, then levered and pivoted into the final position. 

Read the full story: Pennsylvania State University
Scientific publication: Journal of Archaeological Science