Everybody who’s ever seen the huge stone heads (moai) of Easter Island has wondered how they could possibly have been moved into place. Nearly 1,000 of these giant busts litter the island — about half near the seashore, facing inland. The tallest is about 10 meters (33 feet) tall, and weighs 82 tons; the heaviest was shorter and weighs 86 tons.
The vast majority (about 95%) of the moai were carved in the crater of Rano Raraku, near one corner of the roughly-triangular island. This means that many of the figures had to be moved — somehow — for dozens of kilometers.
To date, the prevailing theory for how they were moved has been via some sort of combination of rollers and sledges. Here’s a clip from a 1998 experiment conducted to test this theory out (direct link):
But the local oral tradition is that the statues “walked” to their current locations. Barring some metaphysical transformation, how could this have happened?
Archaeologists Carl Lipo (of California State University, Long Beach) and Terry Hunt (of the University of Hawaii in Honolulu) proposed an approach. In their new theory, the statues did walk to their final sites — but they had help, in the form of three teams of people with ropes. Given that the statues have flat bottoms, they could be moved upright along a smooth dirt road, using a rocking / twisting motion. To test this out, they used a replica (admittedly smallish) moai and a level path (direct link):
Adherents of the sledge / roller technique are skeptical — noting the relatively small size of the test moai and it’s not-quite-true-to-facts bottom shape. But supporters of the upright move technique note that it fits what’s seen at the site. Damaged moai have been found abandoned along ancient roads — statues along downhill roads are found face-down, while those abandoned along uphill roads are found face-up.
More interesting background to be found on Nature here.