How Easter Island statues got their hats

The famous statues of Rapa Nui, or Easter Island, are best known for their deep-set eyes and long ears. They also sport impressive multi-tonne hats made from a different rock type. Quite how these pukao, as they are known, were transported and placed atop the statues has long been a puzzle. But Prof Terry Hunt, from the University of Arizona, says researchers think they now have a clearer understanding.