‘Coral houses’ are dotted throughout the Pacific. Now scientists know exactly when they were built

Facade of a house on Akamaru Island, French Polynesia. Associate Professor James Flexner, University of Sydney

The Mangareva Islands are about 1,600 kilometres southeast of Tahiti in French Polynesia. They get their name (which means “floating mountains”) from the way the sea spray breaking on the surrounding coral atolls, or motu, causes the ancient volcanic peaks to appear as if they are floating above the waves.

Today, the islands are home to about 2,000 people, many of whom work on the pearl farms in the idyllic turquoise lagoon. Dotted across the islands are the remains of dozens of remarkable pieces of architecture: homes built from coral.