He points out that climate data obtained from slow-growing corals around the Pacific indicate a series of unusually frequent El Ninos around the time of the Lapita expansion.

Within the span of several centuries, the Lapita stretched the boundaries of their world from the jungle — clad volcanoes of Papua New Guinea to the loneliest coral outliers of Tonga.

I was heading for Aitutaki, which, with its palm-fringed coral lagoon, is the archetypal tropical island.