A new theory on the fate of Easter Island, now known by its native name of Rapa Nui — meaning “navel of the world” — posits that rats and outsiders, not the environmental depredations of its native people, caused the depletion of the island’s resources and the shrinking of its human population.

For two and a half centuries, Easter Island has been famed for its moai statues, tall stone heads with elongated features that are found across the island. The island has become a parable of human excess and environmental catastrophe: its inhabitants are alleged to have destroyed the forest cover, depleting their food sources and shelter and eventually leaving themselves unable to build canoes.

Jared Diamond’s recent book Collapse calls Rapa Nui “the clearest example of a society that destroyed itself by overexploiting its own resources”.Some scholars have termed this “ecocide”: a self-inflicted depletion of the enviroment to a point of no return, and see in the example of Rapa Nui a warning for us all.

Yet rats, rather than people, may have been the crucial factor on Rapa Nui, according to the archaeologist Terry Hunt, of the University of Hawaii. He notes that the Pacific rat, Rattus exulans, arrived as a commensal animal with human settlers, possibly as a fast-breeding source of protein for voyagers.

Dr Hunt believes that the impact of the rat on the forests of Rapa Nui was devastating. In the Journal of Archaeological Science, using comparative data from Hawaii, where all but a few islands have been ravaged by rats, he estimates that “the rat population of Rapa Nui could have exceeded 3.1 million within a very short time following their introduction”.

One of the most important plants, the giant Jubaea palm tree, now extinct on Rapa Nui, yields a hard-shelled nut: every example found in cave deposits had been gnawed and rendered infertile. Hunt suggests that this, together with nibbling of the seedlings, effectively halted regeneration of the forest cover, while “a large rat population would also prey directly upon nesting seabirds, land-birds” and other species, contributing to their extinction.

Archaeological evidence from Hawaii shows that forest decline, apparently because of rats and measured by falling tree pollen counts, preceded the human impact of clearance and burning.

Hunt argues that settlers arrived on Rapa Nui much later than has hitherto been believed. While a new consensus has been building for an arrival around AD 700-800, Hunt’s excavations at Anakena, on the north side of Rapa Nui, suggest settlement as late as 1200. The palaeoenvironmental record shows that deforestation occurred over about 400 years between 1250 and 1650, with remnants of forest lasting into historic times, with the human population rising, he suggests, to a maximum of about 4,000 by AD 1370. There is no evidence for a large and unsustainable population of 15,000 or more as Diamond claims.

Such a large total, followed by a “crash”, “is critical to notions of ecocide, and despite repeated claims, Rapa Nui does not appear to represent a case of ecocide,” Dr Hunt says. “The documented population collapse for Rapa Nui occurred as a result of European contacts, with Old World diseases and slave-trading.” Journal of Archaeological Science 34: 485-502.