A scenario blaming rats for the devastation of Easter Island doesn't account for recent results, argues Paul Bahn.
The Statues That Walked: Unraveling the Mystery of Easter Island Terry Hunt and Carl Lipo. Free Press: 2011. 256 pp. $26
Easter Island, or Rapa Nui, is a perennial favourite of scholars and the media because of its numerous giant stone figures and supposed mysteries. Most of these enigmas — including the origins of the statues and the denuded landscape — have been solved in recent decades through painstaking work by archaeologists, anthropologists, environmentalists, linguists and geneticists.
A consensus view has emerged, summarized in Easter Island, Earth Island (Thames and Hudson; 1992) by botanist John Flenley and myself, that the island was deforested by its inhabitants. They cleared the land for crops and used timber for the transport and erection of ever more statues, with war the end result. In The Statues That Walked, archaeologists Terry Hunt and Carl Lipo present a different picture, portraying the islanders as environmentally sensitive and peace-loving until Europeans arrived in the eighteenth century. But some recent publications don't support their hypothesis.
Since the first known visit to the island by European vessels in 1722, people have wondered how so many huge stone statues could be transported and raised, given the lack of available timber. Discoveries of root moulds, pollen grains and stumps showed that the island was originally covered in millions of large palms and other tree species. Analyses of pollen and plant macrofossils revealed drastic deforestation between the thirteenth and seventeenth centuries, long before the Europeans arrived.
A wide range of evidence, along with oral traditions, suggest that the Easter Islanders had lived cooperatively for centuries after their arrival from Polynesia, probably in the early centuries AD. A thousand years later, they were in conflict, living in a barren landscape. The ecological decline of this small island serves as a warning of what is happening to Earth as a whole, as argued by Flenley and myself, and by geographer Jared Diamond in his best-seller Collapse (Viking, 2004).
Inevitably, this scenario has elicited doubts. Archaeologists Catherine and Michel Orliac have speculated that the island's deforestation was largely due to drought or climatic change, which may indeed have played a part. Others, including Hunt and Lipo, contend that the islanders' ills were caused by the arrival of Europeans, rather than internal social pressures.
In The Statues That Walked, Hunt and Lipo argue for a late date of around 1200 AD for the islanders' appearance on Rapa Nui. They claim that deforestation was mainly caused by the rats that came with them. Having found some palm nuts bearing gnaw-marks, they attribute the extinction of the island's big palm to rat predation, although they say little about other tree species. The statues, they posit, were moved upright for many miles by swivelling, which required little timber. And despite the deforestation, they say, the islanders continued to grow sufficient food and remain free of quarrels until Europeans brought violence, germs and eventual devastation.
The authors' new scenario does support the consensus view that the island was only colonized once, by Polynesians — and not, contrary to the theory of Norwegian adventurer Thor Heyerdahl, by Amerindians from the New World. The book contains good passages on the carving and transportation of the statues — which we know from oral testimony to be ancestor figures that were venerated by the islanders — including an account of the pioneering excavations of the statue roads by US geologist Charlie Love. The practice of lithic mulching, in which millions of stones are spread over the soil to retain moisture for crops, is described in detail.
But coverage of work by others is incomplete. For instance, the authors mention only their own survey of the statues and not the decades-long (and ongoing) cataloguing by US archaeologist Jo Anne Van Tilburg. Nor do they note some recent published evidence that, in my view, refutes the book's basic tenets.
For example, a variety of evidence contradicts their claim of rat predation: numerous palm fruits not gnawed by rats, palm stumps burned and cut, continued germination of palms despite the rats' presence, and the disappearance of other plant species that coexist with rats elsewhere. Hunt and Lipo's claim that human skeletal remains show little evidence of lethal trauma is refuted by quotes from anthropologist Douglas Owsley, the author of a 1994 paper that they reference. After examining more than 600 Easter Island skeletons, Owsley stated in a 2003 BBC documentary that the extreme frequency of injuries proved that these were people at war: “They're slugging it out, there's no doubt about it.”
Hunt and Lipo present some of the island's many features entertainingly, but the history of Rapa Nui is more complex than they allow.
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Bahn, P. Anthropology: Head to head. Nature 476, 150–151 (2011). https://doi.org/10.1038/476150a