Homo Sapien or Rattus Exulan?

By Richard Witting

The Island of Rapa Nui has long captured the interest and imagination of both the public and the scientific community. For the average person, the familiar big stone heads are awe-inspiring and iconic, and the island seems unimaginably remote. Scientists have puzzled over these heads: they are symbols of an ancient and now extinct culture, a culture that through some form of brilliant, primitive engineering feat was able to erect these massive monuments. Yet despite these impressive… erections… the ancient Rapa Nuians could not sustain their population’s needs and their society collapsed.  Or so the story goes… but is it true?

Collapse is hot…

Theories and ideas about the subject of collapse are an especially loved subject for scientists. Perhaps they are drawn to it out of a logical desire to avoid the mistakes that people in the past made that led to these collapses. Perhaps collapse resonates somewhere deep in all our psyche as a sort of meta fear of death; the complete death of our culture. In a paper by Joesphe Tainter titled Collapse, Sustainability, and the Environment: How Authors Choose to Fail or Succeed he reviews a selection of contemporary literature on the subject. First among these is the much read, and much despised, book by Jared Diamond titled Collapse: How Societies Choose to Fail or Succeed; in which Easter Island is first among his examples. Diamond holds up Easter Island as an example of the imminent destruction that we already suspect is threatening us: that manmade actions will cause a catastrophic collapse of the environment that sustains us—and that human decisions, for better or for worse, define these collapses. He proposes that, like the prehistoric Rapa Nuians,  this will be our undoing unless we act to change the outcome.

But what animal really caused Easter Island’s collapse?

Minus a handful of important traits (speech, upright walking, etc.) it is worth remembering that humans are also animals.  Much of human life is still driven by basic the necessities of food, shelter, and comforts. In pursuit of these needs we have been migrating around the earth for thousands of years, resituating ourselves in response to our world and environment.  When people from Polynesia first found their way to Easter Island, they found a fertile forested island thick with the palms which would sustain them for years, both as a primary food source and the key material for building deep water fishing boats. This forest was also home to 2000 species of now extinct birds — which constitutes a 20% decrease in the the species of birds known on the Earth (Steadman). As the classic narrative goes, the islanders then depleted all the resources of the island in pursuit of their unquenchable desire to build giant stone heads… or at least because the population grew beyond it’s carrying capacity. This led to a collapse of the island’s ecosystem and to the complete depletion of the soil’s fertility. The inhabitants turned to eating anything they could, and finally, to cannibalism.

Enter the rat…

A newer theory to the collapse of the Easter Island ecosystem concerns the introduction of the Polynesian rat, rattus exulans. This species was commonly brought by Polynesian voyagers to islands to serve as a food source. In examples from other islands the devastation of rats is well documented. The way this is done in a situation such as this is that the rats proliferate quickly and use the seeds of the palm tree as a food source. So much so that the palms become unable to repopulate themselves. In this scenario we see that the human decision to bring the rat to the island may have been the cause of the islands decline, not any failure by the people of the island to control their population growth, manage the islands resources or curb their head building enthusiasm.

or not…

While Diamond gives us as a species a huge amount of agency in our own self-destruction, Richardson Gill’s book The Great Maya Drought: Water, Life, and Death points out the vast complex array of forces in our world that are working against us such as drought, disease and ecological forces. Others also have pointed to possible non-human causes in the form of draught do to changing weather patterns may have been the cause of the decline. Gill’s also examines the appeal of collapse study and how it is interpreted. Obviously the current issues we face regarding climate change are real and need to be addressed but it should be done with caution and a close assessment of the implication of the idea. With collapse there is an implication of failure, that someone is to blame. Implied in the classic narrative of the collapse of Easter Island is the notion that the inhabitants were at fault somehow in their practices. For a moment it’s worth setting aside the truth of falsity of that narrative and instead to take a look at how that narrative might be used, by whom and for what.

Additionally this narrative leaves out the living descendants of those ancient people — who survived despite this collapse. Because they aren’t erecting large stone heads does that mean they are not currently a worthy people to know and study? Our concerns for understanding the past to predict the future means that we might overlook the present. How does a pursuit of these answers help those who inhabit the island now? What future do they face?

Flenley, John, and Paul Bahn

2003The Enigmas of Easter Island: Oxford University Press.

Mann, Daniel, et al.

2008Drought, vegetation change, and human history on Rapa Nui (Isla de Pascua, Easter Island). Quaternary Research 69(1):16-28.

Tainter, Joseph A.

2008Collapse, Sustainability, and the Environment: How Authors Choose to Fail or Succeed. Reviews in Anthropology 37(4):342-371.

Steadman, David W

1995 Prehistoric extinctions of Pacific island birds: biodiversity meets zooarchaeology. Science 267(5201):1123-1131.