Monday, April 23, 2007

Colonization of Easter Island - and implications.

I have posted the poster that Terry Hunt and I plan to present at the Society for American Archaeology meetings in Austin, TX this week. You can download a pdf of the poster here. This poster presents an extended argument about the timing of the colonization of Easter Island (Rapa Nui). We suggest that the island was not occupied until about AD 1200, about 500 years after the "traditional" date of AD 700-900. While it might seem like a small point, this change in the chronology has rippling significance to the standard "collapse" story told by Flenley, Bahn, Diamond and others. What the date means is that there is only about 500 years for the entire prehistory of Easter Island - prior to Easter Sunday in AD 1722 when Roggeveen arrives on the island. 500 years for occupation, "climax," "collapse," and then rebound - if one is to accept the traditional story. One might think that this alone should present questions about the chronology as we present it. "If collapse occurred, then the short chronology can't be right." In fact, this is what a number of colleagues appear to believe and are arguing in print (Bahn and Flenley are publishing such a statement in the upcoming issue of Rapa Nui Journal). As it turns out, it appears that many researchers have worked backwards - while we have concrete evidence (as argued in the poster) for the "short" chronology, we don't have evidence for a "collapse" - at least pre-European arrival. This might seem odd to many as many assume that the story of collapse is one that is "obvious" or "certain." It's not. The problem here is a mixing of evidence and belief. This has resulted in what we term "belief based" archaeology for Easter Island. Researchers have made many claims about the prehistory of the islands but a remarkably large number of them are based on inferences derived from the story itself (i.e., circular reasoning). We do know without any reasonable doubt that there were large numbers of palm trees on the island prior to humans arriving. We also know at some point all of the trees went extinct. What we don’t know is the chronological and functional relations between humans and plants that resulted in the loss of trees. Lacking much of the basic evidence, a set of beliefs have been established and perpetuated that rationalize the story. For example: What is the connection between trees and people? Belief: Trees were used to move statues around (this is stated primarily because its assumed that this is why the trees went away) Evidence: We don’t know. We don’t even have evidence that the extinct palms were capable of moving statues around given that many of the related taxa have big mushy interiors. How did statues get moved? Belief: Trees used as levers or rollers Evidence: We don’t know but evidence points more towards the fact that they were “walked” rather than rolled. How many people were on the island in prehistory (at maximum)? Belief: 10-20,000 people because that’s the number assumed that were required for organizational structures to manipulate the movement of statues. Evidence: We don’t know though the number at contact is reported at 3-4,000 and the settlement patterns are largely dispersed rather than nucleated. When did people arrive on the island? Belief: 700-900AD because that is the amount of time it would take to get to 10-20,000 people Evidence: Looking critically at dates we can accept based on standard practices, we find that evidence points to 1200AD. This means that only 500 years passes before Europeans arrive (AD1722). When did the “collapse” occur? Belief: some several hundred years prior to European contact in AD1722. This gap is thought to occur to account for the well-fed and robust nature of the population in 1722 (i.e., post collapse) . Evidence: There is no evidence of prehistoric collapse. People were healthy in 1722, prior to that we simply don’t know but nothing exists to suggest cannibalism, warfare, catastrophe. Collapse certain did occur after 1722 – we have records of that (and was caused by disease and other dramatic population changes). How did people fight with one another? Belief: Obsidian bifaces called “mataa” are found all over the place. These were weapons. Evidence: The shape of the mataa are such that they would make terrible weapons. While there are few that are pointy, the vast majority are oddly shaped and have no pointed end. Their shape and usewear is consistent with cutting (if it were for stabbing one would expect significant impact damage on the tips – but that is not the case). Skeletal evidence also shows little evidence for traumatic injuries – skeletons exhibit non-lethal trauma.- How did people destroy their landscape? Belief: By cutting down the trees, the people “began a downward spiral” to cultural catastrophe – erosion and carrying capacity vanished. Evidence: Given known archaeological rat populations (we find them in all of the early layers) palm trees may not have been useful subsistence source – and may have harbored millions of rats. Polynesians who arrived on the island were cultivators – farmers – who relied on plants like the sweet potato, sugar cane, bananas. Thus its not clear there was a necessary relation between people and palm trees (other than the negative aspect of having them filled with rats eating the palm nuts). As for erosion – we know it occurred – but given the fact that the archaeological record is largely surficial over all (you can find mataa, obisidian flakes, groundstone every where) it doesn’t seem to have been prehistoric. Indeed, much of the major erosion seems to be a function of the 100 years of sheep ranching and other historic activities (most by Europeans). There are many more examples of a belief structure that focuses on "collapse" and "environmental overshoot" guiding what people perceive the evidence to be on Easter Island. All of these need to be carefully examined so that we can distinguish aspects of the archaeological record from the stories being spun about it.
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