LETTERS TO THE EDITORS
To the Editors:
We find it difficult to take seriously the article "Rethinking
the Fall of Easter Island" (September-October) in which Terry
L. Hunt concludes that rats, not humans, were the main cause of the
island's deforestation. We strongly believe that the archaeological
and botanical data do point clearly to a scenario of human
overexploitation of resources.
Dr. Hunt advocates the theory that colonists arrived relatively
late, around 1200 A.D. He supports this with carbon dating of
charcoal from a site called Anakena, where the base deposit is clay
soil with stratified sand on top. We assert that this finding is
weak: There is no "natural" stratified layer below the
lowest cultural one. How do we know that there were not other sandy
layers that blew or washed away before the ones Dr. Hunt
investigated were deposited? In addition, if this was the site of
the first settlement, why is there evidence that there were other
people at two other locations at the same date?
It seems likely that the charcoal Dr. Hunt identified was from the
palm tree Jubaea chilensis. This tree lives for about 2,000
years. There is only evidence that rats ate the fruits of the trees,
so if the rats did not arrive until 1200, and were mostly
responsible for deforestation, there should still be lots of palms left.
The date of deforestation based on pollen is not easily dismissed.
The deforestation at Rano Kau was shown by two dates to be virtually
complete by 1000. These dates were shown by sediment analysis to be
unlikely to be contaminated by inwashed older sediment.
Dr. Hunt also denies that any overpopulation-induced internal
warfare took place on Rapa Nui. There is abundant evidence that
obsidian spearheads proliferated after the deforestation, and there
is skeletal material that shows severe wounds.
We have not proved that there was ecological disaster, but we have
shown it could well have happened and in fact probably did so.
Palmerston North, New Zealand
Dr. Hunt responds:
Recent research from the Hawaiian Islands demonstrates that the
Pacific rat, carried by Polynesian colonists, exploded into the
millions and spread over the islands faster than people, consuming
seeds of native plants. In the absence of fire, felling or direct
human presence, rats deforested much of the Hawaiian Islands. Why
would their relative impact on Rapa Nui be any less?
The earliest human presence at Anakena is about 1200 A.D. We found
the oldest artifacts, charcoal and bones of introduced rats embedded
in the ancient soil horizon of the lowest clay layer. Directly
beneath these finds are palm root molds, proof of the layer's
undisturbed state. Our carbon dates also confirm a consistent
chronology of deposition from the bottom to the top of the sand
dune's layers. But nothing would stop early colonists from venturing
further from this site. Carbon dates contemporary (that is,
typically within 50 to 100 years) with those at Anakena would merely
reflect expansion across the island.
The question of the extinct palm's lifespan is relevant, but it is a
unique species or even distinct genus from the native palms growing
in Chile. Estimating its lifespan by comparison with different
species or genera is dubious. In any case, the equable climate of
Rapa Nui differs significantly from Chile's, raising doubts about
inferring growth rates or lifespan.
The claim of complete deforestation by 1000 A.D. is many centuries
earlier than the chronology established by multiple independent
research teams reporting more than 65 radiocarbon dates. These teams
detail a consistent chronology for deforestation that begins about
1250-1300 A.D., with signs of forest surviving into historic times.
Finally, some warfare may have taken place on Rapa Nui. But evidence
for it remains ambiguous. We have analyzed hundreds of the artifacts
Drs. Flenley and Bahn label "obsidian spearheads"
(mata'a), and only a minute fraction have anything
resembling a point. Studies of use-wear indicate these tools were
used in cutting and scraping plant materials. Published analysis of
hundreds of Rapa Nui skeletons has revealed that violent injury was
minimal, with signs of any fatal assaults even more rare.
Nowhere do I suggest that rats were the sole agent of deforestation
and Rapa Nui's downfall. I raise the question of their relative
impact. If the extinct palms of Rapa Nui did have a great lifespan,
felling and fire may have finished what rats started. Importantly,
these relative impacts have not yet been adequately researched.