Under these conditions, he says, "Rats would reach a population of a few million within a couple of years." From there, time would take its toll. "Rats would have an initial impact, eating all of the seeds. With no new regeneration, as the trees die, deforestation can proceed slowly," he says, adding that people cutting down trees and burning them would have only added to the process. Eventually, the degeneration of trees, according to his theory, led to the downfall of the rats and eventually of the humans. The demise of the island, says Hunt, "was a synergy of impacts. But I think it is more rat than we think."
Hunt's findings caused a stir among Easter Island scientists. John Flenley, a pollen analyst at New Zealand's University of Massey, accepts that the numerous rats would have some impact on the island. "Whether they could have deforested the place," he says, "I'm not sure."
Flenley has taken core samples from several lakebeds formed in the island's volcanic craters. In these cores, he has found evidence of charcoal. "Certainly there was burning going on. Sometimes there was a lot of charcoal," he says. "I'm inclined to think that the people burning the vegetation was more destructive [than the rats]."
Adding to the civilization's demise, European explorers brought with them Western diseases like syphilis and smallpox. "I think that the collapse happened shortly before European discovery of the island," Flenley says. "But it could be that the collapse was more of a general affair than we think, and the Europeans had an effect on finishing it off."
Flenley, who initially surveyed Easter Island in 1977, was one of the first scientists to analyze the island's pollen—a key indicator of foresting. The island's volcanic craters, which once housed small lakes, were ideal sites for his research. "The sediment was undisturbed. Each layer was put down on top of the layer before," says Flenley, referring to core samples from one crater's lakebeds. "It's like a history book. You just have to learn to read the pages." The samples showed an abundance of pollen, indicating that the island had once been heavily forested. The pollen rate then dropped off dramatically. "When I dated the deforestation at that site, it came starting at about 800 A.D. and finishing at this particular site as early as 1000 A.D.," a finding in line with other radiocarbon dates on the island. Since this was one of the first settlement sites, Flenley says, it makes sense that deforestation would have occurred even earlier than it did on other parts of the island.
This crater, Flenley believes, would have been one of the only sources of freshwater on the island, and therefore one of the first places the Polynesians would have settled. "It wasn't only a site of freshwater, it was also a very sheltered crater," he says. "It would have been possible to grow tropical crops." Anakena, the beach where Hunt did his research, would have been a good place to keep their canoes and to go fishing, but not a good place to live. Hunt, Flenley says, "has definitely shown a minimum age for people being there, but the actual arrival of people could have been somewhat earlier."
Other scientists who work on the island also remain skeptical of Hunt's later colonization date of 1200 A.D. Jo Anne Van Tilburg, founder of the Easter Island Statue Project and a scientist at the University of California, Los Angeles, is one of the island's leading archaeologists and has studied the moai for nearly 30 years. "It's not logical that they were constructing megalithic sites within a few years of arrival on the island," she says. Van Tilburg and her colleagues have surveyed all 887 of the island's statues. "By 1200 A.D., they were certainly building platforms," she says referring to the stone walls on which the islanders perched the moai, "and others have described crop intensification at about the same time. It's hard for me to be convinced that his series of excavations can overturn all of this information."
Despite these questions, Hunt remains confident in his findings. Many scientists, he says, "get a date, tell a story, invest a lot in it, and then don't want to give it up. They had a very good environmental message."