Case Study Revisited: The Mystery of Easter Island
Most of what we know about Easter Island's past has been pieced together by archeologists and paleontologists. For example, the history of Easter Island's vegetation was established by examining pollen grains in layers of ancient sediments. Because the age of each sediment layer can be determined, and because each plant species can be identified by the unique appearance of its pollen, pollen analysis reveals how vegetation has changed over time.
The pollen record of Easter Island shows that, prior to human arrival, the island supported a diverse forest, including plants that could supply fiber for rope, and trees with long, straight trunks that would have been ideal for moving statues and making canoes. The forest, however, began to decline about 400 years after humans first settled on the island. By A.D. 1400, about a thousand years after the arrival of humans, almost all of Easter Island's tree species were extinct. A thousand years of clearing land for agriculture and cutting trees for firewood and construction material had destroyed the forest,
The destruction of the forest was paralleled by a corresponding wave of animal extinctions. Fossils show that Easter Island was once home to parrots, owls, herons, and numerous other bird species. At least 25 species of seabirds, including albatrosses, boobies, and frigate birds, once nested on the island. Today, Easter Island contains no native land birds or mammals. No animal larger than an insect is a permanent resident there.
Forest destruction no doubt hastened the disappearance of Easter Island's animals, but direct consumption by humans was also responsible. Archeologists investigating early sites of human settlement have found large quantities of bones from most of the extinct bird species in the sites' garbage heaps, evidence that the islanders made many meals of the local birds.
When the forest and its animals disappeared, the island's human population probably lacked adequate food. With no wood for canoes or boats, there was no way to leave the island. Ominously, garbage heaps from the post-forest period contain gnawed human bones, testimony to the cannibalism that emerged in this period. By the time Europeans arrived, the small number if people left on Easter Island lived impoverished lives and had no record of memory of the culture that built the magnificent statues.
What can we learn from Easter Island? According to the biologist and author Jared Diamond, "the meaning of Easter Island for us should be chillingly obvious. Easter Island is Earth writ small. Today, again, a rising population confronts shrinking resources. We too have no emigration valve, because all human societies are linked by international transport, and we can no more escape into space than the Easter Islanders could flee into the ocean. If we continue to follow our present course, we shall have exhausted the world's major fisheries, tropical rain forests, fossil fuels, and much of our soil by the time my sons reach my current age."
Answer the following questions about the timeline. Your instructor will tell you whether to write your answers in your book or to submit your answers online for electronic grading.
Objective
Step 2: Read "Case Study Revisited." Then study the incomplete timeline that follows the essay.