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Topic 11
Reading
Around 1130 A.D., a group of highly intelligent and creative humans called the Anasazi from New Mexico’s Chaco Canyon vanished without a trace. Judging from available evidence, historians have suggested that the Anasazi’s disappearance was more likely to be caused by a severe summer drought.
First of all, the time when the Anasazi abandoned their villages coincided with the beginning of a sixty-year summer drought caused by global warming. During this time, uncommonly long heat waves swept across the world, making colder regions warmer and causing severe drought in the Americas. Scientists believe that the summer drought at Chaco Canyon was so severe that the Anasazi could not cope with it. In the end, they were forced to choose between starvation and migration.
Second, at Chaco Canyon, archeologists have discovered irrigation systems including diversion dams and canals directing water to the fields. The presence of these systems indicates that the Anasazi suffered shortages of water, and as a countermeasure for the crisis, they built irrigation systems to store water for drinking and growing crops. However, the drought caused by the global warming eventually may have been so overwhelming that it compelled the Anasazi to leave.
Finally, before the big summer drought, Chaco Canyon’s natural springs and fertile soil contributed to the tribe’s population growth. Perhaps, the tribe’s population had overgrown, and then the people were approaching the limit of local resources during the sixty-year summer drought. The subsequent food shortages forced this ancient people to migrate to a more habitable area. The fact that the Anasazi abruptly fled from their dwelling and left behind numerous artifacts suggests that they were displaced by a major natural disaster.
Topic 11
Listening
I think the evidence supporting the claim that the Anasazi disappeared because of severe drought is shaky.
First of all, there may have been a global warming in the past, and the subsequent droughts throughout the world affected different places, but the global warming did not affect areas where the Anasazi lived. The evidence suggests that some trees have existed at Chaco Canyon for thousands of years. If there had been a drought at Chaco Canyon, these trees would probably have died.
Second, the fact that irrigation systems such as dams and canals were found in planes where the Anasazi lived does not necessarily mean that this prehistoric tribe suffered severe droughts and abandoned their homeland as a result. On the contrary, the irrigation systems that existed for 150 years would indicate that the Anasazi were fully aware of their problems of water shortages and they somehow developed the technology to store water and divert it to grow corn, squash, and beans in a desert-like land. Scientists have found evidence that the Anasazi providently stored their crops against drought years, suggesting that this prehistoric people did not vanish because of a drought.
Finally, drought is only a hypothesis for the Anasazi’s disappearance. Recent findings by climatologists suggest that the great drought at Chaco Canyon was not severe enough to drive a nation of people to abandon their homes. The fact that the Anasazi abruptly left their homes might suggest they were attacked by another warring tribe rather than threatened by a drought. We should also consider other causes such as disease or overuse of farmland. In sum, the evidence so far is not enough to support the claim that the Anasazi vanished simply because of a severe drought.