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题库 / GMATLA-CR-39
Charcoal from a hearth site in Colorado, 2,000 miles south of Alaska, is known to be 11,200 years old. Researchers reasoned that, since glaciers prevented human migration south from the Alaska-Siberia land bridge between 18,000 and 11,000 years ago, humans must have come to the Americas more than 18,000 years ago.
Which of the following pieces of new evidence would cast doubt on the conclusion drawn above?
Using new radiocarbon dating techniques, it was determined that the charcoal from the Colorado site was at least 11,400 years old.
Another campsite was found in New Mexico with remains dated at 16,000 years old.
A computer simulation of glacial activity showed that it would already have been impossible for humans to travel south overland from Alaska 18,500 years ago.
Using new radiocarbon dating techniques, it was proved that an ice-free corridor allowed passage south from the Alaska-Siberia land bridge at least 11,400 years ago.
Studies of various other hunting-gathering populations showed convincingly that, once the glaciers allowed passage, humans could have migrated from Alaska to Colorado in about 20 years.
已知C地的木炭有11200年老，
冰川阻挡了人类在18000年前到11000年前迁徙→人类在18000年前就迁徙到了C
隐藏假设：有人才有木炭，木炭的年龄说明人类必须在那之前达到C地
D说明11400年前有通道让人类迁徙。
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