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?
Q30: GWD-11-Q41: 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? A. Using new radiocarbon dating techniques, it was determined that the charcoal from the Colorado site was at least 11,400 years old. B. Another campsite was found in New Mexico with remains dated at 16,000 years old. C. 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. D. 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. E. 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.
但是我觉得D说的不是有另外一条new route。 而是同一条route,以前以为18,000 and 11,000 years 是不通的。 现在新技术发现,不通的时间缩短为18,000 and 11,400
-- by 会员 colasama (2011/6/12 10:46:12)
1) The new route is a corridor or a tiny road through an area which was thought to be blocked by ice. 2) The new route is not 不通的时间缩短为18,000 and 11,400, but 通的时间 was at least 11,400 years ago.
但是我觉得D说的不是有另外一条new route。 而是同一条route,以前以为18,000 and 11,000 years 是不通的。 现在新技术发现,不通的时间缩短为18,000 and 11,400
-- by 会员 colasama (2011/6/12 10:46:12)
1) The new route is a corridor passage, or a tiny road through an area which was thought to be blocked by ice. 2) The new route is not 不通的时间缩短为18,000 and 11,400, but 通的时间 was at least 11,400 years ago.
有一个疑问, 文中说了 glaciers prevented human migration south from the Alaska-Siberia land bridge between 18,000 and 11,000 years ago(都说了冰川阻挡了移民者) 而D说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(又说发现一条通道),这样算不算是反前提了?