GWD-11-41

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?

1. Using new radiocarbon dating techniques, it was determined that the charcoal from the Colorado site was at least 11,400 years old.


2. Another campsite was found in New Mexico with remains dated at 16,000 years old.


3. 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.


4. 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.


5. 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.

Per Tianwan and Fair_sword, the answer is d.  

I don't really understand this question.  What is the relationship between the charcoal time (

11,200 years old) and the glazier-bridge time (glaciers prevented human migration south from the Alaska-Siberia land bridge between 18,000 and 11,000 years) ?  Maybe human use charcoal? Once charcoal appears, humen appear?

出现charcoal的地方暗示有人类出现过in Colorado；

结论是：人类在Colorado出现是在18000年前，前提是：11000到18000年间人类无法穿越A-S land bridge，因为galciers。削弱的方向：D－有一段没有ice，所以可以穿越。

Thanks, Stoneren!

Whenever I am online, I always see you!

此题我有疑问，　题目说　结论为１１０００－１８０００期间无人．ｄ　只是说可以通行的走廊存在于至少１１４００年前．那１１５００也是在１１４００年前２００００也是在１１４００年前，而后者就明显无法ｗｅａｋｅｎ作者的结论了

我选ｂ　发现有１１６００年的人类遗址存在，说明肯定在１１０００－１８０００期间有人过去了，完全绝对的反对了作者．

请大家指正．　谢谢

new mexcio is not relevant

B错并不是因为New Mexico无关。B想混淆大家的是：在11000和18000这段时间里，new mexico 也有人住。（因为new mexico 在 colorado的南面，ETS想误导大家16000年时有人通过Alaska-Siberia land bridge）

但B并不能weaken原推论。因为即使new mexico 16000有人住，这些人也可能是在18000之前就通过Alaska-Siberia land bridge 搬过来的。

又看了这个帖子，我觉得大家没有切中要害：（因为从这上面获益不少，所以把自己不成熟的想法提出了，表示我感激的诚意，实在无他。）

其实，这题的关键在于提问方式——下面的哪个新证据可以推翻结论？

感觉到提问方式的改变了没有？我原先没有看提问，读完文章后立刻抱着ets是“提问假设或者削弱论证”的想法作题，因此才中招的。

再说回来，如果ets提问改为“哪个是假设”或者“哪个削弱论证”，大家还会排除B吗？

所以我认为，有些人做这题是恰好蒙对的。因为出题者阴险地在选项设计上和提问方式上同时作了文章，这是我认为大家要小心的:原先的想法是论证与假设的评价必然是建立在原因和结论之间的，单独反对前提毫无意义，可是这题的关键是提问哪个新证据，就是说前提改变，因此可以选择现在的答案。

大家互相揭短，共同破解ETS啊！

前提改变则范畴大变！！！

数学公式都是有前提的有条件的，任何规则都是有前提才成立的。这是我从这个题做错得出的总结。

除非提问针对的是前提或者结论，假设题答案必然是前提与结论之间关系，仅仅针对其中一个没有意义。

答案：B

原文结论："humans must have come to the Americas more than 18,000 years ago."

The Americas (用google查的）
(sometimes referred to as America) is the area including the land mass located between the Pacific Ocean and the Atlantic Ocean, generally divided into North America and South America. The term also usually includes the Caribbean, the islands in and around the Caribbean Sea, and Greenland, though not Iceland, for cultural and historical reasons. The isthmus of Central America is usually considered geographically part of North America. The Americas are often also described collect...

所有人都应该知道new mexico是美洲大陆的一部分，在该处发现"remains dated at 16,000 years old"的证据，完全可以削弱原文结论。