GWD23另一道逻辑题求教

adasuying2004

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.

答案是D，楼主选B。偶承认熬太久伤不起啊。。脑子完全短路了。。

pennybehappy

up up

pennybehappy

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？

sdcar2010

it was proved that an ice-free corridor allowed passage south from the Alaska-Siberia land bridge at least 11,400 years ago

It was proved that a corridor ALLOWED PASSAGE at least 11,400 years ago.

passage = migration

通

colasama

我也选D

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.

-- by 会员 sdcar2010 (2011/6/12 10:51:47)

您说的两点换成老路一样说得通，第二点我的确说的不严谨，应该改为"起码缩短为18000-11400年前,有可能更短"


我这么想是因为
我觉得Using new radiocarbon dating techniques，能够修正的是对冰封时期的估计，而不是用这个技术来发现新路...
只要被冰封过的我都认为是老路~~


呵呵~~反正都是说有没办法去南方~~这个不影响做题，大家随意吧

colasama

我也看了10来分钟才完全搞明白。
完整解释：在Alaska南边发现木炭（人类居住痕迹），这木炭是11,200年前的。也就是那时候就已经有人在Alaska南边。

但是从Alaska向南迁移的路子在  18000年前---11000年前 这段时间是不通的，所以既然11,200年前南边就有人，他们只能是18000年前就已经过去（不然错过这个时间，只能等到11，000年前之后才能迁移，跟木炭年龄矛盾）

D告诉你，他们有可能在11，400年前才迁移的。weaken了18000年前就迁移了的结论。

sdcar2010

我也选D

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.

colasama

我也选D

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 不通的时间起码缩短为18,000 and 11,400，有可能更短

sdcar2010

The necessary assumption the research had was: There is no way to migrate south via the land bridge duing a certain time due to glacier.

D) says the above assumption is wrong. There is another passage, thus, weaken the conclusion.

Casting doubt on a necessary assumption an argument requires is one way to weaken that argument.