It has long been accepted that the Americas were colonized by a migration of peoples from Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between northeastern Asia and Alaska) during the last Ice Age. The first water craft theory about this migration was that around 11,000-12,000 years ago there was an ice-free corridor stretching from eastern Beringia to the areas of North America south of the great northern glaciers. It was this midcontinental corridor between two massive ice sheets–the Laurentide to the east and the Cordilleran to the west–that enabled the southward migration. But belief in this ice-free corridor began to crumble when paleoecologist Glen MacDonald demonstrated that some of the most important radiocarbon dates used to support the existence of an ice-free corridor were incorrect. He persuasively argued that such an ice-free corridor did not exist until much later, when the continental ice began its final retreat.
Support is growing for the alternative theory that people using watercraft, possibly skin boats, moved southward from Beringia along the Gulf of Alaska and then southward along the Northwest coast of North America possibly as early as 16,000 years ago. This route would have enabled humans to enter southern areas of the Americas prior to the melting of the continental glaciers. Until the early 1970s,most archaeologists did not consider the coast a possible migration route into the Americas because geologists originally believed that during the last Ice Age the entire Northwest Coast was covered by glacial ice. It had been assumed that the ice extended westward from the Alaskan/Canadian mountains to the very edge of the continental shelf, the flat, submerged part of the continent that extends into the ocean. This would have created a barrier of ice extending from the Alaska Peninsula, through the Gulf of Alaska and southward along the Northwest Coast of north America to what is today the state of Washington.
The most influential proponent of the coastal migration route has been Canadian archaeologist Knut Fladmark. He theorized that with the use of watercraft, people gradually colonized unglaciated refuges and areas along the continental shelf exposed by the lower sea level. Fladmark’s hypothesis received additional support form from the fact that the greatest diversity in native American languages occurs along the west coast of the Americas, suggesting that this region has been settled the longest.
More recent geologic studies documented deglaciation and the existence of ice-free areas throughout major coastal areas of British Columbia, Canada, by 13,000 years ago. Research now indicates that sizable areas of southeastern Alaska along the inner continental shelf were not covered by ice toward the end of the last Ice Age. One study suggests that except for a 250-mile coastal area between southwestern British Columbia and Washington State, the Northwest Coast of North America was largely free of ice by approximately 16,000 years ago. Vast areas along the coast may have been deglaciated beginning around 16,000 years ago, possibly providing a coastal corridor for the movement of plants, animals, and humans sometime between 13,000 and 14,000 years ago.
The coastal hypothesis has gained increasing support in recent years because the remains of large land animals, such as caribou and brown bears, have been found in southeastern Alaska dating between 10,000 and 12,500 years ago. This is the time period in which most scientists formerly believed the area to be inhospitable for humans. It has been suggested that if the environment were capable of supporting breeding populations of bears, there would have been enough food resources to support humans. Fladmark and other believe that the first human colonization of America occurred by boat along the Northwest Coast during the very late Ice Age, possibly as early as 14,000 years ago. The most recent geologic evidence indicates that it may have been possible for people to colonize ice-free regions along the continental shelf that were still exposed by the lower sea level between13,000 and 14,000 years ago.
The coastal hypothesis suggests an economy based on marine mammal hunting, saltwater fishing, shellfish gathering, and the use of watercraft. Because of the barrier of ice to the east, the Pacific Ocean to the west, and populated areas to the north, there may have been a greater impetus for people to move in a southerly direction.
Paragraph 1: It has long been accepted that the Americas were colonized by a migration of peoples from Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between northeastern Asia and Alaska) during the last Ice Age. The first water craft theory about this migration was that around 11,000-12,000 years ago there was an ice-free corridor stretching from eastern Beringia to the areas of North America south of the great northern glaciers. It was this midcontinental corridor between two massive ice sheets–the Laurentide to the east and the Cordilleran to the west–that enabled the southward migration. But belief in this ice-free corridor began to crumble when paleoecologist Glen MacDonald demonstrated that some of the most important radiocarbon dates used to support the existence of an ice-free corridor were incorrect. He persuasively argued that such an ice-free corridor did not exist until much later, when the continental ice began its final retreat.
1. According to paragraph 1, the theory that people first migrated to the Americans by way of an ice-free corridor was seriously called into question by
○paleoecologist Glen MacDonald's argument that the original migration occurred much later than had previously been believed
○the demonstration that certain previously accepted radiocarbon dates were incorrect
○evidence that the continental ice began its final retreat much later than had previously been believed
○research showing that the ice-free corridor was not as long lasting as had been widely assumed
2. The word “persuasively” in the passage is closest in meaning to
○aggressively
○inflexibly
○convincingly
○carefully
Paragraph 2: Support is growing for the alternative theory that people using watercraft, possibly skin boats, moved southward from Beringia along the Gulf of Alaska and then southward along the Northwest coast of North America possibly as early as 16,000 years ago. This route would have enabled humans to enter southern areas of the Americas prior to the melting of the continental glaciers. Until the early 1970s,most archaeologists did not consider the coast a possible migration route into the Americas because geologists originally believed that during the last Ice Age the entire Northwest Coast was covered by glacial ice. It had been assumed that the ice extended westward from the Alaskan/Canadian mountains to the very edge of the continental shelf, the flat, submerged part of the continent that extends into the ocean. This would have created a barrier of ice extending from the Alaska Peninsula, through the Gulf of Alaska and southward along the Northwest Coast of north America to what is today the state of Washington.
3. Paragraph 2 begins by presenting a theory and then goes on to
○ discuss why the theory was rapidly accepted but then rejected
○ present the evidence on which the theory was based
○ cite evidence that now shows that the theory is incorrect
○ explain why the theory was not initially considered plausible
4. The phrase “prior to” is closest in meaning to
○ before
○ immediately after
○ during
○ in spite of
5. Paragraph 2 supports the idea that, before the 1970s, most archaeologists held which of the following views about the earliest people to reach the Americas?
○They could not have sailed directly from Beringia to Alaska and then southward because, it was thought, glacial ice covered the entire coastal region.
○They were not aware that the climate would continue to become milder.
○They would have had no interest in migrating southward from Beringia until after the continental glaciers had begun to melt.
○They lacked the navigational skills and appropriate boats needed long-distance trips.
Paragraph 3: The most influential proponent of the coastal migration route has been Canadian archaeologist Knut Fladmark. He theorized that with the use of watercraft, people gradually colonized unglaciated refuges and areas along the continental shelf exposed by the lower sea level. Fladmark’s hypothesis received additional support form from the fact that the greatest diversity in native American languages occurs along the west coast of the Americas, suggesting that this region has been settled the longest.
6. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways to leave out essential information.
○Because this region has been settled the longest, it also displays the greatest diversity in Native American languages.
○Fladmark's hypothesis states that the west coast of the Americas has been settled longer than any other region.
○The fact that the greatest diversity of Native American languages occurs along the west coast of the Americans lends strength to Fradmark's hypothesis.
○According to Fladmark, Native American languages have survived the longest along the west coast of the Americas.
Paragraph 4: More recent geologic studies documented deglaciation and the existence of ice-free areas throughout major coastal areas of British Columbia, Canada, by 13,000 years ago. Research now indicates that sizable areas of southeastern Alaska along the inner continental shelf were not covered by ice toward the end of the last Ice Age. One study suggests that except for a 250-mile coastal area between southwestern British Columbia and Washington State, the Northwest Coast of North America was largely free of ice by approximately 16,000 years ago. Vast areas along the coast may have been deglaciated beginning around 16,000 years ago, possibly providing a coastal corridor for the movement of plants, animals, and humans sometime between 13,000 and 14,000 years ago.
7. The author's purpose in paragraph 4 is to
○ indicate that a number of recent geologic studies seem to provide support for the coastal hypothesis
○ indicate that coastal and inland migrations may have happened simultaneously
○ explain why humans may have reached America's northwest coast before animals and plants did
○ show that the coastal hypothesis may explain how people first reached Alaska but it cannot explain how people reached areas like modern British Columbia and Washington State
8. The word “Vast” in the passage is closest in meaning to
○Frozen
○Various
○Isolated
○Huge
Paragraph 5: The coastal hypothesis has gained increasing support in recent years because the remains of large land animals, such as caribou and brown bears, have been found in southeastern Alaska dating between 10,000 and 12,500 years ago. This is the time period in which most scientists formerly believed the area to be inhospitable for humans. It has been suggested that if the environment were capable of supporting breeding populations of bears, there would have been enough food resources to support humans. Fladmark and other believe that the first human colonization of America occurred by boat along the Northwest Coast during the very late Ice Age, possibly as early as 14,000 years ago. The most recent geologic evidence indicates that it may have been possible for people to colonize ice-free regions along the continental shelf that were still exposed by the lower sea level between13,000 and 14,000 years ago.
9. According to paragraph 5, the discovery of the remains of large land animals supports the coastal hypothesis by providing evidence that
○ humans were changing their hunting techniques to adapt to coastal rather than inland environments
○ animals had migrated from the inland to the coasts, an indication that a midcontinental ice-free corridor was actually implausible
○ humans probably would have been able to find enough resources along the coastal corridor
○ the continental shelf was still exposed by lower sea levels during the period when the southward migration of people began
10. The word “inhospitable”in the passage is closest in meaning to
○ not familiar
○ not suitable
○ not dangerous
○ not reachable
11. According to paragraph 5, the most recent geologic research provides support for a first colonization of America dating as far back as
○16,000 years ago
○14,000 years ago
○12,500 years ago
○10,000 years ago
Paragraph 6: The coastal hypothesis suggests an economy based on marine mammal hunting, saltwater fishing gathering, and the use of watercraft. Because of the barrier of ice to the east, the Pacific Ocean to the west, and populated areas to the north, there may have been a greater impetus for people to move in a southerly direction.
12. The word “impetus” in the passage is closest in meaning to
○ chance
○ protection
○ possibility
○ incentive
Paragraph 1: It has long been accepted that the Americas were colonized by a migration of peoples from Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between northeastern Asia and Alaska) during the last Ice Age. ■The first water craft theory about the migration was that around 11,000-12,000 years ago there was an ice-free corridor stretching from eastern Beringia to the areas of North America south of the great northern glaciers. It was the midcontinental corridor between two massive ice sheets-the Laurentide to the west-that enabled the southward migration. ■But belief in this ice-free corridor began to crumble when paleoecologist Glen MacDonald demonstrated that some of the most important radiocarbon dates used to support the existence of an ice-free corridor were incorrect. ■He persuasively argued that such an ice-free corridor did not exist until much later, when the continental ice began its final retreat. ■
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage.
Moreover, other evidence suggests that even if an ice-free corridor did exist, it would have lacked the resources needed for human colonization.
Where could the sentence best fit?
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Recent evidence favors a rival to the long-standing theory that the Americas were colonized 11,000-12,000 years ago by people migrating south from Beringia along a midcontinental ice-free corridor.
●
●
●
Answer Choices
○Evidence that an ice-free corridor between two ice sheets developed when the continental ice first began to melt came primarily from radiocarbon dating.
○There is growing support for the theory that migration took place much earlier, by sea, following a coastal route along Alaska and down the northwest coast.
○Recent geologic evidence indicates that contrary to what had been believed, substantial areas along the coast were free of ice as early as 16,000 years ago.
○Research now indicates that the parts of the inner continental shelf that remained covered with ice were colonized by a variety of early human groups well adapted to living in extremely cold environments.
○There is evidence suggesting that areas along the coast may have contained enough food resources between 13,000 and 14,000 years ago to have made human colonization possible.
○Even though the northern part of the continent allowed for a more varied economy, several early human groups quickly moved south.
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参考答案：
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4. ○1
5. ○1
6. ○3
7. ○1
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14. There is growing support…
Recent geologic evidence…
There is evidence suggesting…
美国西北海岸的移民
这种观念被人们接受很长时间了：美洲被一群来自亚洲的移民殖民统治着，他们在上一个冰河时代缓慢地跨越了一个叫做白令的大陆桥（现在白令海峡位于东北亚和阿拉斯加之间）。关于这些迁徙的第一个水路理论表明，大概在11 000到12 000年前，有一个不冻的走廊，它从白令海峡东部延伸到北美（大北部冰河的南部），是连在两个巨大冰床间的半大陆性走廊，向西的Laurentide使往南的迁移成为可能。但是当古生态学者Glen MacDonald证明一些用来支持不冻走廊存在的重要放射性碳时间不正确时，对于不冻走廊的信念就被粉碎了。他令人信服地主张那样的不冻走廊直到很久以后才出现，那时大陆冰开始最后的消退。
另外一种理论得到越来越多的人的支持，它认为可能早在16 000年前，人们使用船只，也许是那种兽皮做的小船，从白令沿着阿拉斯加海湾，然后沿着北美的西北海岸前进。这条路线使人类可以在大陆冰河解冻之前进入美洲南部地区。直到20世纪70年代早期，大部分考古学家都不认为海岸可能是进入美洲的移民路线，因为地理学家一开始就坚信整个西北海岸在上个冰河时代是被冰川覆盖的。人们猜测冰从阿拉斯加、加拿大山脉向西延伸到大陆架的边界，也就是大陆延伸到海洋中而被淹没的部分。这样就形成了一个由冰构成的，从阿拉斯加半岛，经过阿拉斯加海湾，向南沿着北美洲西北海岸延伸至今天的华盛顿州的冰层障碍。
海岸移民路线的最有影响力的支持者是加拿大考古学家Knut Fladmark。他认为通过船只的使用，人们逐渐殖民到没有冰冻的地方以及沿着大陆架的、由于海平面较低而裸露出来的地区。Fladmark的假设从一个事实那得到了更多的支持，因为美国本土语言的最大多样性出现在西海岸沿岸，这就表明这个地区是人类定居时间最早的。
更多最近的地质研究证明了13 000年前在加拿大的不列颠可伦比亚省主要海岸地区无冰区域的存在和结冰。现在研究表明，直到上个冰河时代末期，阿拉斯加东南、沿大陆架内的大部分地区并没有被冰层覆盖。一项研究表明，除了在不列颠哥伦比亚省东南部和华盛顿州之间的250英里的海岸地区以外，北美的西北海岸在大概16 000年之前都是没有冰的。沿海的辽阔地区的冰川在大约16 000年前开始融化，这就为13 000前到14 000年前的某一段时间内植物、动物和人类的迁移提供了一个海岸走廊。
海岸走廊假设近些年得到了越来越多的支持，因为一些大型动物（比如北美驯鹿、棕熊）的遗迹出现在阿拉斯加东南部地区，其时间为10 000年到12 500年之前。之前大部分科学家认为此时此地不适合人类生存。如果一种环境能满足熊的繁殖，那么它就有足够的食物来源来供应人类的生存。Fladmark和其他科学家都认为人类第一次乘船沿着西北岸到达美洲发生在冰河时代的晚期，可能早达14 000年以前。最新的地质资料表明：13 000年至 14 000年前，人们殖民因低海平面而裸露的大陆架沿岸的无冰区域是可能的。
海岸假设提出了一个以捕食海洋哺乳动物、捕捞咸水鱼类、使用船只为基础的自然经济。由于东部是冰障，西部是太平洋，北部是移民区，所以有一股强大的力量促使人们往南方迁移。
