Thousands of years ago, in North America’s past, all of its megafauna—large mammals such as mammoths and giant bears—disappeared. One proposed explanation for this event is that when the first Americans migrated over from Asia, they hunted the megafauna to extinction. These people, known as the Clovis society after a site where their distinctive spear points were first found, would have been able to use this food source to expand their population and fill the continent rapidly. Yet many scientists argue against this “Pleistocene, the period between about 2.5 million and 11,700 years ago during which humans first appeared on Earth, overkill” hypothesis. Modern humans have certainly been capable of such drastic effects on animals, but could ancient people with little more than stone spears similarly have caused the extinction of numerous species of animals. Thirty-five genera or groups of species (and many individual species) suffered extinction in North America around 11,000 B.C., soon after the appearance and expansion of Paleo-Indians, a group of hunters active in America during the late Pleistocene, throughout the Americas (27 genera disappeared completely, and another 8 became locally extinct, surviving only outside North America).

Although the climate changed at the end of the Pleistocene, warming trends had happened before. A period of massive extinction of large mammals like that seen about 11,000 years ago had not occurred during the previous 400,000 years, despite these changes. The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals. Was this coincidence or cause-and-effect?

We do not know. Ecologist Paul S.Martin has championed the model that associates the extinction of large mammals at the end of the Pleistocene with human predation. With researcher J.E.Mosimann, he has co-authored a work in which a computer model showed that in around 300 years, given the right conditions, a small influx of hunters into eastern Beringia 12,000 years ago could have spread across North America in a wave and wiped out game animals to feed their burgeoning population.

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The researchers ran the model several ways, always beginning with a population of 100 humans in Edmonton, in Alberta, Canada, at 11,500 years ago. Assuming different initial North American big-game-animal populations (75–150 million animals) and different population growth rates for the human settlers (0.65%–3.5%), and varying kill rates, Mosimann and Martin derived figures of between 279 and 1,157 years from initial contact to big-game extinction.

Many scholars continue to support this scenario. For example, geologist Larry Agenbroad has mapped the locations of dated Clovis sites alongside the distribution of dated sites where the remains of wooly mammoths have been found in both archaeological and purely paleontological contexts. These distributions show remarkable synchronicity (occurrence at the same time).

There are, however, many problems with this model. Significantly, though a few sites are quite impressive, there really is very little archaeological evidence to support it. Writing in 1982, Martin himself admitted the paucity of evidence; for example, at that point, the remains of only 38 individual mammoths had been found at Clovis sites. In the years since, few additional mammoths have been added to the list; there are still fewer than 20 Clovis sites where the remains of one or more mammoths have been recovered, a minuscule proportion of the millions that necessarily would have had to have been slaughtered within the overkill scenario.

Though Martin claims the lack of evidence actually supports his model—the evidence is sparse because the spread of humans and the extinction of animals occurred so quickly—this argument seems weak. And how could we ever disprove it. As archaeologist Donald Grayson points out, in other cases where extinction resulted from the quick spread of human hunters—for example, the extinction of the moa, the large flightless bird of New Zealand—archaeological evidence in the form of remains is abundant. Grayson has also shown that the evidence is not so clear that all or even most of the large herbivores in late Pleistocene America became extinct after the appearance of Clovis. Of the 35 extinct genera, only 8 can be confidently assigned an extinction date of between 12,000 and 10,000 years ago. Many of the older genera, Grayson argues, may have succumbed before 12,000 B.C., at least half a century before the Clovis showed up in the American West.

1.The word “proposed” in the passage is closest in meaning to 题型分类：词汇题

A.accepted

B.obviousC.

debatable

D.suggested

选项分析：原句为这件事的一个 proposed 解释。D选项 suggested“被提议的”，与 proposed“被提议的；被建议的”意义相似，且符合语境。

A选项 accepted：可接受的；

B选项 obvious：明显的；

C选项 debatable：可争论的。

Question 2 of 14

2.The word “distinctive” in the passage is closest in meaning to 词汇题

A.hidden

B.characteristic

C.scattered

D.rare

选项分析：The Clovis society 因为在这个地点发现矛尖而被命名，可以推测这些矛尖是很有特色的，即B选项 characteristic“特有的，表示特性的”。

C选项 scattered：分散的；

D选项 rare：稀有的。

3.Why does the author compare Modern humans with ancient people?修辞目的题

A.To argue that modern people have continued to have drastic effects on animal species

B.To illustrate how people from different historical times treated animals differently

C.To question the idea that ancient people could have hunted the megafauna to extinction

D.To emphasize that modern people are more successful hunters than ancient people were

题干分析：考察句子之间的关系；根据 Modern humans 和 ancient people 定位到第一段倒数第二句。

选项分析：定位句说“现代人类当然能够对动物产生如此剧烈的影响，但是仅仅拥有石矛的远古人类是否也同样导致了众多物种的灭绝呢?”这句说提到了古代技术不发达，可能无法造成灭绝，用于支持前一句观点，反对本文第一个观点“最初的美洲人使巨型动物灭绝”。即C选项。

A选项，continued to have drastic effects 无中生有。

B选项，treated animals 无中生有，前半句只说了能够造成大的影响，但没有说如何对待动物。

D选项，modern people are more successful hunters 无中生有，只说了现代人能造成影响，没有说因为他们是成功的猎人而造成影响。

4.In using the word “coincidence” in the passage, the author refers to events that occurred 词汇题

A.after a period of many years

B.subsequent to a prediction

C.from time to time

D.at the same time and by chance

选项分析：coincidence 表明前文提到的事情可能是“巧合，同时存在”，对应D选项。也可以根据 coincidence 与 cause-and-effect 意义一定不相同选择，不是“原因和结果”，那就是“by chance：偶然”，对应D选项。

A选项 after a period of many years：多年后；

B选项 subsequent to a prediction：预测后；

C选项 from time to time：不时。

5.According to paragraph 2, what suggests that human activity played a role in the extinction of mammals about 11,000 years ago?

A.Climate changes that would have favored human population expansion occurred at the time of the extinctions.

B.The presence of human hunters had caused animal extinctions in other time periods.

C.There was a pattern of climate change earlier than 11,000 years ago that had not caused animal extinctions.

D.Harmful climate changes 11,000 years ago would have required humans to hunt larger numbers of animals for food.

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 or leave out essential information. 简化句子题

A.A computer model was designed to determine how long it would have taken for a small group of hunters to spread across North America.

B.A computer model showed that it was possible for a small group of hunters to spread across North America and kill off game animals in just 300 years.

C.According to a computer model, people coming into North America 12,000 years ago had to kill game animals in order to feed their population.

D.According to a computer model, about 12,000 years ago conditions enabled a small group of hunters to enter and cross North America in about 300 years.

原文分析：简化题考察找主干和逻辑的能力，原文为“与研究员合作的电脑模型显示，在大约300年的时间内，在合适的条件下，12000年前一小群猎人流入东部波尼吉亚就可能席卷北美并消灭动物来喂养迅速增长的人口”。 本句的重要信息在后半部分模型显示了什么。

选项分析：B选项 a small group of hunters 对应原句 a small influx of hunters；wiped out 对应原句 kill off，“计算机模型显示，一小群猎人可能在仅仅300年的时间里，分散在北美地区并消灭动物”。与原句重要意思相符。

A选项，determine how long 无中生有，模型只演示了一个时间。

C选项，had to kill game animals 不是本句重点，原句用的是 wiped out game animals 来显示使动物很快灭绝。并且缺乏句子主干信息 spread across North America。

D选项，缺少句子主干信息 wiped out game animals。

7.Which of the following best describes the results of the research discussed in paragraph 4?

A.Scientists used mathematical models to show that most of the extinctions occurred in areas where humans had recently arrived.

B.Scientists established that the main population of North Americans who hunted lived in Canada during the time of the megafauna extinctions.

C.Scientists used numerical models to confirm that a small population of humans could have caused big-game extinctions in a relatively short period of time.

D.Scientists used statistics to prove beyond doubt the currently accepted view that human hunters were the main cause of the megafauna extinctions.

题型分类：事实信息题

原文定位：根据 the results of the research 定位到最后一句。

最后一句的结论是人类最初接触大型生物到其灭绝是在279年到1157年之间。C选项 a small population 对应第一句 a population of 100 humans，big-game extinctions 对应最后一句 big-game extinction，a relatively short period of time 对应最后一句 between 279 and 1,157 years。

A选项，where humans had recently arrived 无中生有，第四段只讨论了初始100人的情况。

B选项，the main population…lived in Canada 无中生有。

D选项，the main cause of the megafauna extinctions 过于极端，只讨论了人类会导致灭绝，但没有说人类是主要原因。

8.Which of the following statements about Larry Agenbroad’s work is implied in the discussion in paragraph 5?推论题

A.Agenbroad showed that Mosimann and Martin’s estimates of the amount of time needed to drive big-game to extinction were correct.

B.Agenbroad’s maps were the first to indicate the ages of the Clovis sites.

C.Agenbroad reinforced the idea that humans could have caused the extinctions.

D.Agenbroad’s studies of wooly mammoths led to his discovery of Clovis sites.

Paragraph 5 is marked with an arrow

我的答案：A

正确答案：C

题型分类：推论题

原文定位：根据 Larry Agenbroad 定位到第二句。

选项分析：定位句是一个例子：“LA 绘制了不同时期克洛维斯遗址的位置，以及不同时期猛犸象遗体的分布。这些分布显示出明显的同步性”。例子一般用于前文观点的解释，而C选项 reinforced the idea 对应第一句 continue to support，the idea that humans could have caused the extinctions 对应第一句 the idea that humans could have caused the extinctions。

A选项，the amount of time 无中生有，第五段没有提279 到1157年。

B选项，the first to 过于极端，文中没有提示是第一个。

D选项，led to“导致”，逻辑关系错误，两者没有因果关系。

9.The word “admitted” in the passage is closest in meaning to 词汇题

A.accepted the truth of

B.was unaware of

C.was troubled by

D.called attention to

我的答案：A

正确答案：A

选项分析：原句为 Martin 自己 admitted 证据的贫乏，推测 admitted 意为“承认”，与A选项 accepted the truth of“接受，承认”意义相近。

B选项 was unaware of：未察觉到……；

C选项 was troubled by：被……困扰；

D选项 called attention to：呼吁注意……。

10.According to paragraph 6, which of the following statements challenges the view that hunting by humans caused the extinctions of North American megafauna?事实信息题

A.The Clovis sites that contain the remains of mammoths were settled by humans long after the extinctions occurred.

B.Only a few of the Clovis sites are located near known mammoth habitats.

C.No archaeological evidence of extinctions has been found at Clovis sites since 1982.

D.The number of mammoth remains found at Clovis sites is smaller than would be expected if hunting by humans had caused the extinctions.

Paragraph 6 is marked with an arrow

我的答案：D

正确答案：D

原文定位：第六段都在讲 challenges the view。选项中的 Clovis sites 出自最后两句。

选项分析：文章倒数第二句举例说在 Clovis sites 只有38具猛犸象遗体。倒数第一句说少于20个 Clovis sites 有猛犸象遗体被发现，是一个很小的比例在过度捕杀假设中几百万一定被宰杀的猛犸象中。这两句说明应该有更多的遗体被发现。D选项 smaller than would be expected 对应原文最后一句 a minuscule proportion of the millions that necessarily would have had to have been slaughtered。hunting by humans had caused the extinctions 对应最后一句 the overkill scenario。

A选项 long after the extinctions occurred 无中生有。

B选项 near known mammoth habitats 无中生有。

C选项 No archaeological evidence 与原文倒数第一句 In the years since, few additional mammoths have been added to the list 矛盾。

11.In paragraph 7, why does the author mention that there is abundant archaeological evidence for the extinction of the New Zealand moa? 修辞目的题

A.To show that extinctions occurred in areas other than North America

B.To challenge Martin’s claim that the lack of megafauna remains supports his model of the megafauna extinctions

C.To identify a country where humans were highly skilled as hunters

D.To help explain why it is unclear whether all large herbivores of late Pleistocene America became extinct after the appearance of Clovis

题干分析：考察句子之间的关系。由 New Zealand 定位到文章第三句。

选项分析：新西兰出现在一个例子中，例子一般用于前文观点，即第二句中的“And how could we ever disprove it?”。it 对应B选项的 Martin’s claim，disprove 对应B选项的 challenge。

A选项，这个例子不是要支持动物灭绝发生了。

C选项，highly skilled as hunters 无中生有。

D选项内容出自下一句，这一句引出了新的观点与前文的例子无关。

Question 12 of 14

Paragraph 7 suggests that Donald Grayson believes which of the following about the remains at Clovis sites and megafaunal extinctions? 事实信息题

A.The rapid rate of the spread of humans explains why the extinctions also occurred at a rapid rate.

B.The lack of evidence of human-caused extinctions is not surprising in view of the speed with which the extinctions occurred.

C.It is likely that more evidence will be found as dating methods improve.

D.If humans did contribute to the extinctions, much more evidence of that would have been found by now.

Paragraph 7 is marked with an arrow

我的答案：B

正确答案：D

选项分析：第七段第一句先说了 Martin 给缺乏证据提出了一个说法，第二句和第三句 Donald Grayson 说其他地方人类导致的物种灭绝留下了大量的证据，来反驳 Martin 的说法。两句综合为D选项，much more evidence of that would have been found 对应第三句 abundant。

A选项出自第一句，是 Martin 的解释，与 Donald Grayson 无关，并且 explains why the extinctions also occurred at a rapid rate 无中生有。

B选项出自第一句，与 Donald Grayson 无关。

C选项 more evidence will be found 无中生有。

13.Look at the four squares [■] that indicate where the following sentence could be added to the passage.插入句子题

One possible nonhuman cause—weather cycles—is not consistent with what scientists know about the timing of the extinctions.

Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.

我的答案：A

正确答案：A

题干分析：考察句子和句子之间的衔接判断（通过 weather cycles 和 the timing of the extinctions 可以预测后面有可能会讲到气候周期和动物灭绝的时间）。待插入句“一种可能的非人类原因—气候周期—与科学家所知的物种灭绝的时间并不一致”。

选项分析：A选项后面两句分别提到了气候周期以及灭绝时间，符合插入句内容。

B选项后面一句只说了灭绝时间没有说气候周期，不符合插入句内容。

C选项，插入句没有代词，是一个引出话题句，而不是总结句，所以不应该放在第三句的位置。

D选项后一句有“this coincidence”代词和前一句呼应，此处不能插入句子。

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 sentences 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.文章总结题

About 11,000 years ago, all of North America’s megafauna became extinct.

Answer Choices:

A.That the first humans migrated to North America near the same time as the extinctions of the megafauna has led many to believe that hunting by humans was a significant cause of those extinctions.

B.Early North Americans known as the Clovis society developed spears in order to hunt enough large animals to feed their population as it expanded across vast areas of the continent.

C.Support for the hypothesis that hunting by humans caused the extinctions has been provided by computer models, as well as by the discovery of some mammoths’ remains near human settlements.

D.Scientists have proven that the human hunters of large animals who migrated across North America grew in number so quickly that they killed off most of the megafauna within a few hundred years.

E.There is more evidence that human settlers hunted large flightless birds like the moa into extinction than there is that hunters caused the extinction of large mammals like the mammoth.

F.Some scholars argue that the evidence linking mammoth remains to human settlements is insufficient to establish that hunting by humans was a significant factor in the megafauna extinctions.

我的答案：BCD

正确答案：ACF

题干分析：选择概括性的正确选项。

选项分析：A选项为第一段和第二段重要信息。hunting by humans was a significant cause of those extinctions 对应第一段第二句 the first Americans migrated over from Asia, they hunted the megafauna to extinction。near the same time as the extinctions of the megafauna 对应第二段倒数第二句 The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals。

C选项为第三、四、五段重要信息。provided by computer models 对应第三段第一句 championed the model that associates the extinction of large mammals at the end of the Pleistocene with human predation。the discovery of some mammoths’ remains near human settlements 对应第五段第二句。

F 选项为第六段重要信息。the evidence linking mammoth remains to human settlements is insufficient 对应第六段第二句 there really is very little archaeological evidence to support it。

B选项错误，信息与第一段有关，但是 developed spears in order to hunt enough large animals 无中生有。

D选项错误，Scientists have proven that 过于极端，第一段说的是 One proposed explanation，后文也提出了其他对这个说法的质疑。

E 选项错误，信息出自第七段，但只在第三句提到，是一个细节论据，不是中心观点。

关键词： 无中生有 倒数第一