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OFFICIAL54 Which of the following best describes the results of the research discussed in paragraph 4?

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Overkill of the North American Megafauna
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    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 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-lndians 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.

    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.

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

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【题目翻译】下列哪一项最能描述第4段所讨论的研究结果? A:科学家用数学模型表明,大多数物种灭绝发生在人类最近到达的地区。 B:科学家们证实,在大型动物灭绝期间,北美洲的主要狩猎者居住在加拿大。 C:科学家用数值模型来证实一小部分人可能在相对较短的时间内导致大型动物灭绝。 D:科学家利用统计数字毫无疑问地证明了目前公认的观点,即人类狩猎者是大型动物灭绝的主要原因。 【判断题型】题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】找到第四段中: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. 【逻辑分析】得出的数据结果是人类从最初开始接触到大型生物到其灭绝的这段时间是在279年到1157年之间。即一小部分人可能在相对较短的时间内导致大型动物灭绝。 【选项分析】 A:科学家们使用数学模型来表明大多数的灭绝发生在人类最近到达的地区,错误,原文没有提到是人类“最近到达”,所以排除。 B:科学家们确定,在巨型动物灭绝期间,狩猎的大部分北美人居住在加拿大,错误,原文只是说研究者拿加拿大的100人作为数据分析,并非推断历史事实。 C:科学家们使用数值模型来证实一小群人可能会在相对较短的时间内造成大猎物灭绝,选项中的“big-game”还有大猎物的意思,而这句话是最贴近选段的意义的,故为正确答案。 D:科学家利用统计数据来证明人类捕猎者是巨型动物灭绝的主要原因,这是毫无疑问的,理解错误,文中提到了关键的时间因素此处并没有说到,而这个模型也并不是用来证明人类是导致巨型动物灭绝的主要原因,故排除。

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