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在上一次冰期的高峰，东北亚地区（西伯利亚）和阿拉斯加曾由一片广阔的陆地相连，这片土地被叫做白令陆桥。

During the peak of the last ice age, northeast Asia (Siberia) and Alaska were connected by a broad land mass called the Bering Land Bridge.

这个陆桥的存在是由于当时地球上大部分的水已经冻结成冰盖，所以当时的海平面比现在低100多米。

This land bridge existed because so much of Earth’s water was frozen in the great ice sheets that sea levels were over 100 meters lower than they are today.

在10000 到25000年之前，西伯利亚，白令陆桥和阿拉斯加拥有很多相同的环境特征。

Between 25,000 and 10,000 years ago, Siberia, the Bering Land Bridge, and Alaska shared many environmental characteristics.

这些共同特征包括：由大型哺乳动物组成的哺乳动物群落；由广袤的草原、狂风肆虐的沙丘和冻原组成的植物群；以及冬季寒冷干燥而夏季些许温暖的气候。

These included a common mammalian fauna of large mammals, a common flora composed of broad grasslands as well as wind-swept dunes and tundra, and a common climate with cold, dry winters and somewhat warmer summers.

白令海两岸很多现存的植物群和动物群落在许多方面都被认为是冰河时期地貌的残留。这一认知导致该地区被命名为白令陆桥。

The recognition that many aspects of the modern flora and fauna were present on both sides of the Bering Sea as remnants of the ice-age landscape led to this region being named Beringia.

正是通过白令陆桥，一些以大型哺乳动物为捕猎对象的猎人小团体逐渐扩大了自己的狩猎领地，并最终占领了北美和南美洲。

It is through Beringia that small groups of large mammal hunters, slowly expanding their hunting territories, eventually colonized North and South America.

在这一点上考古学家们是普遍认同的，但是他们的认同点也仅此而已。

On this archaeologists generally agree, but that is where the agreement stops.

解释美洲大陆上的人类居住情况是一个具有广泛争议的问题。这也是古生态学的研究范畴。但是想要了解人类历史，我们首先要知道：当时的白令陆桥是什么样的？

One broad area of disagreement in explaining the peopling of the Americas is the domain of paleoecologists, but it is critical to understanding human history: what was Beringia like?

曾经的白令地貌与现在大不相同。

The Beringian landscape was very different from what it is today.

狂风肆虐的广阔山谷、冰川覆盖的山脉、稀少的植被和较低的湿度使这片土地令人望而生畏。

Broad, windswept valleys; glaciated mountains; sparse vegetation; and less moisture created a rather forbidding land mass.

这个陆块上曾生存过成群的现已灭绝的猛犸象、野牛、马和接近现代版的驯鹿、麝牛、麋鹿和赛加羚羊。

This land mass supported herds of now-extinct species of mammoth, bison, and horse and somewhat modern versions of caribou, musk ox, elk, and saiga antelope.

这些食草动物又成为了巨型短面熊、剑齿猫和大型狮子等大型哺乳动物的食物来源。

These grazers supported in turn a number of impressive carnivores, including the giant short-faced bear, the saber-tooth cat, and a large species of lion.

哺乳动物群的存在需要依靠草地植被，因此，北极生物学家戴尔·古思莱认为，尽管这个地区寒冷干燥，但曾经肯定有广阔且茂密的植被覆盖，为成群的猛犸象、马和野牛提供了生存的保障。

The presence of mammal species that require grassland vegetation has led Arctic biologist Dale Guthrie to argue that while cold and dry, there must have been broad areas of dense vegetation to support herds of mammoth, horse, and bison.

不仅如此，几乎所有的冰期动物群落都有牙齿。这就证明它们已经适应了以禾草和莎草为食，而不是依靠苔藓和地衣等现代植物生存。

Further, nearly all of the ice-age fauna had teeth that indicate an adaptation to grasses and sedges; they could not have been supported by a modern flora of mosses and lichens.

古思莱还表明，当时的陆桥地区可能时常经历狂风的侵袭，尤其是在冬天。

Guthrie has also demonstrated that the landscape must have been subject to intense and continuous winds, especially in winter.

他通过对马和野牛的解剖印证了自己的论点。因为解剖中发现这些动物并没有在积雪覆盖的地面寻找食物的能力。

He makes this argument based on the anatomy of horse and bison, which do not have the ability to search for food through deep snow cover.

它们生活的地方需要有强风帮助它们扫除冬季的大雪，使得下面的干草能够显露出来。

They need landscapes with strong winds that remove the winter snows, exposing the dry grasses beneath.

古思莱用了“猛犸草原”这一术语描述了陆桥地区的特征。

Guthrie applied the term “mammoth steppe” to characterize this landscape.

然而，保罗·科林沃克提出了一个相反的论点。他对湖泊沉积中发现的可以追溯到上一次冰期的花粉进行了分析。

In contrast, Paul Colinvaux has offered a counterargument based on the analysis of pollen in lake sediments dating to the last ice age.

他发现这些沉积中的花粉含量非常低，这也就说明在末次冰期的高峰，白令陆桥地区更应该用“极地沙漠”这一术语来形容，因为这里几乎没有植被或其覆盖非常稀疏。

He found that the amount of pollen recovered in these sediments is so low that the Beringian landscape during the peak of the last glaciation was more likely to have been what he termed a “polar desert,” with little or only sparse vegetation.

因此，陆桥地区不可能存活大群的哺乳动物和人类猎人。

In no way was it possible that this region could have supported large herds of mammals and thus, human hunters.

古思莱反驳了这一观点。通过对白令地区沉积物中发现的猛犸象、马和野牛的骨头进行的放射性碳素分析，他指出这些骨头的年代测定是在冰川作用最强烈的时期。

Guthrie has argued against this view by pointing out that radiocarbon analysis of mammoth, horse, and bison bones from Beringian deposits revealed that the bones date to the period of most intense glaciation.

这个争论似乎一直处于僵持阶段，直到最近的一些研究有了重大的发现。

The argument seemed to be at a standstill until a number of recent studies resulted in a spectacular suite of new finds.

首先，科学家们发现了一个保留至今的、1000平方公里的白令植被区，这个植被区的年代被测定为是17000年前，也就是上一个冰期的高峰时期。

The first was the discovery of a 1,000-square-kilometer preserved patch of Beringian vegetation dating to just over 17,000 years ago—the peak of the last ice age.

这些植物被厚厚的火山灰所覆盖，并得以保存。

The plants were preserved under a thick ash fall from a volcanic eruption.

经过调查，正如古思莱预测的那样，这里发现了禾草、莎草、苔藓和很多其他种类的植物，它们几乎连绵不绝地覆盖着这个区域。

Investigations of the plants found grasses, sedges, mosses, and many other varieties in a nearly continuous cover, as was predicted by Guthrie.

然而这些植被根部细小，且没有土壤的形成。说明这里几乎不存在长期稳定的植物覆盖。这一发现也论证了科林沃克的一些观点。

But this vegetation had a thin root mat with no soil formation, demonstrating that there was little long-term stability in plant cover, a finding supporting some of the arguments of Colinvaux.

就目前已知的数据来看，最可信且最接近事实的解释就是：大型哺乳动物群是依靠这些连绵却又微薄的植被层生存的。

A mixture of continuous but thin vegetation supporting herds of large mammals is one that seems plausible and realistic with the available data.

The word “remnants” in the passage is closest in meaning to

The word “domain” in the passage is closest in meaning to

According to paragraph 3, all of the following are true of the Beringian landscape EXCEPT:

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.

According to paragraph 4, Guthrie believes that the teeth of ice-age fauna support which of the following conclusions?

According to paragraph 4, which of the following statements is true of the relationship between ice-age Beringian animals and their environment?

According to paragraph 5, how did Dale Guthrie use the information about radiocarbon analysis of bones from Beringian deposits?

Look at the four squares  that indicate where the following sentence could be added to the passage. Nevertheless, large animals managed to survive in Beringia.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

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.

The Beringia Landscape During the peak of the last ice age, northeast Asia (Siberia) and Alaska were connected by a broad land mass called the Bering Land Bridge. This land bridge existed because so much of Earth’s water was frozen in the great ice sheets that sea levels were over 100 meters lower than they are today. Between 25,000 and 10,000 years ago, Siberia, the Bering Land Bridge, and Alaska shared many environmental characteristics. These included a common mammalian fauna of large mammals, a common flora composed of broad grasslands as well as wind-swept dunes and tundra, and a common climate with cold, dry winters and somewhat warmer summers. The recognition that many aspects of the modern flora and fauna were present on both sides of the Bering Sea as remnants of the ice-age landscape led to this region being named Beringia. It is through Beringia that small groups of large mammal hunters, slowly expanding their hunting territories, eventually colonized North and South America. On this archaeologists generally agree, but that is where the agreement stops. One broad area of disagreement in explaining the peopling of the Americas is the domain of paleoecologists, but it is critical to understanding human history: what was Beringia like? The Beringian landscape was very different from what it is today.  Broad, windswept valleys; glaciated mountains; sparse vegetation; and less moisture created a rather forbidding land mass.  This land mass supported herds of now-extinct species of mammoth, bison, and horse and somewhat modern versions of caribou, musk ox, elk, and saiga antelope.  These grazers supported in turn a number of impressive carnivores, including the giant short-faced bear, the saber-tooth cat, and a large species of lion.  The presence of mammal species that require grassland vegetation has led Arctic biologist Dale Guthrie to argue that while cold and dry, there must have been broad areas of dense vegetation to support herds of mammoth, horse, and bison. Further, nearly all of the ice-age fauna had teeth that indicate an adaptation to grasses and sedges; they could not have been supported by a modern flora of mosses and lichens. Guthrie has also demonstrated that the landscape must have been subject to intense and continuous winds, especially in winter. He makes this argument based on the anatomy of horse and bison, which do not have the ability to search for food through deep snow cover. They need landscapes with strong winds that remove the winter snows, exposing the dry grasses beneath. Guthrie applied the term “mammoth steppe” to characterize this landscape. In contrast, Paul Colinvaux has offered a counterargument based on the analysis of pollen in lake sediments dating to the last ice age. He found that the amount of pollen recovered in these sediments is so low that the Beringian landscape during the peak of the last glaciation was more likely to have been what he termed a “polar desert,” with little or only sparse vegetation. In no way was it possible that this region could have supported large herds of mammals and thus, human hunters. Guthrie has argued against this view by pointing out that radiocarbon analysis of mammoth, horse, and bison bones from Beringian deposits revealed that the bones date to the period of most intense glaciation. The argument seemed to be at a standstill until a number of recent studies resulted in a spectacular suite of new finds. The first was the discovery of a 1,000-square-kilometer preserved patch of Beringian vegetation dating to just over 17,000 years ago—the peak of the last ice age. The plants were preserved under a thick ash fall from a volcanic eruption. Investigations of the plants found grasses, sedges, mosses, and many other varieties in a nearly continuous cover, as was predicted by Guthrie. But this vegetation had a thin root mat with no soil formation, demonstrating that there was little long-term stability in plant cover, a finding supporting some of the arguments of Colinvaux. A mixture of continuous but thin vegetation supporting herds of large mammals is one that seems plausible and realistic with the available data.