學(xué)位英語

Researchers Discover Why Humans Began Walking Upright

Most of us walk and carry items in our hands every day. These are seemingly simple activities that the majority of us don't question. But an international team of researchers, including Dr. Richmond from GW's Columbian College of Arts and Sciences, have discovered that human walking upright, may have originated millions of years ago as an adaptation to carrying scarce, high-quality resources. The team of researchers from the U. S., England, Japan and Portugal investigated the behavior of modern-day chimpanzees as they competed for food resources, in an effort to understand what ecological settings would lead a large ape—one that resembles the 6 million-year old ancestor we shared in common with living chimpanzees—to walk on two legs.

"These chimpanzees provide a model of the ecological conditions under which our earliest ancestors might have begun walking on two legs," said Dr. Richmond.

The research findings suggest that chimpanzees switch to moving on two limbs instead of four in situations where they need to monopolize a resource. Standing on two legs allows them to carry much more at one time because it frees up their hands. Over time, intense bursts of bipedal activity may have led to anatomical changes that in turn became the subject of natural selection where competition for food or other resources was strong.

Two studies were conducted by the team in Guinea. The first study was conducted by the team in Kyoto University's “outdoor laboratory” in a natural clearing in Bossou Forest. Researchers allowed the wild chimpanzees access to different combinations of two different types of nut —the oil palm nut, which is naturally widely available, and the coula nut, which is not. The chimpanzees' behavior was monitored in three situations: (a) when only oil palm nuts were available, (b) when a small number of coula nuts were available, and (c) when coula nuts were the majority available resource.

When the rare coula nuts were available only in small numbers, the chimpanzees transported more at one time. Similarly, when coula nuts were the majority resource, he chimpanzees ignored the oil palm nuts altogether. The chimpanzees regarded the coula nuts as a more highly-Ffprized resource and competed for them more intensely.

In such high-competition settings, the frequency of cases in which the chimpanzees started moving on two legs increased by a factor of four. Not only was it obvious that bipedal movement allowed them to carry more of this precious resource, but also that they were actively trying to move as much as they could in one go by using everything available—even their mouths.

The second study, by Kimberley Hockings of Oxford Brookes University, was a 14-month study of Bossou chimpanzees crop-raiding, a situation in which they have to compete for rare and unpredictable resources. Here, 35 percent of the chimpanzees’activity involved some sort of bipedal movement, and once again, this behavior appeared to be linked to a clear attempt to carry as much as possible at one time.

練習(xí)：

36. Which of the following statements is NOT true according to the first two paragraphs?

A Many people question the simple human activities of walking and carrying items.

B Chimpanzee's behaviors may suggest why humans walk on two legs.

C Human walking upright is viewed as an adaptation to carrying precious resources.

D Our ancestors' ecological conditions resembled those of modern-day chimpanzees'.

37. Dr. Richmond conducted the experiment with the purpose of finding

A when humans began walking on two legs.

B what made our ancestors walk upright.

C what benefits walking upright brought to our ancestors.

D how walking upright helped chimpanzees monopolize resources.

38. Kyoto University's study discovered that chimpanzees

A regarded both types of nut as priced resources.

B preferred oil palm nuts to coula nuts.

C liked coula nuts better than oil palm nuts.

D ignored both types of nut altogether.

39. Why did the chimpanzees walk on two limbs during Kyoto University's experiment?

A Because they imitated the human way of walking just for fun.

B Because they wanted to please the researchers to get more coula nuts from them.

C Because they wanted to get to the nut-rich forest faster by walking that way.

D Because they wanted to carry more nuts with two free limbs.

40. What can we infer from the reading passage?

A Chimpanzees are in the same process of evolution as our ancestors were.

B Chimpanzees are similar to humans in many behaviors.

C Walking on two limbs and walking on four limbs each have their advantages.

D Human walking on two legs developed as a means of survival.

答案：ABCDD

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（責(zé)任編輯：vstara）

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