学位英语

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 Sciences1, 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 settings2 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 activity3 may have led to anatomical changes4 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's5 “outdoor laboratory” in a natural clearing in Bossou6 Forest. Researchers allowed the wild chimpanzees access to different combinations of two different types of nut---the oil palm nut7, 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---prized 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 four8. 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 go9 by using everything available---even their mouths.

The second study, by Kimberley Hockings of Oxford Brookes University10, 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.

翻译：研究人员发现人类开始直立行走的原因

我们大多数人每天都走路而且手里搬着东西。这样的活动看似太简单，大多数人没有疑问。但是一个国际研究者(包括乔治?华盛顿大学哥伦比亚艺术与科学学院的Richmond博士)团队已经发现了人类直立行走可能源于数百万年以前适应搬运稀有的、高质量的资源。这些来自美国、英国、日本和葡萄牙的研究者研究了当代黑猩猩争抢食物时的行为特征，试图对什么样的生态环境竟然导致大猿(一种我们与现存的黑猩猩一样的600万年前的祖先)直立行走作出解释。

“这些黑猩猩居住的生态环境和我们最早的祖先开始直立行走时是相同的，”Richmond博士说。研究结果显示，当黑猩猩需要独占一种资源时，它们就从四肢行走转换为直立行走。由于直立行走可以解放它们的双手，这使得它们能搬更多的东西。久而久之，双足活动的强烈爆发可能导致了解剖学上的变化，因此这种变化也就成为自然选择的主题，在那种情况下，对食物或其他资源的争夺是十分激烈的。

有两项研究是在几内亚完成的。第一项研究是在京都大学博苏森林的一块天然空地——“室外实验室”进行的。研究者们允许森林里的黑猩猩能得到两种不同的坚果，一种叫油棕榈坚果，自然界随处可见，一种叫可乐果，自然环境中不常见。人们监控黑猩猩在下列三种情形下的行为：(a)只有油棕榈坚果;(b)只有少量的可乐果，大多数是油棕榈坚果;(c)大多数是可乐果，少数是油棕榈坚果。

当稀有的可乐果数量很少时，黑猩猩一次就会拿得多。同样，当大部分是可乐果时，黑猩猩对油棕榈坚果根本视而不见。黑猩猩认为可乐果才是珍贵的资源，并为得到可乐果激烈竞争。

处于这种激烈竞争的环境中，黑猩猩直立行走的频率增加了四倍。很显然，双足行走可以使它们拿走更多的稀有资源，而且，为了尽可能地一口气多拿，它们积极利用可用到的任何方法，甚至嘴巴。

第二项研究是在牛津布鲁克斯大学的Kimberley Hockings进行的。该研究历时14个月，主题是博苏的黑猩猩抢劫粮食，场景是它们不得不为稀有和不可预知的资源竞争。在这项研究中，黑猩猩35%的活动是直立行走。而这一次研究再一次证实了黑猩猩的直立行走与它们试图一次搬走尽可能多的东西有关。

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