2013年职称英语新增文章理工A(WORD版本)2013年职称英语新增文章理工A(WORD版本).doc

阅读理解 第四十八篇 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 dont question. But an international team of researchers, including Dr. Richmond from GWs 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 ecologieal 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 Universitys 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) wbem coula nuts were tbe majority available resource. When the rare co