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  3. No Creatures can stride as human beings. They are not physically designed to support and balance a vertical body balanced on two

No Creatures can stride as human beings. They are not physically designed to support and balance a vertical body balanced on two

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问题     No Creatures can stride as human beings. They are not physically designed to support and balance a vertical body balanced on two long lower limbs, propelled forward by a foot engineered exclusively for body support and forward propulsion and to do so with a stride at high-speed locomotion. While other bipeds walk in a similar fashion, human walk is unique. Bipedalism by itself offers no comparison with the distinctive human gait form. And, significantly, no other biped can actually cover more than a tiny fraction of the walking distance that can be sustained by humans.
    Striding requires a special design of hip, knee, and ankle joints, plus an arched foot, plus long lower-limb bones. These "finishing touches" demanded extended evolutionary time. Striding provided numerous advantages over the simple stepping gait. For example, the ability to cover twice the distance with the same number of steps is a definite survival advantage. It also added much speed to running, more height to jumping.
    None of this would have been possible without, first, a foot equipped to support and balance an erect body and to produce the leverage necessary to propel the body forward in locomotion. The ape foot was not suited for this. A new kind of foot was essential if those hominids were to become full-scale bipeds. Indeed a pair of human feet has one-fourth of all the body’s 206 bones and 244 joints. Why this extraordinary number of bones and joints concentrated in such a small part of the body?(74)Because the intricate network of the many different parts required not only for supporting and balancing a heavy superstructure but to enable the multiple motions and actions, hundreds or thousands of times daily. No other part of the body comes even close to the amount and degree of stresses imposed on it.
    The human foot had to go through an extensive evolutionary development in which it underwent enormous design changes in cohering its 28 bones, 37 joints and 107 ligaments, and 32 muscles and tendons to adapt to the body weight and numerous torsions.(75)In fact, it probably wasn’t until only about 400, 000 years ago that early humans were fully striding, the final touch of human gait. Orthopedist Philip J. Mayer writes in the Orthopedic Review: "The development of a true stride on an orthopedic foot was the most crucial of all the steps of human evolution. " Nature had perhaps never undertaken an anatomical engineering project of such complexity.
Why is the human foot equipped the way it is?
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答案It is equipped to support and balance an erect body and to produce the leverage necessary topropel the body forward in locomotion．
解析 (根据文章第三段第一句，本句承上启下，解释人类脚的独特构造及原因。)
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本试题收录于： C类竞赛（非英语专业本科）题库大学生英语竞赛（NECCS）分类
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C类竞赛（非英语专业本科）

大学生英语竞赛（NECCS）

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