英语六级考试备考晨读美文——Evolution and Wheels
<p> <span word="Evolution">Evolution</span> <span word="and">and</span> <span word="Wheels">Wheels</span></p><p> <span word="In">In</span> <span word="the">the</span> <span word="past">past</span>, <span word="evolutionary">evolutionary</span> <span word="biologists">biologists</span> <span word="contemplating">contemplating</span> <span word="the">the</span> <span word="absence">absence</span> <span word="of">of</span> <span word="wheels">wheels</span> <span word="in">in</span> <span word="nature">nature</span> <span word="agreed">agreed</span> <span word="that">that</span> <span word="the">the</span> <span word="explanation">explanation</span> <span word="was">was</span> <span word="not">not</span> <span word="undesirability">undesirability</span>: <span word="wheels">wheels</span> <span word="would">would</span> <span word="be">be</span> <span word="good">good</span> <span word="for">for</span> <span word="animals">animals</span>, <span word="just">just</span> <span word="as">as</span> <span word="they">they</span> <span word="are">are</span> <span word="for">for</span> <span word="us">us</span>. <span word="Animals">Animals</span> <span word="were">were</span> <span word="prevented">prevented</span> <span word="from">from</span> <span word="evolving">evolving</span> <span word="wheels">wheels</span>, <span word="the">the</span> <span word="biologists">biologists</span> <span word="reasoned">reasoned</span>, <span word="by">by</span> <span word="the">the</span> <span word="following">following</span> <span word="dilemma">dilemma</span>: <span word="living">living</span> <span word="cells">cells</span> <span word="in">in</span> <span word="an">an</span> <span word="animals">animals</span> <span word="body">body</span> <span word="are">are</span> <span word="connected">connected</span> <span word="to">to</span> <span word="the">the</span> <span word="heart">heart</span> <span word="by">by</span> <span word="blood">blood</span> <span word="vessels">vessels</span>, <span word="and">and</span> <span word="to">to</span> <span word="the">the</span> <span word="brain">brain</span> <span word="by">by</span> <span word="nerves">nerves</span>. <span word="Because">Because</span> <span word="a">a</span> <span word="rotating">rotating</span> <span word="joint">joint</span> <span word="is">is</span> <span word="essential">essential</span> <span word="to">to</span> <span word="a">a</span> <span word="wheel">wheel</span>, <span word="a">a</span> <span word="wheel">wheel</span> <span word="made">made</span> <span word="of">of</span> <span word="living">living</span> <span word="cells">cells</span> <span word="would">would</span> <span word="twist">twist</span> <span word="its">its</span> <span word="artery">artery</span> <span word="vein">vein</span> <span word="and">and</span> <span word="nerve">nerve</span> <span word="connections">connections</span> <span word="at">at</span> <span word="the">the</span> <span word="first">first</span> <span word="revolution">revolution</span>, <span word="making">making</span> <span word="living">living</span> <span word="impracticable">impracticable</span>. <span word="However">However</span>, <span word="there">there</span> <span word="is">is</span> <span word="a">a</span> <span word="flaw">flaw</span> <span word="in">in</span> <span word="the">the</span> <span word="argument">argument</span> <span word="that">that</span> <span word="the">the</span> <span word="evolution">evolution</span> <span word="of">of</span> <span word="wheeled">wheeled</span> <span word="animals">animals</span> <span word="was">was</span> <span word="thwarted">thwarted</span> <span word="by">by</span> <span word="the">the</span> <span word="insoluble">insoluble</span> <span word="joint">joint</span> <span word="problem">problem</span>. <span word="The">The</span> <span word="theory">theory</span> <span word="fails">fails</span> <span word="to">to</span> <span word="explain">explain</span> <span word="why">why</span> <span word="animals">animals</span> <span word="have">have</span> <span word="not">not</span> <span word="evolved">evolved</span> <span word="wheels">wheels</span> <span word="of">of</span> <span word="dead">dead</span> <span word="tissue">tissue</span> <span word="with">with</span> <span word="no">no</span> <span word="need">need</span> <span word="for">for</span> <span word="arteries">arteries</span> <span word="and">and</span> <span word="nerves">nerves</span>. <span word="Countless">Countless</span> <span word="animals">animals</span>, <span word="including">including</span> <span word="us">us</span>, <span word="bear">bear</span> <span word="external">external</span> <span word="structures">structures</span> <span word="without">without</span> <span word="blood">blood</span> <span word="supply">supply</span> <span word="or">or</span> <span word="nerves">nerves</span> - <span word="for">for</span> <span word="example">example</span>, <span word="our">our</span> <span word="hair">hair</span> <span word="and">and</span> <span word="fingernails">fingernails</span>, <span word="or">or</span> <span word="the">the</span> <span word="scales">scales</span>, <span word="claws">claws</span>, <span word="and">and</span> <span word="ho">ho</span> <span word="rns">rns</span> <span word="of">of</span> <span word="other">other</span> <span word="animals">animals</span>. <span word="Why">Why</span> <span word="have">have</span> <span word="rats">rats</span> <span word="not">not</span> <span word="evolved">evolved</span> <span word="bony">bony</span> <span word="wheels">wheels</span>, <span word="similar">similar</span> <span word="to">to</span> <span word="roller">roller</span> <span word="skates">skates</span>?<span word="Paws">Paws</span> <span word="might">might</span> <span word="be">be</span> <span word="more">more</span> <span word="useful">useful</span> <span word="than">than</span> <span word="wheels">wheels</span> <span word="in">in</span> <span word="some">some</span> <span word="situations">situations</span>, <span word="but">but</span> <span word="cats">cats</span> <span word="claws">claws</span> <span word="are">are</span> <span word="retractable">retractable</span>: <span word="why">why</span> <span word="not">not</span> <span word="retractable">retractable</span> <span word="wheels">wheels</span>?<span word="We">We</span> <span word="thus">thus</span> <span word="arrive">arrive</span> <span word="at">at</span> <span word="the">the</span> <span word="serious">serious</span> <span word="biological">biological</span> <span word="paradox">paradox</span> <span word="flippantly">flippantly</span> <span word="termed">termed</span> <span word="the">the</span> <span word="RRR">RRR</span> <span word="dilemma">dilemma</span>: <span word="natures">natures</span> <span word="failure">failure</span> <span word="to">to</span> <span word="produce">produce</span> <span word="rats">rats</span> <span word="with">with</span> <span word="retractable">retractable</span> <span word="roller">roller</span> <span word="skates">skates</span>.</p><p> </p>
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