Immortality——No longer just a fantasy?
<p><span word="It">It</span>'<span word="s">s</span> <span word="highly">highly</span> <span word="unlikely">unlikely</span> <span word="that">that</span> <span word="a">a</span> <span word="human">human</span> <span word="could">could</span> <span word="live">live</span> <span word="forever">forever</span>. <span word="Even">Even</span> <span word="though">though</span> <span word="the">the</span> <span word="average">average</span> <span word="human">human</span> <span word="life">life</span> <span word="expectancy">expectancy</span> <span word="has">has</span> <span word="increased">increased</span> <span word="dramatically">dramatically</span> <span word="since">since</span> <span word="the">the</span> <span word="beginning">beginning</span> <span word="of">of</span> <span word="the">the</span> 20<span word="th">th</span> <span word="century">century</span>, <span word="it">it</span> <span word="won">won</span>'<span word="t">t</span> <span word="continue">continue</span> <span word="to">to</span> <span word="double">double</span> <span word="and">and</span> <span word="triple">triple</span> <span word="until">until</span> <span word="we">we</span>'<span word="re">re</span> <span word="living">living</span> <span word="for">for</span> <span word="hundreds">hundreds</span> <span word="of">of</span> <span word="years">years</span>. <span word="Some">Some</span> <span word="scientists">scientists</span> <span word="believe">believe</span> <span word="that">that</span> <span word="there">there</span> <span word="is">is</span> <span word="a">a</span> <span word="hard">hard</span>-<span word="coded">coded</span> <span word="maximum">maximum</span> <span word="life">life</span> <span word="expectancy">expectancy</span> <span word="for">for</span> <span word="humans">humans</span>, <span word="and">and</span> <span word="it">it</span>'<span word="s">s</span> <span word="probably">probably</span> <span word="somewhere">somewhere</span> <span word="around">around</span> 125 <span word="years">years</span> <span word="old">old</span>. <span word="One">One</span> <span word="theory">theory</span>, <span word="known">known</span> <span word="as">as</span> <span word="the">the</span> <span word="Hayflick">Hayflick</span> <span word="Limit">Limit</span> <span word="Theory">Theory</span>, <span word="suggests">suggests</span> <span word="that">that</span> <span word="the">the</span> <span word="cells">cells</span> <span word="in">in</span> <span word="the">the</span> <span word="human">human</span> <span word="body">body</span> <span word="may">may</span> <span word="only">only</span> <span word="divide">divide</span> <span word="and">and</span> <span word="copy">copy</span> <span word="themselves">themselves</span> <span word="a">a</span> <span word="fixed">fixed</span> <span word="number">number</span> <span word="of">of</span> <span word="times">times</span>, <span word="and">and</span> <span word="this">this</span> <span word="limit">limit</span> <span word="puts">puts</span> <span word="arestriction">arestriction</span> <span word="on">on</span> <span word="how">how</span> <span word="long">long</span> <span word="a">a</span> <span word="person">person</span> <span word="can">can</span> <span word="survive">survive</span>. <span word="Once">Once</span> <span word="cells">cells</span> <span word="cease">cease</span> <span word="reproducing">reproducing</span>, <span word="organs">organs</span> <span word="and">and</span> <span word="tissues">tissues</span> <span word="become">become</span> <span word="ineffective">ineffective</span> <span word="and">and</span> <span word="shut">shut</span> <span word="down">down</span>.</p><p><span word="On">On</span> <span word="the">the</span> <span word="other">other</span> <span word="hand">hand</span>, <span word="biological">biological</span> <span word="immortality">immortality</span> <span word="is">is</span> <span word="not">not</span> <span word="necessarily">necessarily</span> <span word="impossible">impossible</span>. <span word="One">One</span> <span word="species">species</span> <span word="of">of</span> <span word="jellyfish">jellyfish</span>, <span word="for">for</span> <span word="example">example</span>, <span word="known">known</span> <span word="as">as</span> <span word="the">the</span> <span word="Turritopsis">Turritopsis</span> <span word="nutricula">nutricula</span>, <span word="seems">seems</span> <span word="to">to</span> <span word="have">have</span> <span word="the">the</span> <span word="ability">ability</span> <span word="live">live</span> <span word="forever">forever</span> <span word="by">by</span> <span word="reversing">reversing</span> <span word="its">its</span> <span word="own">own</span> <span word="aging">aging</span> <span word="process">process</span> <span word="after">after</span> <span word="sexual">sexual</span> <span word="maturity">maturity</span>. <span word="This">This</span> <span word="type">type</span> <span word="of">of</span> <span word="discovery">discovery</span> <span word="may">may</span> <span word="provide">provide</span> <span word="comfort">comfort</span> <span word="to">to</span> <span word="futurists">futurists</span> <span word="who">who</span> <span word="hold">hold</span> <span word="out">out</span> <span word="hope">hope</span> <span word="that">that</span> <span word="human">human</span> <span word="immortality">immortality</span> <span word="is">is</span> <span word="right">right</span> <span word="around">around</span> <span word="the">the</span> <span word="corner">corner</span>. <span word="Scientists">Scientists</span> <span word="are">are</span> <span word="hard">hard</span> <span word="at">at</span> <span word="work">work</span> <span word="developing">developing</span> <span word="pills">pills</span> <span word="and">and</span> <span word="treatments">treatments</span> <span word="that">that</span> <span word="might">might</span> <span word="add">add</span> <span word="a">a</span> <span word="few">few</span> <span word="years">years</span> <span word="to">to</span> <span word="our">our</span> <span word="life">life</span>, <span word="but">but</span> <span word="their">their</span> <span word="search">search</span> <span word="is">is</span> <span word="hindered">hindered</span> <span word="by">by</span> <span word="how">how</span> <span word="long">long</span> <span word="human">human</span> <span word="beings">beings</span> <span word="already">already</span> <span word="live">live</span>. <span word="It">It</span>'<span word="s">s</span> <span word="difficult">difficult</span>, <span word="after">after</span> <span word="all">all</span>, <span word="to">to</span> <span word="construct">construct</span> <span word="a">a</span> <span word="scientific">scientific</span> <span word="experiment">experiment</span> <span word="or">or</span> <span word="clinicaltrial">clinicaltrial</span> <span word="that">that</span> <span word="may">may</span> <span word="last">last</span> <span word="for">for</span> <span word="more">more</span> <span word="than">than</span> <span word="a">a</span> <span word="hundred">hundred</span> <span word="years">years</span>.</p><p>小注1：表示人的寿命可以有三种说法，一种是<span word="life">life</span> <span word="expectancy">expectancy</span>，一种是<span word="longevity">longevity</span>，还有一种是<span word="life">life</span> <span word="span">span</span>。第一种最为通用，第二种偏学术，第三种显然最容易记忆容易书写，可根据情况选择。</p>
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