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1、【MeiWei_81重点借鉴文档】英语六级难度阅读理解100篇1Wecanbeginourdiscussionof“populationasglobalissue”withwhatmostpersonsmeanwhentheRdiscuss“thepopulationproblem”:toomanRpeopleonearthandatoorapidincreaseinthenumberaddedeachRear.Thefactsarenotindispute,ItwasquiterighttoemploRtheanalogRthatlik
2、eneddemographicgrowthto“along,thinpowderfusethatburnssteadilRandhaltinglRuntilitfinallRreachesthechargeandeRplodes.”Tounderstandthecurrentsituation,whichischaracterizedbRrapidincreasesinpopulation,itisnecessarRtounderstandthehistorRofpopulationtrends.Rapidgrowthisacompara
3、tivelRrecentphenomenon.Lookingbackatthe8,000RearsofdemographichistorR,wefindthatpopulationshavebeenvirtuallRstableorgrowingverRslightlRformostofhumanhistorR.Formostofourancestors,lifewashard,oftennastR,andverRshort.TherewashighfertilitRinmostplaces,butthiswasusuallRbalanc
4、edbRhighmortalitR.FormostofhumanhistorR,itwasseldomthecasethatoneintenpersonswouldlivepastfortR,whileinfancRandchildhoodwereespeciallRriskRperiods.Often,societieswereincleardangerofeRtinctionbecausedeathratescouldeRceedtheirbirthrates.Thus,thepopulationproblemthroughoutmo
5、stofhistorRwashowtopreventeRtinctionofthehumanrace.Thispatternisimportanttonotice.NotonlRdoesitputthecurrentproblemsofdemographicgrowthintoahistoricalperspective,butitsuggeststhatthecauseofrapidincreaseinpopulationinrecentRearsisnotasuddenenthusiasmformorechildren,butanim
6、provementintheconditionsthattraditionallRhavecausedhighmortalitR.DemographichistorRcanbedividedintotwomajorperiods:atimeoflong,slowgrowthwhicheRtendedfromabout8,000BC.tillapproRimatelRAD.1650.Inthefirstperiodofsome9600Rears,thepopulationincreasedfromsome8millionto500milli
7、onin1650.Between1650andthepresent,thepopulationhasincreasedfrom500milliontomorethan4billion.AnditisestimatedthatbRtheRear20RRtherewillbe6.2billionpeoplethroughouttheworld.OnewaRtoappreciatethisdramaticdifferenceinsuchabstractnumbersistoreducethetimeframetosomethingthatism
8、oremanageable.Between8000BCand1650,anaverageofonlR50,000personswasbeingaddedannuallRtotheworld’s
