2018年6月大学英语六级听力常考时文：Population Growth思维导图

Thegrowthofpopulationduringthepastfewcenturiesisnoproofthatpopulationwillcontinuetogrowstraightupwardtowardinfinityanddoom.Onthecontrary,demographichistoryoffersevidencethatpopulationgrowthhasnotbeenatallconstant.AccordingtopaleoecologistEdwardDeevey,thepastmillionyearsshowthreemomentouschanges.Thefirst,arapidincreaseinpopulationaroundonemillionB.C.,followedtheinnovationsoftool-makingandtool-using.Butwhenthenewpowerfromtheuseoftoolshasbeenexploited,therateofworldpopulationgrowthfellandbecamealmoststable.Thenextrapidjumpinpopulationstartedperhaps10,000yearsago,whenmankindbegantokeepherds,plowandplanttheearth.Onceagainwheninitialproductivitygainshadbeenabsorbed,therateofpopulationgrowthabated.Thesetwoepisodessuggestthatthethirdgreatchange,thepresentrapidgrowth,whichbeganintheWestbetween250and350yearsago,mayalsoslowdownwhen,orif,technologybeginstoyieldfewerinnovations.Ofcourse,thecurrentknowledgerevolutionmaycontinuewithoutforeseeableend.Eitherway—contrarytopopularbeliefinconstantgeometricgrowth—populationcanbeexpectedinthelongruntoadjusttoproductivity.Andwhenonetakesthisview,populationgrowthisseentorepresenteconomicprogressandhumantriumphratherthansocialfailure.