2019-2020学年新教材高中英语 Unit 5 Into the wild讲义 外研版必修第一册

-1-Unit5Intothewild对于动物的灭绝，很多人猜测是气候的原因，其实，有时候人类才是动物生存最大的威胁。我们要保护动植物，与它们和谐相处。Climatechange,nothumanhunting,mayhavewipedoutthethylacine(袋狼),accordingtoanewstudybasedonDNAfromthylacines'bones.Themeat­eatingmarsupials(有袋动物)diedoutonmainlandAustraliaafewthousandyearsago,butsurvivedinTasmania,anislandofsoutheastAustraliaseparatedfromthemainland,untilthe1930s.Untilthen,scientistshadbelievedthecauseofthismainlandextinction(灭绝)wasincreasedactivityfromnativeAustraliansanddingoes(Australianwilddogs)．ScientistsbehindtheUniversityofAdelaidestudy,whichwaspublishedintheJournalofBiogeographyonThursday,collected51newthylacineDNAsamplesfromfossilbonesandmuseumskins—thelargestdatasetofthylacineDNAtodate.Thepaperconcludedthatclimatechangestartingabout4,000yearsago—inparticulardrierseasonscausedbytheweathersystemsknownasElNiño—SouthernOscillation(南方涛动)—waslikelythemaincauseofthemainlandextinction.TheancientDNAshowedthatthemainlandextinctionofthylacineswasrapid,andnottheresultoflossofgeneticdiversity.TherewasalsoevidenceofapopulationcrashinthylacinesinTasmaniaatthesameperiodoftime,reducingtheirnumbersandgeneticdiversity.AssociateProfessorJeremyAustinsaidTasmaniawouldhavebeenprotectedfrommainlandAustralia'swarmer,drierclimateduetoitshigherrainfall.Hearguedthatclimatechangewas“theonlythingthatcouldhavecaused,oratleaststarted,anextinctiononthemainlandandcausedapopulationcrashinTasmania.”“Theybothhappenedataboutthesametime,andtheothertwothingsthath-2-adbeentalkedaboutinthepastthatmayhavedriventhylacinestoextinctiononthemainlandweredingoesandhumans.Sotheonlyexplanationleftisclimatechange.Andbecausethepopulationcrashhappenedatthesametimeandthespecieswentextinctonthemainland,ourargumentisthatthere'sacommonthemethereandtheonlycommonthemeisthatthereisthischangeinclimate.”