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Don'twashthosefossils!
StandardmuseumpracticecanwashawayDNA.
1.Washing,brushingandvarnishingfossils—allstandardconservationtreatmentsusedbymanyfossilhuntersandmuseumcuratorsalike—vastlyreducesthechancesofrecoveringancientDNA.
2.Instead,excavatorsshouldbehandlingatleastsomeoftheirbountywithgloves,andfreezingsamplesastheyarefound,dirtandall,concludesapaperintheProceedingsoftheNationalAcademyofSciencestoday.
3.AlthoughmanypalaeontologistsknowanecdotallythatthisisthebestwaytouptheoddsofextractinggoodDNA,Eva-MariaGeigloftheJacquesMonodInstituteinParis,France,andhercolleagueshavenowshownjusthowimportantconservationpracticescanbe.Thisinformation,theysay,needstobehammeredhomeamongthepeoplewhoareactuallyoutinthefielddiggingupbones.
4.Geiglandhercolleagueslookedat3,200-year-oldfossilbonesbelongingtoasingleindividualofanextinctcattlespecies,calledanaurochs.ThefossilsweredugupatasiteinFranceattwodifferenttimes—eitherin1947,andstoredinamuseumcollection,orin2004,andconservedinsterileconditionsat-20oC.
5.Theteam'sattemptstoextractDNAfromthe1947bonesallfailed.Thenewlyexcavatedfossils,however,allyieldedDNA.
6.Becausetheboneshadbeenburiedforthesameamountoftime,andinthesameconditions,theconservationmethodhadtobetoblamesaysGeigl."AsmuchDNAwasdegradedinthese57yearsasinthe3,200yearsbefore,"shesays.
Washin,washout
7.Becausemanypalaeontologistsbasetheirworkontheshapeoffossilsalone,theirmethodsofconservationarenotdesignedtopreserveDNA,Geiglexplains.
8.Thebiggestproblemishowtheyarecleaned.Fossilsareoftenwashedtogetheron-siteinalargebath,whichcanallowwater—andcontaminantsintheformofcontemporaryDNA—topermeateintotheporousbones."NotonlyistheauthenticDNAgettingwashedout,butcontaminationisgettingwashedin,"saysGeigl.
9.MostancientDNAspecialistsknowthisalready,saysHendrikPoinar,anevolutionarygeneticistatMcMasterUniversityinOntario,Canada.Butthatdoesn'tmeanthatbestpracticehasbecomewidespreadamongthosewhoactuallyfindthefossils.
10.GettingholdoffossilsthathavebeenpreservedwiththeirDNAinmindreliesoncloserelationshipsbetweenlab-basedgeneticistsandtheexcavators,sayspalaeogeneticistSvantePbooftheMaxPlanckInstituteforEvolutionaryAnthropologyinLeipzig,Germany.Andthatonlyoccursinexceptionalcases,hesays.
11.Pbo'steam,whichhasbeensequencingNeanderthalDNA,continuallyfacestheseproblems."WhenyouwanttostudyancienthumanandNeanderthalremains,there'sabigissueofcontaminationwithcontemporaryhumanDNA,"hesays.
12.Thisdoesn'tmeanthatallmuseumspecimensarefatallyflawed,notesPbo.TheNeanderthalfossilsthatwererecentlysequencedinhisownlab,forexample,hadbeenpartofamuseumcollectiontreatedinthetraditionalway.ButPboiskeentoseesamplesoffossilsfromeverymajorfindpreservedinlinewithGeigl'srecommendations—justincase.
Warmandwet
13.Geiglherselfbelievesthat,withcooperationbetweenbenchandfieldresearchers,preservingfossilsproperlycouldopenupavenuesofdiscoverythathavelongbeenassumedclosed.
14.Muchhumanculturaldevelopmenttookplaceintemperateregions.DNAdoesnotsurvivewellinwarmenvironmentsinthefirstplace,andcanvanishwhenfossilsarewashedandtreated.Forthisreason,Geiglsays,mostancientDNAstudieshavebeendoneonpermafrostsamples,suchasthewoollymammoth,oronremainsshelteredfromtheelementsincoldcaves—includingcavebearandNeanderthalfossils.
15.Betterconservationmethods,andafocusonfreshfossils,couldboostDNAextractionfrommoredelicatespecimens,saysGeigl.Andthatcouldshedmorelightonthestoryofhumanevolution.
(640wordsnature)
Glossary
Palaeontologists古生物學(xué)家
Aurochs歐洲野牛
Neanderthal(人類學(xué))尼安德特人，舊石器時代的古人類。
Permafrost(地理)永凍層
Questions1-6
AnswerthefollowingquestionsbyusingNOMORETHANTHREEWORDSforeachanswer.
1.Howdidpeopletraditionallytreatfossils?
2.WhatsuggestionsdoGeiglandhercolleaguesgiveonwhatshouldbedonewhenfossilsarefound?
3.Whatproblemsmaybeposediffossilbonesarewashedon-site?NameONE.
4.WhatcharacteristicdofossilboneshavetomakethemsusceptibletobecontaminatedwithcontemporaryDNAwhentheyarewashed?
5.Whatcouldbebetterunderstoodwhenconservationtreatmentsareimproved?
6.Thepassagementionedseveralanimalspeciesstudiedbyresearchers.Howmanyofthemarementioned?
Questions7-11
Dothefollowingstatementsagreewiththeinformationgiveninthepassage?PleasewriteTRUEifthestatementagreeswiththewriterFALSEifthestatementdoesnotagreewiththewriterNOTGIVENifthereisnoinformationaboutthisinthepassage.
7.IntheirpaperpublishedintheProceedingsoftheNationalAcademyofSciences，GeiglandhercolleagueshaveshownwhatconservationpracticesshouldbefollowedtopreserveancientDNA.
8.ThefossilbonesthatGeiglandhercolleaguesstudiedareallfromthesameaurochs.
9.Geneticistsdon'thavetoworkonsite.
10.OnlynewlyexcavatedfossilbonesusingnewconservationmethodssuggestedbyGeiglandhercolleaguescontainancientDNA.
11.Paaboisstillworriedaboutthepotentialproblemscausedbytreatmentsoffossilsintraditionalway.
Questions12-13
CompletethefollowingthestatementsbychoosingletterA-Dforeachanswer.
12.“Thisinformation”inparagraph3indicates:
[A]ItiscriticaltofollowproperpracticesinpreservingancientDNA.
[B]ThebestwayofgettinggoodDNAistohandlefossilswithgloves.
[C]Fossilhuntersshouldwearhome-madehammerswhilediggingupbones.
[D]Manypalaeontologistsknowhowoneshoulddointreatingfossils.
13.ThestudyconductedbyGeiglandhercolleaguessuggests:
[A]thefactthatancientDNAcannotberecoveredfromfossilbonesexcavatedinthepast.
[B]thecorrelationbetweentheamountofburyingtimeandthatoftherecoveredDNA.
[C]thepaceatwhichDNAdegrades.
[D]thecorrelationbetweenconservationpracticesanddegradationofDNA.
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Asianeconomieswillcontinuetoexpandrapidlyinthenexttwoyearsonthebackofforeigninvestments,exportsanddomesticdemand,butwillnotbefreeofworries,accordingtoarecentsecuritiescompanyeconomicreport.Massiveinfrastructurespending,thebenefitsofpastinvestmentsandderegulationandgrowingregionaltradewillpushalongregionalgrowth.
ThereporttippedChina’sgrossdomesticproducttogrowby9.5percentin1996and10.5percentin1997,andHongKong’stogrowby4.3and5.0percent.Singapore’srealGDPwasforecasttogrowby7.6and7.4percent,Malaysia’sby8.6and8.1percent,Thailand’sby8.8and8.4percent,Indonesia’sby7.3and7.1percentandPhilippines’by5.6and5.8percent.
“However,allisnotrosy,”cautionedthereport,whichlistedoverheatingastheregion’sbiggestchallengeintheshorttermandskilled-laborshortagesinthelongrun.
Itcitedstrainsfromrapidgrowththathadbeguntostretchcurrentaccountdeficitsandspurinflationinsomeregionaleconomies,whichcouldpreventtheircentralbanksfromloweringinterestrates.
“Thisimpliesthateconomicvulnerabilitytounexpectedshockswillremainhigh,”thereportsaid,forecastingafurthertighteningofmonetarypolicyincountriessuchasthePhilippinesandMalaysia,andnosignificanteasinginThailand,IndonesiaandChina.
CrosbySecuritiesalsocitedmassivenewinvestmentprogramsgeneratedbydemandsoninfrastructuresuchaspower,telecommunicationsandtransportwhichhadfuelledover-heating.
ItsaidAsiawouldalsofaceabiggerchallengefromnewlyderegulatingeconomiesinEasternEuropewhichofferedlowercostsandbetter-educatedworkerstoforeigninvestors.
Asia’smainforeigninvestorsshould,however,continuetoexpandtheirpresenceintheregion,thesecuritieshousesaid,notingnewtrendsofintra-Asianinvestment.
Singaporeisshiftingitslowervalue-addeddiscdriveandelectronicsindustrytoMalaysia,whichinturnismovingsomeofitsgarment-makingandconsumerelectronicsmanufacturingtoIndonesiaandThailand.Thailand,MalaysiaandSingaporeareincreasinglyinvestinginVietNam,MyanmarandLaos.
“Asiawillbenefitfromthistrendinseveralways,”thereportsaid.
()1Asiaeconomywillcontinuetogrowbecauseof_____________.
A.foreigninvestmentB.demandsinAsiancountries.
C.exportD.alloftheabove
()2Inthenext2years,thehighesteconomicgrowthwillappearin____________.
A.SingaporeB.Thailand
C.HongKongD.China
()3Yearslater,theprobleminAsianeconomymaybe_________________.
A.toolittleinvestmentB.toomuchinvestment
C.notenoughqualifiedlaborsD.monetaryinstability
()4Accordingtothisreport,economicchangesinEastEuropeare___________.
A.harmfulB.challenging
C.helpfulD.useless
()5ThereportisabouttheprospectofAsianeconomy.
A.optimisticB.pessimistic
C.moreoptimisticthanpessimisticD.morepessimisticthanoptimistic
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