阅读理解A
题干:FormostthinkerssincetheGreekphilosophers,itwasself-evidentthatthereissomethingcalledhumannature,somethingthatconstitutestheessenceofman.Therewerevariousviewsaboutwhatconstitutesit,buttherewasagreementthatsuchanessenceexists——thatistosay,thatthereissomethingbyvirtueofwhichmanisman.Thusmanwasdefinedasarationalbeing,asasocialanimal,ananimalthatcanmaketools,orasymbol-makinganimal.Morerecently,thistraditionalviewhasbeguntobequestioned.Onereasonforthischangewastheincreasingemphasisgiventothehistoricalapproachtoman.Anexaminationofthehistoryofhumanitysuggestedthatmaninourepochissodifferentfrommaninprevioustimesthatitseemedunrealistictoassumethatmenineveryagehavehadincommonsomethingthatcanbecalled"humannature."Thehistoricalapproachwasreinforced,particularlyintheUnitedStates,bystudiesinthefieldofculturalanthropology.Thestudyofprimitivepeopleshasdiscoveredsuchadiversityofcustoms,values,feelings,andthoughtsthatmanyanthropologistsarrivedattheconceptthatmanisbornasablanksheetofpaperonwhicheachculturewritesitstext.Anotherfactorcontributingtothetendencytodenytheassumptionofafixedhumannaturewasthattheconcepthassooftenbeenabusedasashieldbehindwhichthemostinhumanactsarecommitted.Inthenameofhumannature,forexample,Aristotleandmostthinkersuptotheeighteenthcenturydefendedslavery.Orinordertoprovetherationalityandnecessityofthecapitalistformofsociety,scholarshavetriedtomakeacaseforacquisitiveness,competitiveness,andselfishnessasinnatehumantraits.Popularly,onereferscynicallyto"humannature"inacceptingtheinevitabilityofsuchundesirablehumanbehaviorasgreed,murder,cheatingandlying.Anotherreasonforskepticismabouttheconceptofhumannatureprobablyliesintheinfluenceofevolutionarythinking.Oncemancametobeseenasdevelopingintheprocessofevolution,theideaofasubstancewhichiscontainedinhisessenceseemeduntenable.YetIbelieveitispreciselyfromanevolutionarystandpointthatwecanexpectnewinsightintotheproblemofthenatureofman.”
题目:
The word "untenable" (Line 3) in the last paragraph of the passage most probably means().