Linfield University DigitalCommons@Linfield Faculty Publications Faculty Scholarship & Creative Works 2017 The Extinction and De-Extinction of Species Helena Siipi University of Turku Leonard Finkelman Linfield College Follow this and additional works at: https://digitalcommons.linfield.edu/philfac_pubs Part of the Biology Commons, and the Philosophy of Science Commons DigitalCommons@Linfield Citation Siipi, Helena and Finkelman, Leonard, "The Extinction and De-Extinction of Species" (2017). Faculty Publications. Accepted Version. Submission 3. https://digitalcommons.linfield.edu/philfac_pubs/3 This Accepted Version is protected by copyright and/or related rights. It is brought to you for free via open access, courtesy of DigitalCommons@Linfield, with permission from the rights-holder(s). Your use of this Accepted Version must comply with the Terms of Use for material posted in DigitalCommons@Linfield, or with other stated terms (such as a Creative Commons license) indicated in the record and/or on the work itself. For more information, or if you have questions about permitted uses, please contact [email protected]. The extinction and de-extinction of species I. Introduction WhendeathcameforCelia,ittooktheformoftree.Heedlessofthedangerposed bybranchesoverladenwithsnow,CeliawanderedthroughthelandscapeofSpain’s OrdesanationalparkinJanuary2000.branchfellonherskullandcrushedit.So deathcameandtookher,leavingbodytobefoundbyparkrangersandlegacyto bemournedbyconservationistsaroundtheworld. Theconservationistsmournednotonlythedeathoftheorganism,butalsoan attendantdecreaseinbiodiversity.Celiawasthelastmemberofthesubspecies CaprapyrenaicapyrenaicaǡbetterknownasthePyreneanibex;whenshedied,so toodidthetaxonbecomeextinct. Wheremoststorieswouldend,Celia’sstory—oratleastthestoryofherDNA—had justbegun.Biologistshadcollectedtissuesamplesfromherbodyshortlybeforeher passing.Usingcellsculturedfromthosesamples,scientistsworkingforthe companyAdvancedCellTechnologysetaboutcloningCelia.Thefruitoftheirlabor wasbornin2009andsurvivedforsevenminutesbeforesuccumbingtolung problems.Celia’sclonedidrepresentmaterialtriumphofresurrectionbiology, morepopularlyknownasde-extinction(Folchetal2009;Pina-Aguilaretal2009). Atthemoment,numerousresearchgroupsaroundtheworldareworkingtowards de-extinctionofdifferentspecies.Effortsareunderway,forexample,toengineer passengerpigeon(EctopistesmigratoriusȌfromthegenomeoftherelatedband- tailedpigeon(PatagioenasfasciataȌ(Zimmer2013;O’Connor2015).Woolly mammothsmightbeclonedfromthetissuespreservedinthepermafrostofthe Siberiantundra(Loietal2011).Alternatively,anIndianelephant(Elephas maximusȌgenomemightserveastemplate(Salsberg2000).Severalgroupsare workingtowardscloningTasmaniantigers(Greer2009). Worriesregardinganthropogenicextinctionhavethisfar,atleastpartly,beenbased onviewaboutirreversibilityofextinction.AsJohan-WolfgangWägele(2014)puts it,“[…]thepoliticalsupportforactionsthatcanmitigatebiodiversitylossesishalf- heartedandinadequate.Thisisextremelydangerous,becauselossofspeciesis irreversibleǤ[…]lifeforms,oncelost,cannotregenerate.”Thedevelopmentsin resurrectionbiologyquestionthisvarybasictenetofconservation.Resurrection biologyistakentoimplythat“therevivalofanextinctspeciesisnolongerfantasy” (Zimmer2013)orthat“extinctionmightnotbeforever[…]”(Redfordetal.2013). Consequently,developmentsinresurrectionbiologyareoftenmetwithenthusiasm. Yet,thepossibilityoffuturesuccessinresurrectionbiologyraisesmanyquestions. Someareempirical:canresurrectedspeciesbereintroducedintothewild?What aretheenvironmentalcostsandbenefitsofspeciesresurrection?Otherquestions arephilosophical.Inthisessayweaddresssomeofthesephilosophicalquestions.In particular,weconsiderwhetherthegoalsofresurrectionbiologyareconceptually coherent.Ourinquiryanalysestworelatedconceptsrelevanttotheresurrection: theconceptofextinctionandtheconceptofspecies.Throughtheanalysesofthem wedemonstrate,first,theimplicationsthatresurrectionbiologymayhaveforthe conceptualfoundationsoflifesciences,andsecond,implicationsthatdifferent speciesconceptsandunderstandingsofextinctionmayhaveonthestatusof animalsproducedbyde-extinctiontechnologies. Beforeengagingourinquiry,wewillfirstbrieflydescribe“de-extinction”techniques andtechnologiesinPartIIbelow.InPartIIIwepresentfourdifferentspecies conceptsandthreedifferentwaysofunderstandingextinction.Wealsoraisethe challengeofseeingextinctionassomethingnecessarilyfinal.InPartIVweapplythe presentedconceptstoresurrectionbiologyanddiscussthepossiblewaysoffitting resurrectionbiologytogetherwiththeideaoffinalityofextinction.Inpartwe discussthespeciesandextinctionconceptsthatarecompatiblewithresurrection biologyifextinctionisnotseenasnecessarilyfinal.Finally,weconcludeinPartVI withthoughtsonfurtherimplicationsofouranalysis. II. De-extinction Thegoalofresurrectionbiologyisdeceptivelysimpleinitsarticulation:itistomake extinctspeciesextantoncemore.Aswewillsee,however,thissimpleformulation begsnumberoftheoreticalquestions.Phrasedmoreneutrally,resurrection biologyaimstoproduceanimalsthatare(tohighdegree)similartomembersof extinctspecies.Thesekindsofanimalscanbecreatedeitherthroughselective breedingorthroughdifferentapplicationsofcloningtechnologies. Resurrectionbiology’searliestattemptstooktheformof“back-breeding”(Oksanen ƬSiipi2014).Throughwell-practicedmethodsofhusbandry,skilledbreedersmay crossextantlineagestowardstheendofreplicatingphenotypes,andperhapseven genotypes,ofclosely-relatedextinctlineages.Thismethodisstructurallyidenticalto otherformsofartificialselection,withonekeydifference:insteadofproducingnew organismsinexistingbreedsornewtypesofbreeds,thegoalistoproduceanimals thataresimilartomembersofextinctbreeds.Morerecently,conservationistshave consideredthepossibilitythatthistechnique,alsoknownas“lineagefusion,”could resurrectextinctsubspeciesofGalápagostortoises(Poulakakisetal2008;Garrick etal2014). Themorepublicizedversionsofresurrectionbiologyarebasedonapplyingthe cloningtechnologies(Zimmer2013).Infact,therearetwomethodsbywhichthe goalofresurrectioncanbeachieved:throughsomaticcellnucleartransferor throughgeneticengineering(SherkowƬGreely2013;OksanenƬSiipi2014). Resurrectionbysomaticcellnucleartransfer(abbreviatedtoSCNT)isquitesimilar to“ordinary”cloningexemplifiedinthefamedsheepDolly.SCNT’susein resurrectionbiologyispopularizedbyworkssuchasJurassicParkanditis sometimescalledcross-speciescloningǤ(Wilmutetal1999;Zimmer2013.)The resurrectionprocessbeginswiththecultivationofsomaticcell’snucleusfromthe tissueoftheextinctspecies.Thatnucleus,includingitsfullcomplementofgenetic material,istheninsertedintoanenucleatedeggofanotherspecies.memberof thatspeciesworksassurrogatemother.Whencarriedtoterm,theprocedure producesnearly-identicaltwinstothemembersoftheextinctspecies;theonly geneticdifferenceswouldbeintheorganisms’mitochondrialandimmunecellDNA (Hiendlederetal2004). SCNTisthemeansbywhichCeliawascloned.Thismethodisalsostudiedas meansofresurrectingspeciessuchasgastricbroodingfrogs(RheobatrachussilusȌ (Archer2013),woollymammoths(MammuthusprimigeniusȌ(Loietal2011),and Tasmaniantigers(ThylacinuscynocephalusȌ(Greer2009). Asmethodofresurrectionbiology,geneticengineeringissimilartoSCNTinthat anorganismisproducedfromtheimplantationofmodifiedembryointo surrogatemother;thedifferencebetweenthemethodsliesintheoriginofthe embryo’sgeneticmaterial.De-extinctionthroughgeneticengineeringbeginswith thecultivationofgeneticmaterialfrommemberofsistertaxontothetarget extinctspecies,ratherthanfromtissueoftheextinctspeciesitself.Whengenomic differencesbetweentheextinctspeciesanditssistertaxoncanbeidentified,the geneticmaterialfromthedonororganismcanbemodifiedtomatchtheextinct species’genome.Themodifiedgeneticmaterialisplacedintothedonornucleus, whichistheninsertedintoanenucleatedegg,whichisinturnimplantedintothe surrogatemother.Thismethodhastheadvantageofpotentiallyincreasingthe geneticsimilaritybetweencloneanddonororganism:engineersmightreconstitute thedonor’smitochrondrialDNA,therebyoffsettingpotentialproblemsintheSCNT processsuchasthoseoutlinedbyHiendlederetal(2004). passengerpigeon(EctopistesmigratoriusȌmightberesurrectedthiswayfromthe genomeoftherelatedband-tailedpigeon(PatagioenasfasciataȌ(Zimmer2013; O’Connor2015).HornerƬGorman(2009)goasfarassuggestingthatnon-avian dinosaursmightbeengineeredfromthegenomeofdomesticchicken;Bhullaretal (2015)havemadeprogressinderivingdinosaurphenotypefromthechicken’s genotype1Ǥ 1Thereproductionofnonaviandinosaurtraitsdiffersfromtheresurrectionofthe passengerpigeoninoneimportantrespect:thelatterwouldbetheresultof replicatinganorganism’sentiregenomewhereastheformerwouldbetheresultof replicatinganorganism’sgenesequences.Nevertheless,thisisdifferenceof degreeratherthanofkind;certainly,ifsufficientnumberofnonaviandinosaur traitsweretobereplicatedthentheentiretyofnonaviandinosaurphenotype Eachofthesemethodsofresurrectionbiologyfacespracticalobstaclesand limitations.Towit:back-breedingcanonlyresurrectextincttaxabelowthespecies category;SCNTandgeneticengineeringareviableonlyforextincttaxawhose developmentalenvironmentsweresufficientlysimilartothoseofsurrogates; geneticengineeringassumesantecedentknowledgeoftheextincttaxon’sgenome. Nevertheless,manyoftheobstaclesarecontingentonthestateofourtechnological art.Thesuccessofresurrectionbiologymaynotbeinevitable,butitmaybelikelier thannot(Stone2003;Zimmer2013). Inadditiontothesepracticalobstacles,however,therearesignificantconceptual challengestobemet.Inthispaperwequestionthecommonviewsregardingthe successofresurrectionbiology.Itisnotself-evidentthatanimalscreatedbyabove describedmethodsaremembersoftheextinctspecies(e.g.Pyreneanibex,woolly