EvolvingTomorrow
GeneticEngineeringandtheEvolutionaryFuture oftheAnthropocene
AsherD.Cutter
DepartmentofEcology&EvolutionaryBiology,UniversityofToronto
GreatClarendonStreet,Oxford,OX26DP, UnitedKingdom
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ISBN978–0–19–887452–2
DOI:10.1093/oso/9780198874522.001.0001
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Formymostpreciousexperimentsinevolution,BeatrixandOona,andallthekin oftheirgeneration:Fletcher,Lucy,Damon,Jasper,EddieArlene,Hildegard,andArlo.
Part2Evolutionaryfutures
Preface
Icanpromiseyouthatlifetoday,despitemillenniaofprofoundevolutionarychange,will continuetoevolvetomorrow.Someofthatevolutiontospecies’featureshasnothingto dowithhumanity.Someofitarisesasanincidentalbyproductofourexistence.And someevolutionresultsdirectlyfromintentionalinterventionbypeople.Thisbookwill scrutinizehowallofthatevolutionarychangecanhappen,howmodern-daygenetic engineeringcaninfluenceit,andwhatconsequencesoftheseforceswecanexpectto seeinthefutureoftheAnthropoceneera.
Part1ofthisbook, Theheartsofnature,exploreshowlivingorganismschangeover time.Overthesefirst10chapters,we’llunearthnature’sevolutionaryforcesandhow theseforcesinterplaywithgenetics.Part1explainstheintricaciesofgeneticbiotechnologieslikeCRISPR-Cas9genomeediting,andhowCRISPR-Cas9,whenusedtomake genedrives,nowpermitshumanstomodifythegenomesofeverysingleindividualinany speciesofourchoosing.Imakethecasethatthiskindofgeneticengineering,“genetic welding,”unleashedintothewild,willpresentanewforceofevolution.Ishowjusthow fastevolutioncanproceedtochangeaspecies,andwe’lllearnwhatitisthatmakesa speciesaspeciesinthefirstplace.Iinfusetheconceptualpointswithincredibletalesof organismalbiology:ofmelanicsquirrelsandblanchedmice,oftomatoesandtheopsin genesthatletussee,ofcrocodilesandskunkmusk,ofchimericsexandofthevirtues ofchickens.Idrawonmyownexperienceoflivingonthreecontinentsandconducting researchinthelabandinthefieldoftropicalhabitatsoverthepastfewdecades.
Part2, Evolutionaryfutures,shiftsattentiontowardtheapplicationsandimplications ofusingevolutionaryforces,andgeneticengineering,tomanipulateorganismsandto createnewspecies.We’llwalkthroughtheecosystemconsequencesofspeciesgainand lossinourcurrentAnthropoceneera.We’lldeliberatetheins-and-outsofde-extinction withaurochsandwoollymammoths,ofrewildingwithwisent(Europeanbison)and chestnuts,of“pest”controloverinvasivespecieslikehippos,allasmodernlarge-scale incarnationsofecologicalrestoration.We’llponderthefigurativedragonsthatwewould needtoconfrontinapplyinggeneticweldingtocreateandintroducenewspeciesinto ecosystems.Fromtheviewofgenetics,humansarejustanotheranimal.Inconsidering theethicalsoupofgeneticengineeringofourownspecies,Ihighlightlessonsfrombody modificationandinvitrofertilization,identifyingthepotentialforgeneticweldingof humangenomestounleashwhatIterm guerrillaeugenics.Isharemyowninternalconflictsinthesemultifacetedethicaldiscussions.We’lllaybarethecompetingandoften internallyinconsistentviewsofwhatis“wild”andwhatpeopledesirefrom“nature,” theoft-neglectedconsiderationsthatarecrucialindecidinghowhumansshoulddeploy orpreventevolutionaryengineeringandgeneticweldinginecosystems.Whatwedecide
todoasaglobalsocietywillshapethekindofevolutionarychangethatwillaccumulate intheworldoftomorrowandthroughoutthenextmillennia.
Inpreparing EvolvingTomorrow,I’vehadthegoodfortuneofgoodcolleaguesand goodsupports.Forexpertconsultationonmyblue-moonquestions,Iamgrateful tothekindandquickmindsofSpencerC.H.Barrett,JohnCalarco,BelindaChang, MarcT.J.Johnson,LukeMahler,ShelbyRiskin,F.HelenRodd,NjalRollinson,and StephenWright.IalsobenefitedfromGrahamCoop’slucidinsightsintogeneticsdeliveredonaverysnowyeveningforthe2019DarwinDaylectureattheUniversityof Toronto.ThanksalsogotoAshleyReynoldsforassistancewiththeteachingcollectionofmammalbonesintheDepartmentofEcology&EvolutionaryBiology.Iam fortunateforthefavorandencouragementofcarefulandthoughtfulreadersofdraft versionsofchapters.Inparticular,I’mgratefultoBelindaChang,ZoeClarke,Steven Coyne,BeatrixCutter,OonaCutter,MarcT.J.Johnson,NicoleMideo,ShelbyRiskin, Yee-FanSun,JasonWeir,andStephenWright.ThankyoualsototheEvolutionary GeneticsDiscussionGroupandthemembersofmyresearchteamattheUniversityof Toronto,fordiscussionofearlyversionsofchapters,includingEniolayeBalogun,Maia Dall’Acqua,DanielFusca,KarlGrieshop,VedikaJha,KatjaKasimatis,ElseMikkelsen, ChristineRehaluk,RebeccaSchalkowski,MaríaTocora,AthmajaViswanath,Sabrina Zaidi,andLinyiZhang.I’mveryappreciativeofmyproductioneditor,KatieLakina, forkeepingitallinorder.I’mindebtedtomyeditor,IanSherman,atOxfordUniversity Press,forhisencouragementandfrankadviceinworkingfromtheproposalthroughto bookfinalization,andtothecollectionofthoughtfulanonymousreviewersoftheinitial bookproposalwhosharedexceptionalconstructivefeedback.Oneaccidentalblessing oftheCOVID-19pandemicisthatitgiftedmetheluxuryofwritingthisbookfrom homewhilesurroundedbyfamily.Iamcontinuallygratefulfortheloveandsupportof Yee-Fan,Oona,andBeatrix,inallthosemomentswhenIneededitmost.
Mygrowthasascientistwasshapedbyalongtrainofbiologicalmentorswhotook greatcareinguidingmydevelopment,startingfromwhenIwasateenager.Thankyou, LeoP.Kenney,NortonH.Nickerson,SaraM.Lewis,StephenH.Levine,MichaelP. Ghiglieri,ChristopherA.M.Reid,LeticiaAvilés,SamuelWard,DeborahCharlesworth, andBrianCharlesworth.WhileIamsoverygratefulforthepersonalcontributionsof theseindividualpeopletomyparticularscientificdevelopment,mydebtrunsdeeper: totheentirecommunityoftheworld’sscientists,pastandpresent.Theopensharingof theirfindingsanddata,aswellastheblossomingandfadingofideasacrossthedecades asrecordedinthescientificliterature,madethisbookpossibleandallthemoreenjoyable towrite.Theinquisitivenessandrigorofscientificresearchersindisciplinesofallstripes hasgiveneveryoneofusthiscurrentunderstandingoftheworld.
InwritingthisbookinToronto,Ontario,Igratefullyacknowledgethislandthat isnowhometodiversepeoplesasthetraditionalterritoryoftheMississaugasofthe Credit,theAnishnabeg,theChippewa,theHaudenosaunee,theWendatpeoples,and theirancestors.
Abbreviations
BRCA1: Breastcancergene1,foundinhumangenomeswithmutatedgenevariants thatconferahighlikelihoodofdevelopingbreastorovariancancerinone’s lifetime.
Cas9: CRISPR-associatedprotein9,encodedbygenesfoundinbacteriaand archaeathatisinvolvedindefenseagainstphagevirusesandthathasbeen co-optedinbiotechnologyforgenomeediting.
CCR5: C-Cchemokinereceptortype5gene,foundinhumangenomeswitha mutatedgenevariantassociatedwithresistancetoinfectionbythehuman immunodeficiencyvirus(HIV).
ClvR: Cleaveandrescuegenedrive,akindofgeneticallyengineeredselfishgenetic elementsystemthatactstoincreaseitsabundanceinapopulationasit transmitsitselffromgenerationtogeneration.
CRISPR: Clusteredregularlyinterspersedshortpalindromicrepeats,regionsofbacterialandarchaealgenomesthatencodealibraryofphageviralDNAto targetaspartoftheirimmunesystem,portionsofwhichgetexpressedto formguideRNAstoworkinconcertwithCas9proteinstocutinvadingviral DNA,asystemthathasbeenco-optedforbiotechnologicaluseingenetic engineering.
dCas9: deadCRISPR-associatedprotein9,ageneticallymodifiedversionofCas9 proteinthatdisablestheabilitytocutDNA.
DMI: Dobzhansky-Mullerincompatibility,adetrimentalinteractionbetween genesthatgetsrevealedwheninterspecieshybridsdevelop.
DNA: Deoxyribonucleicacid,thechemicalresponsibleforstoringheritablematerialinanimals,plants,fungi,bacteria,archaea,andDNA-basedviruses.
GDO: Genedriveorganism,ageneticallymodifiedorganismthatencodesa syntheticgenedriveinitsgenome.
GE: Geneticallyengineered,synonymforgeneticallymodifiedbyvirtueof alterationsofthegenomethroughdirectedmolecularbiologytechniques, typicallyinvolvingtransgenicDNA.
GFP: Greenfluorescentprotein,aproteinfoundnaturallyinthegenomesofsome jellyfishspeciesthathasbeenco-optedforuseinexperimentalmolecular biologyduetoitsabilitytoemitlightwhenexposedtoUVillumination.
GMO: Geneticallymodifiedorganism,anorganismwhosegenomeincludes changesfromgeneticengineering,usuallyoftransgenicorigin.
Abbreviations
GPCR: G-protein-coupledreceptor,akindofproteinthatispartofalargefamily ofproteinsinanimalgenomesthatlocalizetocellmembranesandoften havefunctionsrelatedtotransductionofinformationintothecell,including sensationoflightorodor.
HDR: Homologydirectedrepair,ahighlyaccuratecellularmechanismthatfixes damagedDNAbyusingasimilarsequenceofDNAasthetemplatefor repair,usuallyusingahomologouschromosomeundernaturalcircumstancesbutthatcanalsouseatemplateofDNAprovidedbyaresearcher whenconductinggenomeediting.
HGT: Horizontalgenetransfer,themovementofgeneticmaterialfromonespecies toanotherspecies,usuallyinthecontextofnaturalmicrobialmechanisms ofDNAexchange.
HHGE: Heritablehumangenomeediting,geneticengineeringappliedtohuman cellsthatwillleadtotransmissionofthegeneticchangesacrossgenerations.
IUCN: InternationalUnionforConservationofNature,anongovernmentalorganizationwithobserverstatuswithintheUnitedNationsandexpertisein environmentalissues.
IVF: Invitrofertilization,amedicalandveterinarytechniqueforhumansand othermammalstofacilitatefusionofgametesinaPetridishoutsidethebody forsubsequenttransfertothewombofahostfemaletoenablegestationof theresultingembryoandfetus.
MC1R: Melanocortin-1receptorprotein,atypeofproteinencodedingenomesof mammalsandothervertebrateswithakeyroleinthepathwayresponsible forproductionofmelaninpigments.
mRNA: Messengerribonucleicacid,theintermediarymoleculethatresultsfrom transcriptionofageneinthegenomethatwillthengettranslatedintoa protein.
MRSA: Methicillin-resistant Staphylococcusaureus,apathogenicbacteriumresponsibleforstaphinfectionsthatisnottreatablebymanyantibiotics.
NHEJ: Nonhomologousendjoining,amechanismofDNArepairthatisproneto introduceinsertionordeletionchangestotheDNAsequenceinthecourse offixingbreaksinDNA.
PGC: Primordialgermcell,akindofstemcellthatwillenabledevelopmentof spermcellsoreggcellsintheadultorganism.
PGD: Preimplantationgeneticdiagnosis,agenetictestperformedonaparticular geneatanearlystageofembryogenesisbeforeinsertingtheembryointoa wombviaIVF.
PGS: Preimplantationgenomicscreen,geneticanalysisoftheentiregenomeofan earlystageembryobeforeIVFtransferintoawomb.
Abbreviations xv
RNA: Ribonucleicacid,akindofbiomoleculethatcancontainheritableinformation(asforRNAviruses),serveasanintermediateinthetransmissionof heritableinformationinthecourseofproducingproteins(asformRNA),or functionasabioactivecomponentofcellstoinfluenceexpressionofgenesor othercellularactivities(suchasguidingCas9proteinstogenomiclocations, inthecaseofguideRNAs).
RNAi: Ribonucleicacidinterference,anexperimentaltechniquethatenablesa researchertoinhibittheexpressionofagene.
SCNT: Somaticcellnucleartransfer,akeyexperimentalprocedureusedtoclone mammalsthatinvolvesinsertionofthecellnucleusandDNAfromabody cellsuchasaskincellintoanenucleatedeggcell.
TARE: Toxin-antidoterecessiveembryogenedrive,aparticulartypeofgenetically engineeredselfishgeneticelementthatiscapableofincreasingitsabundance inthegenomesofapopulationfromonegenerationtothenext.
UV: Ultravioletlight,aformofelectromagneticradiationwithawavelength between10nmand400nm,thatisnotvisibletohumansbutcanbevisibletootherorganismswithappropriateshort-wavelength-sensitiveopsin proteins.
AbouttheAuthor
AsherD.CutterisaprofessorofEcologyandEvolutionaryBiologyattheUniversity ofToronto,Canada.AformerFulbrightScholar,CuttertrainedatTuftsUniversity, JamesCookUniversity,theUniversityofArizona,andtheUniversityofEdinburgh. Heauthoredthetextbook APrimerofMolecularPopulationGenetics,aswellasnearly 100scientificarticlesonthetopicsofgenomeevolution,populationgenetics,speciation,andthebiologyof Caenorhabditis nematoderoundworms.RaisedintheBoston, Massachusetts,area,CutterlivesinTorontowithhisfamily.
Natureintheraw,andcooked
WanderingthelongbeachoftheGoldCoastofAustraliaononesunnyJulyafternoon,a shiftoflightcaughtmyeyeinthethinskimofsurfonthesand.Leaningdown,Icouldn’t seemuch,justanovalshimmeragainstthetansand.WhenIcuppedmyhandstohold apalmfullofwaterandsandgrains,however,IdiscoveredsomethingthatI’dnever encounteredbefore:anutterlytransparentfish-shapedcreature.Aslongasmypalm waswide,itsflat-sidedbodysportedapigmenteddarkeyeoneachsideofitshead,and itwriggledsedatelybetweenmyfingers.Itwasabsolutelystunning.Ilaterlearnedthat thiscreatureiscalledaleptocephaluslarva,thejuvenileformofamarineeel.Itwas entirelytransparentandalive,andthewispybonesofitsskeletonwereonlyjustvisible asfaintpalecreases,asifencasedinthickwetcellophane.
Iwasamazed.Ihadonlyseensuchincredibletransparencyinbonelesscreatureslike jellyfishandnematoderoundworms.Or,inthechemicallypreservedfishinjarsthat IpreppedattheSmithsonianNationalMuseumofNaturalHistoryonesummerasa student.I’dclearedandstainedtheirdeadpiscinebodiestomakevisibletheirskeleton ofcrimsonbonesandceruleancartilage,courtesyofalizarinandalcianstains,theother tissuesrenderedtransparentfromarecipeofchemicalacidsandbasesandenzymes. Notonlyhadtheexistenceof living transparentvertebrates—asee-throughliveanimal withabackbone!—somehowevadedallofmypriorexperience,buttheunexpectedness oftheencounterinnatureinthepalmofmyhandwasamarvel(Figure 1.1).
Asabiologist,perhapsIshouldnotbesurprisedthatIamconstantlysurprised.I am,though.I’msurprisedandamazedbythemultitudeofshapes,sizes,colors,and behaviorsoforganismsthatIcomeacrossyearinandyearout,ofanimalsandplants andcrittersthatareneither.
Inthedaytodayofmybiologicalresearch,though,itisstringsofDNAthatIthink aboutmost.Ithinkaboutthespace-timeofgenetics,oftheswirlofthedoublehelixofa chromosomeasthesequenceofchemicallettersonitsrungsgoontomutateandevolve. IthinkabouthowtheDNAsequencesthattrailacrossmycomputerscreenencodethe ongoingtugofdistinctandancientforcesofevolution,arecordofwhathasevolved andofcluestowhereevolutionwillgonext.Ithinkaboutwhatexperimentswemight conducttoalterthoseDNAsequences,tocreatesomethingnewtotestthelimitsofour understandingofbiologicalprinciples.JustasIcan’thelpbutmarvelatanewpersonal discoveryonabeach,Imarvelattheprospectofmeldinggeneticengineeringwiththe forcesofevolution.
Figure1.1 Transparentleptocephaluslarvaofamarineeel(Queensland,Australia),oneofthe marvelsofthelivingworldthatalreadyexists. Photobytheauthor.
Inthelaboratory,wecancreateextraordinarycreatures.Inthelaboratory,wecan usegeneticengineeringtochangeacreature’sDNAsothatitexpressescharacteristicsit neverhadbeforeorthatnocreatureeverhadbefore.Inmylab,wehavewormslikenone foundinnature:wormswithgenesthatmakethemglowgreenorredoryellowwhen youshineaUVlampontothem.Thisfactteasesabiggeridea,anigglingquestionabout lifebeyondthelab.Wouldthegreatoutdoorsalsobenefitfromnewlyevolvedcreatures, populationsofnewandextraordinaryspecies,whatwemightcallhyperexoticspecies, producedwithevolutionaryengineeringtobesoremarkablethattheworldhadnever beforeseentheirlikeness?
Ididn’talwaysthinkabouttheDNAofgenomesandhowtomessaboutwiththem. Ioncewasalittlecountryboywhosatamongtheovergrownpokeweedinthesunny gardenofmyparents’backyard,smooshingtheirbrilliantberriesandfollowingtheslow trailsofinsectsalongtheirstems.IoncewasakidwhoroamedtheNewEnglandforest thatringedmychildhoodhomeattheendofadirtroad,snatchingbullfrogsinswampy
pondsandspyingthepinksac-likeflowersofladyslipperorchids—Cypripediumacaule boorishlyrenamedas“scrotumplants”—thatsproutedfromtherustyduffofpineneedlesinspring.EvenasIgotolder,throughuniversity,itwastheouterlivesintheliving worldthatIspenttimewith.Irubbedelbowswiththeplantsandanimalsofvernalpools andbogsandmangroveswamps,Ipeepedinonthesexlivesofbeetles,Isoughtoutthe signsoflifeinEocenefossilleavesandtheantsofAustraliantropicalrainforests.
AfterItransplantedmylifefromNewEnglandtoArizonaforatime,Ibegantolearn moreabouttheinnerlivesinthelivingworld.AttheendofthatfirstyearIlivedinTucson,1999,forthefirsttimeintheworld,thefirstanimalgotitsentiregenomesequenced. It’salittlesquiggleofacreatureknownasanematoderoundworm,oftenreferredtoas C.elegans.Whenyouwatchthroughtheeyepiecesofamicroscopeastheseminiature animalsswervesinuouslywithquietdetermination,youunderstandhowtheygottheir name: elegans derivesfromtheLatinfor elegant.Also,theyaretransparent.Iwashooked. Intheensuingyearsthathavenowturnedintodecades,they’vetaughtmehowDNA makesanorganismdevelopandhowDNAchanges,howtoengineergeneticchanges, andhowthosechangesmakeanorganismdevelopdifferentlyandbehavedifferently. Ididn’tgiveuponouterlivesthough.Understandingevolutionmeanspayingattentiontoboththeunseenandtheseen,bothDNAandthemagnificentdiversityofforms andspeciesallaroundus.ForaYankeeNewEnglander,theurbanincarnationofthe SonoranDesertofArizonashowedmeanalienlandscape.Ibeganapricklypeargarden inmyTucsonbackyard.Iexploitedtheastoundingbiologicalfeatthatmanyplants,and evensomeanimals,areabletodo:togrowanentirelynewindividualfromabrokenoffpieceofanother.Transplantingthetrimmingsofdiversevarietiesof Opuntia cactus thatIscavengedinthealleysaroundmyTucsonneighborhood—palegreenandpurple cladodepads,1 cladodescoveredinlongwhitishoryellowishspikes,enormousemeraldgreencladodesnearlydevoidofspines,cladodesnearlybrownwiththedenseclusters oftawnyprickles—theresoongrewaspinydisplayoflivingplant-paddlebiodiversity unlikeanythingI’dexperiencedinmyhometownoutsideofBoston.Theyweremyintownhomagetothesaguaro,those10-m-tall(33-foot-tall)botanicaliconsthatstoodin legionsthroughoutthefoothillsofthemountainsthatringedtheedgeofthecity.
Onsomeofmycacti,tinywhitefluffballspockedthesurface.Theylookedlikeclusters ofQ-tiptopsthat,atfirst,Ithoughtmightbeafungalinfection.Afterapokeproduced asmearofshockingpurple-redbrilliance,Irealizedthattheymustbecochinealbugs, acreatureI’dheardaboutonlyinstories.Cochineal Dactylopiuscoccus arethosemagnificentso-calledscaleinsects,parasitesof Opuntia pricklypear,thatproducecopious quantitiesofcarminicacidasadefenseagainstpredators.Humansharvestthatcarminic acidtomaketheintenseredcolorofcarminedye,a.k.a.naturalred#4oringredient E120.YoumightalsoknowcarminefromtheingredientlistofallmannerofFDAapprovedcosmeticsandfoodstuffs,fromlipsticktohotdogs,store-boughtstrawberry jamtotheredveneerofimitationcrab.
Doyoueverhappenuponnatureintherawtofindsomethingunexpectedinthe wild?Somethingbeautifulorinexplicable,itmightevenbesomethingtiny,something thatcompelsasmileoragasporalaugh?Thewovendetailofabird’snestdangling onabranch,theflashofthefirstfirefly’slightonasummerevening,fossilshellsspied
inarockonacliffside,atransparentanimalcaughtinthesurfonthebeach.Thereare truewondersinthisworldrightnow,everyminute.Theyhaveouterwondersandinner wonders,encodedinDNA.Perhapsweshould—orperhapsweshouldnot—gooutof ourwaytomakemorewondrousanimals.Couldwe?Howwouldwe?And,again, should we?
Evolution,geneticengineering,ecosystems,bioethics,andthestateoftheworld— we’llneedtosiftthroughallofthesethingstoanswerthosequestions.
1.1 Thenatureofchange
Theworldisawashinchange.Decadeoverdecade,theclimateacrosstheglobehas grownhigheraveragetemperaturesandgreaterextremesoftemperature.Comparedto preindustrialperiods,theairhas50%morecarbondioxide,andtheoceansare30% moreacidic,achievinglevelsunprecedentedoverthepast65millionyears.2 Wedid that.Entirespecieshavegoneextinctatsuchanastoundingratethatsomesaythat weareamidstthesixth-greatestmassextinctioneventthatourplanethaseverexperienced.Estimatesputtheworldonapaceofnearly1000speciesextinctionsaccumulating globallyeachyear,arate1000timeshigherthanitwasprehistorically.3 Population declinesandextinctionshitsometypesoforganisms,andsomeplaces,harderthan others.Invertebrates,largeanimals,amphibians,andtheIndo-Pacificareespecially hard-hit.4 Wedidthat,too.Andatthesametime,nonnative,invasivespeciesofanimalsandplantsarriveontheshores,islands,andwaterwaysofdistantlandsanddistant lakes,rivers,andseas.Thisspreadingoflifealongsidehumanmovementtakesaway lives,too,throughextinctionsmediatedbypredation,competition,andpathogenicity.5 Yes,wealsodidthat.Wehavecometodependonsomeofthosenonnativespecies, however,forfoodorothergoods.Theyfilltheagriculturalspacethatnowoccupies over41%oftheworld’sland.6 Human-manufacturedmaterial,frombuildingstosoda bottlestothemicroplasticflecksthatinfiltratethetissuesofseeminglypristinearcticwildlife,7 nowexceedthecombinedmassofalllivingthingsonplanetEarth,all 1.1trillionmetrictonsofit.8 Westupefyinglydidthat.Theseingloriousmarkersof changethatleavegeologicallyindelibletracksontheplanetarethehallmarksofthe Anthropoceneera.9
TheAnthropoceneisthehere-and-nowepochdefinedbyhumanity’sprofoundinfluenceonchangingtheshapeofthenaturalworld.I’velistedsomeofthedirectmaterial changes,mostofwhichyouhaveprobablyheardaboutfromnewsheadlines.Youcan relatetotheircausesorconsequencesinsomepartofyourday-to-daylife.Buttheyalso impactthenaturalworldindirectly:shiftsinwaysbothsubtleandprofoundtotheecologicalinteractionsthatorganismshavewithoneanotherandwiththeenvironmentsthey livein.Thesekindsofimpactscauseshiftstothenaturalselectionpressuresthatsculpt theevolutionofthosespeciesthatmanagetopersist,thatmanagetoevadeextinction. Humanscausedallthischangeinaboutonemilliondays.Theknock-oneffectson ecosystemsandevolutionofindividualspecies,however,willfollowthelawsoflifethat haveruledtheplanetforroughly3700millionyears.10 Humansnudge,orpunch,the
scalesofthewild,tippingbalances.Butalltheusualprocessesstillapplyinhownature responds:nutrientuptakeandrelease;predation;competitionbetweenorganismsfor resources,forsunandspaceandfoodandmates;under-the-hoodevolutionaryprocesses likemutationandnaturalselectionandgeneticdrift.Allthesethingsstilloperateinthe samefundamentalwayinresponsetoallthemanhandling.Withonepotentialexception. Mankind,orinthiscasewomankind,giventhe2020awardingoftherelevantNobel PrizeinChemistrytoEmmanuelleCharpentierandJenniferDoudna,11 hasdevised biotechnologywiththecapacityforhumanstobendthoselawsoflife.
Theideaofbendingthelawsoflifemaymakeyounervous.Theideaofcarvingthe DNAofwildorganismswithtoolsofgeneticengineeringmayeveninspireinyoua feelingofhorroratthehubris.Beforeindignityjumpsuptoohigh,however,takestock ofthefactthatwe’vebeenshapingtheDNAofanimalsandplantsandmicrobesfor millennia.Humancreationofdomesticatedanimalsandplantsaretheobviouscases— thehorseandhoganddog,theBrusselssproutandNashipearandfreestonepeach. Homosapiens isalsoanecosystemengineerparexcellence,meaningthatoursuccessesin makingtheworldmoretoourlikingalsomodifiestheworldfortheinnocentbystanders. OurAnthropoceneexploitspushtheforcesofevolution,drivingchangeinresponse tonewenvironmentalconditions,habitatperturbation,eliminationoffellowspecies,or creatingoverlapamongspeciesthathadneverbeforeencounteredoneanother.The evolutionaryresponsesintheoutdoorsare,perhaps,slowenoughforusindividuallyto acclimateto,toacceptasanewnormal.Thisacclimationishowshiftingbaselinesare born,fromonegenerationtothenext,casualacceptanceofwhatisprofoundlydifferent fromthegenerationbefore.
Whattodo?Oneoptionforcivilizationistocontinuetoacclimate.Thiskindof proposalisnotnecessarilyasapatheticasitmightseem.Forexample,byproactively establishinglargeregionsforrewilding,wecouldletecologicalandevolutionaryprocessesproceedinapassiveandnoninterventionistwaytopromotebiologicaldiversity andholisticecosystemfunctionality.ThenewsoutoftheUnitedKingdom,thesedays, seemschockfullofreportsofformerpasturelandlefttoseeditselfintoforestwithout thenibblingoflargeherdsofsheepandcattle.Itthenbecomesaquestionofpatience. Wehumans,however,arenotknownforourpatience.
AnotherwingofthoughtholdsthatthesymptomsofEarth’sillsaresodirethatthe curerequiresactivetreatment,notsimplebedrest.Thatis,humansoughttotakeaheavy handinestablishingfunctioningecosystems.Tohelpkeepthemostcatastrophiceffects ofrapidclimatechangeatbay,forexample,wecouldpartakeofsolargeoengineering— alteringatmosphericchemistrytoblockoutthesun—asatemporarychemicalparasol fortheplanet.Perhapsweevenoughttomodelnatureonthestructureandcompositionofecologicallandscapespriortowidespreadhumanimpacts,so-calledPleistocene trophicrewilding.Thisplancouldintroduceexistingspeciesintoenvironmentsinwhich theirecologicalanalogsareextinct,intentionallychangingthebiotawithacascadeof ecologicalconsequences.Thisplancouldalsointroducegeneticallyengineeredspecies, perhapsspeciesresurrected—asfortheso-calledde-extinctionofmammoths—oreven brand-newspeciesevolveddenovowiththeaidofbiotechnologicaltools.
