Geological Contemporaneity and Persistent Types of Life.docx
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Geological Contemporaneity and Persistent Types of Life.docx
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GeologicalContemporaneityandPersistentTypesofLife
GeologicalContemporaneityandPersistentTypesofLifebyThomasH.HuxleyMERCHANTSoccasionallygothroughawholesome,thoughtroublesomeandnotalwayssatisfactory,processwhichtheyterm"takingstock."Afteralltheexcitementofspeculation,thepleasureofgain,andthepainofloss,thetradermakesuphismindtofacefactsandtolearntheexactquantityandqualityofhissolidandreliablepossessions.
Themanofsciencedoeswellsometimestoimitatethisprocedure;and,forgettingforthetimetheimportanceofhisownsmallwinnings,tore-examinethecommonstockintrade,sothathemaymakesurehowfarthestockofbullioninthecellar--onthefaithofwhoseexistencesomuchpaperhasbeencirculating--isreallythesolidgoldoftruth.
TheAnniversaryMeetingoftheGeologicalSocietyseemstobeanoccasionwellsuitedforanundertakingofthiskind--foraninquiry,infact,intothenatureandvalueofthepresentresultsofpaleontologicalinvestigation;andthemoreso,asallthosewhohavepaidcloseattentiontothelatemultitudinousdiscussionsinwhichpaleontologyisimplicated,musthavefelttheurgentnecessityofsomesuchscrutiny.
Firstinorder,asthemostdefiniteandunquestionableofalltheresultsofpaleontology,mustbementionedtheimmenseextensionandimpulsegiventobotany,zoology,andcomparativeanatomy,bytheinvestigationoffossilremains.Indeed,themassofbiologicalfactshasbeensogreatlyincreased,andtherangeofbiologicalspeculationhasbeensovastlywidened,bytheresearchesofthegeologistandpaleontologist,thatitistobefearedtherearenaturalistsinexistencewholookupongeologyasBrindleyregardedrivers."Rivers,"saidthegreatengineer,"weremadetofeedcanals";andgeology,someseemtothink,wassolelycreatedtoadvancecomparativeanatomy.
Weresuchathoughtjustifiable,itcouldhardlyexpecttobereceivedwithfavourbythisassembly.Butitisnotjustifiable.Yourfavouritesciencehasherowngreataimsindependentofallothers;andif,notwithstandinghersteadydevotiontoherownprogress,shecanscattersuchrichalmsamonghersisters,itshouldberememberedthathercharityisofthesortthatdoesnotimpoverish,but"blessethhimthatgivesandhimthattakes."Regardthematteraswewill,however,thefactsremain.Nearly40,000speciesofanimalsandplantshavebeenaddedtotheSystemaNaturaebypaleontologicresearch.Thisisalivingpopulationequivalenttothatofanewcontinentinmerenumber;equivalenttothatofanewhemisphere,ifwetakeintoaccountthesmallpopulationofinsectsasyetfoundfossil,andthelargeproportionandpeculiarorganizationofmanyoftheVertebrata.
But,beyondthis,itisperhapsnottoomuchtosaythat,exceptforthenecessityofinterpretingpaleontologicfacts,thelawsofdistributionwouldhavereceivedlesscarefulstudy;whilefewcomparativeanatomists(andthosenotofthefirstorder)wouldhavebeeninducedbymereloveofdetail,assuch,tostudytheminutiaeofosteology,wereitnotthatinsuchminutiaelietheonlykeystothemostinterestingriddlesofferedbytheextinctanimalworld.
Theseassuredlyaregreatandsolidgains.Surelyitismatterfornosmallcongratulationthatinhalfacentury(forpaleontology,thoughitdawnedearlier,cameintofulldayonlywithCuvier)asubordinatebranchofbiologyshouldhavedoubledthevalueandtheinterestofthewholegroupofsciencestowhichitbelongs.
Butthisisnotall.Alliedwithgeology,paleontologyhasestablishedtwolawsofinestimableimportance:
thefirst,thatoneandthesameareaoftheearth'ssurfacehasbeensuccessivelyoccupiedbyverydifferentkindsoflivingbeings;thesecond,thattheorderofsuccessionestablishedinonelocalityholdsgood,approximately,inall.
Thefirstoftheselawsisuniversalandirreversible;thesecondisaninductionfromavastnumberofobservations,thoughitmaypossibly,andevenprobably,havetoadmitofexceptions.Asaconsequenceofthesecondlaw,itfollowsthatapeculiarrelationfrequentlysubsistsbetweenseriesofstrata,containingorganicremains,indifferentlocalities.Theseriesresembleoneanother,notonlyinvirtueofageneralresemblanceoftheorganicremainsinthetwo,butalsoinvirtueofaresemblanceintheorderandcharacteroftheserialsuccessionineach.Thereisaresemblanceofarrangement;sothattheseparatetermsofeachseries,aswellasthewholeseries,exhibitacorrespondence.
Successionimpliestime;thelowermembersofaseriesofsedimentaryrocksarecertainlyolderthantheupper;andwhenthenotionofagewasonceintroducedastheequivalentofsuccession,itwasnowonderthatcorrespondenceinsuccessioncametobelookeduponasacorrespondenceinage,or"contemporaneity."And,indeed,solongasrelativeageonlyisspokenof,correspondenceinsuccession'is'
correspondenceinage;itis'relative'contemporaneity.
Butitwouldhavebeenverymuchbetterforgeologyifsolooseandambiguousawordas"contemporaneous"hadbeenexcludedfromherterminology,andif,initsstead,sometermexpressingsimilarityofserialrelation,andexcludingthenotionoftimealtogether,hadbeenemployedtodenotecorrespondenceinpositionintwoormoreseriesofstrata.
Inanatomy,wheresuchcorrespondenceofpositionhasconstantlytobespokenof,itisdenotedbytheword"homology"anditsderivatives;andforGeology(whichafterallisonlytheanatomyandphysiologyoftheearth)itmightbewelltoinventsomesingleword,suchas"homotaxis"(similarityoforder),inordertoexpressanessentiallysimilaridea.This,however,hasnotbeendone,andmostprobablytheinquirywillatoncebemade--Towhatendburdensciencewithanewandstrangeterminplaceofoneold,familiar,andpartofourcommonlanguage?
Thereplytothisquestionwillbecomeobviousastheinquiryintotheresultsofpaleontologyispushedfurther.
Thosewhosebusinessitistoacquaintthemselvesspeciallywiththeworksofpaleontologists,infact,willbefullyawarethatveryfew,ifany,wouldrestsatisfiedwithsuchastatementoftheconclusionsoftheirbranchofbiologyasthatwhichhasjustbeengiven.
Ourstandardrepertoriesofpaleontologyprofesstoteachusfarhigherthings--todisclosetheentiresuccessionoflivingformsuponthesurfaceoftheglobe;totellusofawhollydifferentdistributionofclimaticconditionsinancienttimes;torevealthecharacterofthefirstofalllivingexistences;andtotraceoutthelawofprogressfromthemtous.
Itmaynotbeunprofitabletobestowontheseprofessionsasomewhatmorecriticalexaminationthantheyhavehithertoreceived,inordertoascertainhowfartheyrestonanirrefragablebasis;orwhether,afterall,itmightnotbewellforpaleontologiststolearnalittlemorecarefullythatscientific"arsartium,"theartofsaying"Idon'tknow."Andtothisendletusdefinesomewhatmoreexactlytheextentofthesepretensionsofpaleontology.
EveryoneisawarethatProfessorBronn's'Untersuchungen'andProfessorPictet's'TraitedePaleontologie'areworksofstandardauthority,familiarlyconsultedbyeveryworkingpaleontologist.Itisdesirabletospeakoftheseexcellentbooks,andoftheirdistinguishedauthors,withtheutmostrespect,andinatoneasfaraspossibleremovedfromcarpingcriticism;indeed,iftheyarespeciallycitedinthisplace,itismerelyinjustificationoftheassertionthatthefollowingpropositions,whichmaybefoundimplicitly,orexplicitly,intheworksinquestion,areregardedbythemassofpaleontologistsandgeologists,notonlyontheContinentbutinthiscountry,asexpressingsomeofthebest-establishedresultsofpaleontology.
Thus:
--
Animalsandplantsbegantheirexistencetogether,notlongafterthecommencementofthedepositionofthesedimentaryrocks;andthensucceededoneanother,insuchamanner,thattotallydistinctfaunaeandfloraeoccupiedthewholesurfaceoftheearth,oneaftertheother,andduringdistinctepochsoftime.
Ageologicalformationisthesumofallthestratadepositedoverthewholesurfaceoftheearthduringoneoftheseepochs:
ageologicalfaunaorfloraisthesumofallthespeciesofanimalsorplantswhichoccupiedthewholesurfaceoftheglobe,duringoneoftheseepochs.
Thepopulationoftheearth'ssurfacewasatfirstverysimilarinallparts,andonlyfromthemiddleoftheTertiaryepochonwards,begantoshowadistinctdistributioninzones.
Theconstitutionoftheoriginalpopulation,aswellasthenumericalproportionsofitsmembers,indicatesawarmerand,onthewhole,somewhattropicalclimate,whichremainedtolerablyequablethroughouttheyear.Thesubsequentdistributionoflivingbeingsinzonesistheresultofagradualloweringofthegeneraltemperature,whichfirstbegantobefeltatthepoles.
Itisnotnowproposedtoinquirewhetherthesedoctrinesaretrueorfalse;buttodirectyourattentiontoamuchsimplerthoughveryessentialpreliminaryquestion--Whatistheirlogicalbasis?
whatarethefundamentalassumptionsuponwhichtheyalllogicallydepend?
andwhatistheevidenceonwhichthosefundamentalpropositionsdemandourassent?
Theseassumptionsaretwo:
thefirst,thatthecommencementofthegeologicalrecordiscoevalwiththecommencementoflifeontheglobe;thesecond,thatgeologicalcontemporaneityisthesamethingaschronologicalsynchrony.Withoutthefirstoftheseassumptionstherewouldofcoursebenogroundforanystatementrespectingthecommencementoflife;withoutthesecond,alltheotherstatementscited,everyoneofwhichimpliesaknowledgeofth
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