Preface
Theaimofthisbookistodiscussthephenomenonoflife,includingits originandevolution(andalsoincludinghumanculturalevolution)against thebackgroundofthermodynamics,statisticalmechanicsandinformation theory.Thesecondlawofthermodynamicsstatesthattheentropy(disorder)oftheuniversealwaysincreases.Theseemingcontradictionbetween thesecondlawofthermodynamicsandthehighdegreeoforderandcomplexityproducedbylivingorganismswillbeacentralthemeofthebook. Thisapparentcontradictionhasitsresolutionintheinformationcontent oftheGibbsfreeenergywhichisconstantlyenteringthebiospherefrom outsidesources,aswillbediscussedindetailinChapter4.
Thebookbeginswithasketchofthehistoryofevolutionarythought andresearchnotonlyduringCharlesDarwin’slifetime,butalsobeforeand afterhim.Amongthepioneersofevolutionwhoseworkwillbediscussed areAristotle,Condorcet,Linnaeus,ErasmusDarwin,Lamarck,andLyell. TheylaidthefoundationsuponwhichCharlesDarwinbuilthistheory.
AfterCharlesDarwin’sdeathin1882,thetheoryofevolutioncontinuedtodevelopandcontinuedtobestrengthenedbynewlydiscoveredfacts. ModernmolecularbiologyandDNAtechnologyhaveallowedustoconstructevolutionaryfamilytreesinafarmoreprecisewaythanDarwinand hiscontemporariescoulddoonthebasisofmorphology.Datafromcomparativesequencingofmacromoleculeshave,onthewhole,confirmedthe19th centurypictureofevolution;buttheyhavealsosuppliedmuchknowledge whichwasnotavailabletotheearlypioneersofevolutionarytheory.
Darwinvisualizedevolutionastakingplacethroughnaturalselection actingonsmallinheritablevariationsintheindividualsofaspecies;butwe nowknowthatvariationscansometimesbesuddenandlarge—through mutationsofthetypestudiedbydeVriesandMuller,orthroughthestill moredrasticmechanismofsymbiosisandgeneticfusion.
Darwinspeculatedontheoriginoflife,buthedeliberatelyomitted discussionofthissubjectfromhispublications.However,inthelastletter whichheisknowntohavedictatedandsigned,hewrote:“...theprinciple oflifewillhereafterbeshowntobeapartorconsequenceofsomegeneral law.”Inourowntime,researcherssuchasA.I.Oparin,HeraldUrey,Stanley Miller,MelvinCalvin.SydneyFox,LeslieOrgel,CarlSagan,Manfred Eigen,ChristiandeDuve,ErwinSchr¨odinger,ClaudeShannon,andStuart Kaufmanhavebeguntouncoverthisgenerallaw.
Inthepicturethathasbeguntoemergefromtheworkoftheseresearchers,theearthoriginallyhadanatmospherefromwhichmolecular oxygenwasalmostentirelyabsent.Energysources,suchasunderseahydrothermalvents,ultravioletlight,volcanism,radioactivedecay,lightning flashes,andmeteoricimpacts,convertedthemoleculesoftheearth’sprimitiveoceanandatmosphereintoaminoacids,nucleotides,andotherbuilding blocksoflivingorganisms.Energy-richmolecules,suchasH2S,FeS,H2, phosphateesters,pyrophosphates,thioestersandHCNwerealsoproduced. Sincenolivingorganismswerepresent,andsincemolecularoxygenwas absentfromtheearlyatmosphere,theenergy-richmoleculeswerenotdegradedimmediately,andtheywerepresentinmoderateconcentrationsin theprimitiveocean.
Onethenvisualizesaneraof“chemicalDarwinism”,inwhichautocatalyticsystemscompetedforthesupplyofprecursorsandenergy-rich molecules.Theseautocatalyticsystems(i.e.systemsofmoleculeswhich catalysedthesynthesisofthemselves)canbethoughtofastheprecursorsoflife.Theynotonly“ate”theenergy-richmoleculespresentinthe earlyocean;theyalsoreproduced;andtheycompetedwitheachotherin acompletelyDarwinianway,randomvariationsinthedirectionofgreater efficiencybeingselectedandpropagated.
Anextremelyinterestingaspectofthepicturejustdiscussedisthespecialroleoftheenergy-richmolecules.Theyplayaspecialrolebecause theprocessofmolecularDarwinismatfirstsightseemstobeviolatingthe secondlawofthermodynamics—creatingorderoutofdisorder,whenaccordingtothesecondlaw,disorderoughttobecontinuallyincreasing.If wereflectfurtheralongtheselines,allformsoflifeseematfirstsighttobe creatingorderoutofdisorder,inviolationofthesecondlaw.
Livingorganismsareabletodothisbecausetheyarenotclosedsystems. Ifwelookatthe“fineprint”ofthesecondlawofthermodynamics,itsays thattheentropy(ordisorder)oftheuniversealwaysincreases—andof courseitdoes.Livingorganismsproduceorderwithinthemselvesandtheir
immediateenvironmentsbycreatingdisorderintheuniverseasawhole. Thedegradationoffoodintowasteproductsis,infact,theprocessthrough whichlifecreateslocalorderattheexpenseofglobaldisorder.Lifebuilds amazingdisplaysoflocalorder;butmeanwhile,thedisorderofthelarger systemincreases.Thelargersystemincludesthesun,theearth,andthe colddustcloudsofinterstellarspace.
Inthehypotheticalpictureoftheoriginoflifepresentedabove,the “food”moleculesaredegradedbytheautocatalystsintheprocessofordercreatingmolecularevolution.InChapter4ofthepresentbook,wewill focusontheentropyrelationshipsinthisprocess.ThestatisticalmechanicsofMaxwell,BoltzmannandGibbswillbecomparedwithinformation theory,asdevelopedbyClaudeShannonandothers.Itwillbeshownthat Gibbsfreeenergycarriesacontentofinformationandthatthe“thermodynamicinformation”obtainedbytheautocatalystsfromthefree-energy-rich moleculesintheprimitiveoceanwasthesourceoftheorderwhichdevelopedduringtheprocessofchemicalevolution.
Today,theearth’sgreatestsourceofthermodynamicinformationisthe floodoffreeenergywhichreachesusintheformofphotonsfromthesun.In Chapter4,aquantitativerelationshipwillbederivedconnectingtheenergy ofanabsorbedphotonanditsinformationcontent.Readerswhowishto skipthemathematicsinChapter4maydosowithoutlosingthethreadof theargument,providedthattheyarewillingtoacceptonfaiththemain resultofthederivations—thefactthatGibbsfreeenergycontainsthe thermodynamicformofinformation.
Itseemsprobablethatthermodynamicinformationderivedfromfree energywasthedrivingforcebehindtheoriginoflife.Itistodaythedriving forcebehindallformsoflife—behindthelocalorderwhichlifeisableto produce.Thisisthe“generallaw”whichDarwinguessedmightsomeday beshowntounderlietheprincipleoflife.Alloftheinformationcontained inthecomplex,beautiful,andstatisticallyunlikelystructureswhichareso characteristicoflivingorganismscanbeseenashavingbeendistilledfrom theenormousfloodofthermodynamicinformationwhichreachestheearth intheformofsunlight.
Wheredohumansfitintothispicture?Likeallotherformsoflifeon Earth,humanspassinformationfromonegenerationtothenext,coded intothebasesequencesoftheirDNA.However,humanshavedevelopeda second,highlyeffectivemodeofinformationtransmission—languageand culture.
Althoughlanguageandculturearenotuniquetoourspecies,theextent towhichtheyaredevelopedisuniqueonEarth.Thushumansaredistinguishedfromotherspeciesbyhavingtwomodesofevolutionarychange— geneticevolution,symbolizedbythelonginformation-containingDNA molecule,andculturalevolution,whichmightbesymbolizedbyabook oracomputerdiskette.
Ifwecomparethesetwomodesofevolution,wecanseethatgenetic evolutionisveryslow,whileculturalevolutionisextremelyrapid—and accelerating.Thehumangenomehaschangedverylittleduringthelast 40,000years;butduringthisperiod,culturalevolutionhasalteredourway oflifebeyondrecognition.Thereforehumannature,formedtofittheway oflifeofourhunter-gathererancestors,isnotentirelyappropriateforour presentwayoflife.Forexample,humannatureseemstocontainanelement ofwhatmightbecalled“tribalism”,whichdoesnotfitwellwiththemodern world’sinstantaneouscommunicationsandincreasinginterdependence.
Notonlydoesthegeneticevolutionofhumanslagbehindtheircultural evolution,butalsoculturalevolutionitselfhasarapidly-movingcomponentandaslowly-movingcomponentwhichlagsbehind,creatingtensions. Asweenterthe21stcentury,technologyisdevelopingwithphenomenal speed,whilesocialandpoliticalinstitutionschangefarmoreslowly.The disharmonythuscreatedrequiresstudyandthoughtifhumansocietyis nottobeshakentopiecesbytherapidityofscientificprogress.
Interestingly,informationtechnologyandbiotechnology,thetwomost rapidlydevelopingfields,arebecomingincreasinglylinked,eachfinding inspirationintheother.Biologistshavestudiedthemechanismofselfassemblyofsupramolecularstructuressuchascellmembranes,viruses, chloroplastsandmitochondria.Researchersinthefieldofnanoscienceare nowattemptingtousethisprincipleofsupramolecularorganization,observedinbiology,toreachanewdegreeofminiaturizationfortheswitches andmemorydevicesofinformationtechnology.Simulatedevolution,modelledafterbiologicalevolution,hasbeenusedtodevelopnewandunorthodoxcomputerhardwareandsoftware.Meanwhile,computersandautomationarebecomingmoreandmoreessentialtobiotechnology;andinfact manyuniversitiesnowhavedepartmentsdevotedtobioinformatics.Chapter7willtracethehistoryofinformationtechnology,whileChapter11will discussthewaysinwhichitismergingwithbiotechnology.
Thefinalchapterofthebooklooksatthefuturechallengesthathumanitywillfaceasaresultofscientiificandtechnicalprogress,combined witharapidlygrowingpopulation,andanincresingecologicalfootprint.
Acknowledgements
IamextremelygratefultoProfessorLawrenceS.Lerner,Dr.CindyLerner, ProfessorDudleyR.Herschbach,Dr.AnitaGoel,Dr.LuisEmilioBruni, andtomyson,JamesAveryfortheirgenerousadviceandhelp.ThecontributionsoftheLernershavebeenespeciallygreat.Theircarefulreading oftheentiremanuscriptandtheirmanydetailedsuggestionshavebeeninvaluable.MysonJamesreadseveralversionsofChapter4,andhisadvice wasagreathelpinwritingthefinalversionofthiscentralchapter.Healso helpedmetoimproveChapters7and8.Afewsectionsofthisbookare basedonnotesforacourseonScienceandSocietywhichIhavetaughtat theUniversityofCopenhagensince1989.Othersectionsdrawinspiration fromacourseonStatisticalMechanics,seenfromthestand-pointofinformationtheory,whichIhelpedtoteachsomeyearsearlier.TheStatistical MechanicscoursewasplannedbyAssociateProfessorKnudAndersen.I amalsogratefultoProfessorAlbertSzent-Gy¨orgyi,oneofthemostimportantpioneersofBioenergetics,formanyinspiringconversationsduringthe yearswhenIworkedinhislaboratoryatWoodsHole.FinallyIwouldlike tothankMr.HenningVibæk,whodrewthefigures.
Introductiontothethirdedition
IamgratefultotheWorldScientificPublishingCompanyforaskingmeto prepareathirdeditionofthisbook.Thishasallowedmetomakesome additionswhichIhopereaderswillenjoy:
ManyadditionshavebeenmadetoChapter7, InformationTechnology. Ihopethattheseadditionsreflecttherapidandconstantlyaccelerating progressbeingmadeinthisfield.withsuchnewdevelopmentsasWikipedia andeffectivesearchengines,suchasGoogle.
Achapterentitled Pathfinding hasbeenadded.Thischapterdiscusses thediscoveriesofthethreewinnersofthe2014NobelPrizeinPhysiologyor Medicine,ProfessorsJohnO’Keefe,May-BrittMoserandEdwardI.Moser. Theydiscoveredstructuresinthebrainsofmammalswhichareassociated withtheabilityoftheanimalstofindtheirway.JohnO’Keefediscovered “placecells”,whichfireonlywhenananimalwasataparticularplacein amaze.Theremainderofthechapterdiscussesotheranalogousexamples ofpathfinding
Thenextchapter,alsonewinthethirdedition,isentitled TheEvolutionofHumanLanguages.Theworld-famouslinguisticscientistNoam Chomskyhascorrectlypointedoutthathumanlanguagesarequalitatively
differentfromanimallanguages.Hehasalsoassertedthathumansacquiredtheirastonishinglinguisticabilitiesquitesuddenly.Thiscontradicts CharlesDarwin’sviewofevolutionarychangeastakingplaceveryslowly, throughmanysmallsteps,witheachsmallpositivestepbeingconfirmedby theforcesofnaturalselection.Nevertheless,becauseofProfessorChomsky’sstature,weneedtotakehisassertionofsuddenchangeseriously.
Inthenewchapteron TheEvolutionofHumanLanguages,weexplore thehypothesisthatasinglemutationcausedtheduplicationofthebrain structuresdiscoveredbythe2014NobelLaureates.Thenoneoftheduplicatestructurescouldhavebeenquicklymodifiedandusedtoexpand humanlinguisticabilities.Inhisdiscussionofserialhomologies,Darwin himselfnotedhowoftenentirestructuresseemtohavebeenduplicated.
Thishypothesisgivesusaplausibleexplanationforarelativelysuddenacquisitionbyhumansoftheirextraordinarylinguisticabilities,and itwouldjustify,inDarwinianterms,ProfessorChomsky’sseeminglyantiDarwinianassertion.
Anothernewchapterisentitled TheMechanismofCellDifferentiation Thischapterdiscussesthespecificmolecularmechanismsofcelldifferentiationinmulticellularorganisms.Weseeanalogiestothedecisiontrees discussedintheearlierchapteron Pathfinding.
Finally,thelastchapter, LookingTowardstheFuture,hasbeengreatly expanded,toreflecttheseriousproblemsthattheworldiscurrentlyfacing, forexamplethethreatofcatastrophicclimatechange.
PIONEERSOFEVOLUTIONARY THOUGHT
Aristotle
Aristotlewasbornin381B.C.,thesonofthecourtphysicianoftheking ofMacedon,andattheageofseventeenhewenttoAthenstostudy.He joinedPlato’sAcademyandworkedtherefortwentyyearsuntilPlatodied. AristotlethenlefttheAcademy,sayingthathedisapprovedoftheemphasis onmathematicsandtheoryandthedeclineofnaturalscience.Afterserving astutorforAlexanderofMacedon,hefoundedaschoolofhisowncalled theLyceum.AttheLyceum,hebuiltupacollectionofmanuscriptswhich resembledthelibraryofamodernuniversity.
Aristotlewasaverygreatorganizerofknowledge,andhiswritingsalmostformaone-manencyclopedia.Hisbestworkwasinbiology,where hestudiedandclassifiedmorethanfivehundredanimalspecies,manyof whichhealsodissected.InAristotle’sclassificationoflivingthings,he showsanawarenessoftheinterrelatednessofspecies.Thisinterrelatedness wasmuchlaterusedbyDarwinasevidenceforthetheoryofevolution. OnecannotreallysaythatAristotledevelopedatheoryofevolution,but hewasgropingtowardstheidea.Inhishistoryofanimals,hewrites:
“Natureproceedslittlebylittlefromlifelessthingstoanimallife,so thatitisimpossibletodetermineeithertheexactlineofdemarcation,or onwhichsideofthelineanintermediateformshouldlie.Thus,nextafter lifelessthingsintheupwardscalecomestheplant.Ofplants,onewilldiffer fromanotherastoitsapparentamountofvitality.Inaword,thewhole plantkingdom,whilstdevoidoflifeascomparedwiththeanimal,isyet endowedwithlifeascomparedwithothercorporealentities.Indeed,there isobservedinplantsacontinuousscaleofascenttowardstheanimal.”
Aristotle’sclassificationoflivingthings,startingatthebottomofthe scaleandgoingupward,isasfollows:inanimatematter,lowerplantsand
sponges,higherplants,jellyfish,zoophytesandascidians,molluscs,insects, jointedshellfish,octopusesandsquids,fishandreptiles,whales,landmammalsandman.TheacutenessofAristotle’sobservationandanalysiscan beseenfromthefactthatheclassifiedwhalesanddolphinsasmammals (wheretheybelong)ratherthanasfish(wheretheysuperficiallyseemto belong,andwheremanyancientwritersplacedthem).
AmongAristotle’sbiologicalwritings,thereappearsastatementthat clearlyforeshadowstheprincipleofnaturalselection,laterindependently discoveredbyDarwinandWallaceandfullydevelopedbyDarwin.Aristotlewrote:“Wheresoever,therefore...allpartsofonewholehappenedlike asiftheyweremadeforsomething,thesewerepreserved,havingbeenappropriatelyconstitutedbyaninternalspontaneity;andwheresoeverthings werenotthusconstituted,theyperished,andstillperish”.
OneofAristotle’simportantbiologicalstudieswashisembryological investigationofthedevelopingchick.Eversincehistime,thechickhas beentheclassicalobjectforembryologicalstudies.Healsostudiedthe four-chamberedstomachoftheruminantsandthedetailedanatomyofthe mammalianreproductivesystem.Heuseddiagramstoillustratecomplex anatomicalrelationships—animportantinnovationinteachingtechnique.
Averr¨oes
Aristotle’sevolutionaryideaswererevivedandextendedinthewritingsof theIslamicphilosopherAverr¨oes,1 wholivedinSpainfrom1126to1198. HiswritingshadagreatinfluenceonWesternthought.Averr¨oesshocked bothhisMoslemandhisChristianreadersbyhisthoughtfulcommentaries ontheworksofAristotle,inwhichhemaintainedthattheworldwasnot createdatadefiniteinstant,butthatitinsteadevolvedoveralongperiod oftime,andisstillevolving.
LikeAristotle,Averr¨oesseemstohavebeengropingtowardstheideas ofevolutionwhichwerelaterdevelopedingeologybyLyellandinbiology byDarwinandWallace.Muchofthescholasticphilosophywrittenatthe UniversityofParisduringthe13thcenturywasaimedatrefutingthedoctrinesofAverr¨oes;butnevertheless,hisideassurvivedandhelpedtoshape themodernpictureoftheworld.
1 AbulWalidMahommedIbnAchmed,IbnMahommedIbnRosched.
Themysteryoffossils
DuringthelifetimeofLeonardodaVinci(1452–1519)theexistenceoffossil shellsintherocksofhighmountainrangeswasrecognizedanddiscussed. “...theshellsinLombardyareatfourlevels”,Leonardowrote,“andthusit iseverywhere,havingbeenmadeatvarioustimes...Thestratifiedstones ofthemountainsarealllayersofclay,depositedoneabovetheotherbythe variousfloodsoftherivers.”Leonardohadnopatiencewiththeexplanation givenbysomeofhiscontemporaries,thattheshellshadbeencarriedto mountaintopsbythedelugedescribedintheBible.“Iftheshellshadbeen carriedbythemuddywatersofthedeluge”,hewrote,“theywouldhave beenmixedup,andseparatedfromeachotheramidstthemud,andnot inregularstepsandlayers.”NordidLeonardoagreewiththeopinionthat theshellssomehowgrewwithintherocks:“Suchanopinioncannotexist inabrainofmuchreason”,hewrote,“becauseherearetheyearsoftheir growth,numberedontheirshells,andtherearelargeandsmallonesto beseen,whichcouldnothavegrownwithoutfood,andcouldnothavefed withoutmotion...andheretheycouldnotmove.”
Leonardobelievedthatthefossilshellswereoncepartoflivingorganisms,thattheywereburiedinstrataunderwater,andmuchlaterliftedto thetopsofmountainsbygeologicalupheavals.Howeverhisacuteobservationshadlittleinfluenceontheopinionsofhiscontemporariesbecausethey appearamongthe4,000orsopagesofnoteswhichhewroteforhimselfbut neverpublished.
ItwaslefttotheDanishscientistNielsStensen(1638–1686)(usually knownbyhisLatinizedname,Steno)toindependentlyrediscoverandpopularizethecorrectinterpretationoffossilsandofrockstrata.Steno,who hadstudiedmedicineattheUniversityofLeiden,wasworkinginFlorence, wherehisanatomicalstudiesattractedtheattentionoftheGrandDuke ofTuscany,FerdenandII.Whenanenormoussharkwascaughtbylocal fishermen,theDukeorderedthatitsheadbebroughttoStenofordissection.TheDanishanatomistwasstruckbyshapeoftheshark’steeth,which remindedhimofcertaincuriouslyshapedstonescalledglossopetraethat weresometimesfoundembeddedinlargerrocks.Stenoconcludedthatthe similarityofformwasnotjustacoincidence,andthattheglossopetrae wereinfacttheteethofonce-livingsharkswhichhadbecomeembeddedin themuddysedimentsatthebottomoftheseaandgraduallychangedto stone.Stenousedthecorpusculartheoryofmatter,aforerunnerofatomic theory,toexplainhowthecompositionofthefossilscouldhavechanged
whiletheirformremainedconstant.Stenoalsoformulatedalawofstrata, whichstatesthatinthedepositionoflayersofsediment,laterconvertedto rock,theoldestlayersareatthebottom.
InEngland,thebrilliantandversatileexperimentalscientistRobert Hooke(1635–1703)addedtoSteno’scorrectinterpretationoffossilsby noticingthatsomefossilspeciesarenotrepresentedbyanylivingcounterparts.Heconcludedthat“therehavebeenmanyotherSpeciesofCreatures informerAges,ofwhichwecanfindnoneatpresent;andthat’tisnotunlikelyalsobutthattheremaybediversnewkindsnow,whichhavenot beenfromthebeginning.”
SimilarobservationsweremadebytheFrenchnaturalist,Georges-Louis Leclerc,ComtedeBuffon(1707–1788),whowrote:“Wehavemonuments takenfromthebosomoftheEarth,especiallyfromthebottomofcoaland slatemines,thatdemonstratetousthatsomeofthefishandplantsthat thesematerialscontaindonotbelongtospeciescurrentlyexisting.”Buffon’spositionaskeeperoftheJardinduRoi,theFrenchbotanicalgardens, allowedhimtimeforwriting,andwhileholdingthispostheproduceda 44-volumeencyclopediaofnaturalhistory.Inthisenormous,clearlywritten,andpopularwork,Buffonchallengedthetheologicaldoctrineswhich maintainedthatallspecieswerecreatedindependently,simultaneouslyand miraculously,6,000yearsago.Asevidencethatspecieschange,Buffon pointedtovestigialorgans,suchasthelateraltoesofthepig,whichmay havehadausefortheancestorsofthepig.Hethoughtthatthedonkey mightbeadegeneraterelativeofthehorse.Buffonbelievedtheearthto bemucholderthanthe6,000yearsallowedbytheBible,buthisestimate, 75,000years,greatlyunderestimatedthetrueageoftheearth.
ThegreatScottishgeologistJamesHutton(1726–1797)hadafarmore realisticpictureofthetrueageoftheearth.Huttonobservedthatsome rocksseemedtohavebeenproducedbythecompressionofsedimentslaid downunderwater,whileotherrocksappearedtohavehardenedafterpreviousmelting.Thusheclassifiedrocksasbeingeitherigneousorelsesedimentary.Hebelievedthefeaturesoftheearthtohavebeenproducedby theslowactionofwind,rain,earthquakesandotherforceswhichcanbe observedtoday,andthattheseforcesneveractedwithgreaterspeedthan theydonow.Thisimpliedthattheearthmustbeimmenselyold,and Huttonthoughtitsagetobealmostinfinite.Hebelievedthattheforces whichturnedseabedsintomountainrangesdrewtheirenergyfromthe heatoftheearth’smoltencore.TogetherwithSteno,Huttonisconsidered tobeoneofthefathersofmoderngeology.Hisuniformitarianprinciples,
andhisbeliefinthegreatageoftheearthwerelatergivenwidecirculation byCharlesDarwin’sfriendandmentor,SirCharlesLyell(1797–1875),and theypavedthewayforDarwin’sapplicationofuniformitarianismtobiology.Atthetimeofhisdeath,Huttonwasworkingonatheoryofbiological evolutionthroughnaturalselection,buthismanuscriptsonthissubject remainedunknownuntil1946
Condorcet
FurthercontributionstotheideaofevolutionweremadebytheFrench mathematicianandsocialphilosopherMarie-Jean-Antoine-NicolasCaritat, MarquisdeCondorcet,whowasbornin1743.In1765,whenhewasbarely 22yearsold,Condorcetpresentedan EssayontheIntegralCalculus to theAcademyofSciencesinParis.Theyear1785sawthepublicationof Condorcet’shighlyoriginalmathematicalwork, Essaisurl’applicationde l’analyse`alaprobabilit´edesdecisionsrendues`alapluralit´edesvoix, 2 in whichhepioneeredtheapplicationofthetheoryofprobabilitytothesocialsciences.Alater,muchenlarged,editionofthisbookextendedthe applicationstogamesofchance.
Condorcethadalsobeenoccupied,sinceearlychildhood,withtheidea ofhumanperfectibility.Hewasconvincedthattheprimarydutyofevery personistocontributeasmuchaspossibletothedevelopmentofmankind, andthatbymakingsuchacontribution,onecanalsoachievethegreatestpossiblepersonalhappiness.WhentheFrenchRevolutionbrokeoutin 1789,hesawitasanunprecedentedopportunitytodohispartinthecause ofprogress;andheenteredthearenawholeheartedly,eventuallybecomingPresidentoftheLegislativeAssembly,andoneofthechiefauthorsof theproclamationwhichdeclaredFrancetobearepublic.Unfortunately, Condorcetbecameabitterenemyofthepowerfulrevolutionarypolitician, Robespierre,andhewasforcedtogointohiding.
AlthoughRobespierre’sagentshadbeenunabletoarresthim,Condorcetwassentencedtotheguillotineinabsentia.Heknewthatinall probabilityhehadonlyafewweeksormonthstolive;andhebeganto writehislastthoughts,racingagainsttime.Condorcetreturnedtoaproject whichhehadbegunin1772,ahistoryoftheprogressofhumanculture, stretchingfromtheremotepasttothedistantfuture.Guessingthathe wouldnothavetimetocompletethefull-scaleworkhehadonceplanned,
2 EssayontheApplicationofAnalysistotheProbabilityofDecisionsTakenAccording toaPluralityofVotes.
hebeganasketchoroutline: Esquissed’untableauhistoriquedesprogr`es del’esprithumain. 3
Inhis Esquisse,Condorcetenthusiasticallyendorsedtheideaofinfinite humanperfectibilitywhichwascurrentamongthephilosophersofthe18th century;andheanticipatedmanyoftheevolutionaryideaswhichCharles Darwinlaterputforward.Hecomparedhumanswithanimals,andfound manycommontraits.AccordingtoCondorcet,animalsareabletothink, andeventothinkrationally,althoughtheirthoughtsareextremelysimple comparedwiththoseofhumans.Condorcetbelievedthathumanshistoricallybegantheirexistenceonthesamelevelasanimalsandgradually developedtotheirpresentstate.Sincethisevolutiontookplacehistorically, hereasoned,itisprobable,oreveninevitable,thatasimilarevolutionin thefuturewillbringmankindtoalevelofphysical,mentalandmoraldevelopmentwhichwillbeassuperiortoourownpresentstateaswearenow superiortoanimals.
Atthebeginningofhismanuscript,Condorcetstatedhisbelief“that naturehassetnoboundsontheimprovementofhumanfacilities;thatthe perfectibilityofmanisreallyindefinite;andthatitsprogressishenceforth independentofanypowertoarrestit,andhasnolimitexcepttheduration oftheglobeuponwhichnaturehasplacedus”.Hestatedalsothat“the moralgoodnessofmanisanecessaryresultofhisorganism;anditis,like allhisotherfacilities,capableofindefiniteimprovement.”
Liketheotherscientistsandphilosophersofhisperiod,CondorcetacceptedtheNewtonianideaofanorderlycosmosruledbynaturallawsto whichtherearenoexceptions.Heassertedthatthesamenaturallawsmust governhumanevolution,sincehumansarealsopartofnature.Againand again,Condorcetstressedthefundamentalsimilaritybetweenhumansand animals;andheregardedalllivingthingsasbelongingtothesamegreat family.(ItisperhapsthisinsightwhichmadeCondorcetsosensitiveto thefeelingsofanimalsthatheevenavoidedkillinginsects.)Toexplainthe presentdifferencesbetweenhumansandanimals,Condorcetmaintained, weneedonlyimaginegradualchanges,continuingoveranextremelylong periodoftime.Theselong-continuedsmallchangeshaveveryslowlyimprovedhumanmentalabilitiesandsocialorganization,sothatnow,atthe endofanimmenseintervaloftime,largedifferenceshaveappearedbetween ourselvesandlowerformsoflife.
3 SketchofanHistoricalPictureoftheProgressoftheHumanSpirit.
Condorcetregardedthefamilyastheoriginalsocialunit;andin Esquisse hecalledattentiontotheunusuallylongperiodofdependencywhich characterizesthegrowthandeducationofhumanoffspring.Thisprolonged childhoodisuniqueamonglivingbeings.Itisneededforthehighlevelof mentaldevelopmentofthehumanspecies;butitrequiresastablefamily structuretoprotecttheyoungduringtheirlongupbringing.Thus,accordingtoCondorcet,biologicalevolutionbroughtintoexistenceamoral precept,thesanctityofthefamily.
Similarly,Condorcetwrote,largerassociationsofhumanswouldhave beenimpossiblewithoutsomedegreeofaltruismandsensitivitytothesufferingofothersincorporatedintohumanbehavior,eitherasinstinctsoras moralpreceptsorboth;andthustheevolutionoforganizedsocietyentailed thedevelopmentofsensibilityandmorality.UnlikeRousseau,Condorcet didnotregardhumansinorganizedcivilizationsasdegradedandcorrupt comparedto“natural”man;insteadhesawcivilizedhumansasmoredevelopedthantheirprimitiveancestors.
Believingthatignoranceanderrorareresponsibleforvice,Condorcet discussedwhathebelievedtobethemainmistakesofcivilization.Among thesehenamedhereditarytransmissionofpower,inequalitybetweenmen andwomen,religiousbigotry,disease,war,slavery,economicinequality, andthedivisionofhumanityintomutuallyexclusivelinguisticgroups.Regardingdisease,Condorcetpredictedthattheprogressofmedicalscience wouldultimatelyabolishit.Also,hemaintainedthatsinceperfectibility (i.e.,evolution)operatesthroughoutthebiologicalworld,thereisnoreason whymankind’sphysicalstructuremightnotgraduallyimprove,withthe resultthathumanlifeintheremotefuturecouldbegreatlyprolonged.
Condorcetbelievedthattheintellectualandmoralfacilitiesofmanare capableofcontinuousandsteadyimprovement;andhethoughtthatone ofthemostimportantresultsofthisimprovementwouldbetheabolition ofwar.Ashumansbecomeenlightenedinthefuture(hebelieved)they willrecognizewarasanatrociousandunnecessarycauseofsuffering;and aspopulargovernmentsreplacehereditaryones,warsfoughtfordynasticreasonswilldisappear.Nexttovanishwillbewarsfoughtbecauseof conflictingcommercialinterests.Finally,theintroductionofauniversal languagethroughouttheworldandtheconstructionofperpetualconfederationsbetweennationswilleliminate,Condorcetpredicted,warsbasedon ethnicrivalries.
Withbetterlaws,socialandfinancialinequalitieswouldtendtobecome leveled.Tomakethesocialconditionsoftheworkingclassmoreequalto
thoseofthewealthy,Condorcetadvocatedasystemofinsurance(either privateorgovernmental)wherethesavingsofworkerswouldbeusedto providepensionsandtocareforwidowsandorphans.Also,sincesocialinequalityisrelatedtoinequalityofeducation,Condorcetadvocatedasystem ofuniversalpubliceducationsupportedbythestate.
Attheendofhis Esquisse,Condorcetwrotethatanypersonwhohas contributedtothebestofhisabilitytotheprogressofmankindbecomes immunetopersonaldisasterandsuffering.Heknowsthathumanprogress isinevitable,andcantakecomfortandcouragefromhisinnerpicture oftheepicmarchofmankind,throughhistory,towardsabetterfuture. EventuallyCondorcet’shiding-placewasdiscovered.Hefledindisguise, butwasarrestedafterafewdays;andhediedsoonafterwardsinhisprison cell.AfterCondorcet’sdeaththecurrentsofrevolutionarypoliticsshifted direction.Robespierre,theleaderoftheTerror,washimselfsoonarrested. TheexecutionofRobespierretookplaceonJuly25,1794,onlyafewmonths afterthedeathofCondorcet.
Condorcet’s Esquissed’untableauhistoriquedesprogr`esdel’esprith main waspublishedposthumouslyin1795.Inthepost-Thermidorreconstruction,theConventionvotedfundstohaveitprintedinalargeedition anddistributedthroughoutFrance,thusadoptingthe Esquisse asitsofficial manifesto.ThissmallbutpropheticbookistheoneforwhichCondorcetis nowchieflyremembered.Itwasdestinedtoestablishtheforminwhichthe eighteenth-centuryideaofprogresswasincorporatedintoWesternthought, anditprovokedRobertMalthustowrite AnEssayonthePrincipleofPopulation.Condorcet’sideasareimportantbecauseheconsideredthegenetic evolutionofplantsandanimalsandhumanculturalevolutiontobetwo partsofasingleprocess.
Linnaeus
Meanwhile,duringthe17thand18thcenturies,naturalistshadbeengatheringinformationonthousandsofspeciesofplantsandanimals.This huge,undigestedheapofinformationwasputintosomeorderbythegreat Swedishnaturalist,CarlvonLinn´e(1707–1778),whoisusuallycalledby hisLatinname,CarolusLinnaeus.
LinnaeuswasthesonofaSwedishpastor.Evenasayoungboy,hewas fondofbotany,andaftermedicalstudiesatLund,hebecamealecturer inbotanyattheUniversityofUppsala,nearStockholm.In1732,the25year-oldLinnaeuswasaskedbyhisuniversitytovisitLaplandtostudythe plantsinthatremotenorthernregionofSweden.
LinnaeustravelledfourthousandsixhundredmilesinLapland,andhe discoveredmorethanahundrednewplantspecies.In1735,hepublished hisfamousbook, SystemaNaturae,inwhichheintroducedamethodfor theclassificationofalllivingthings.
Linnaeusnotonlyarrangedcloselyrelatedspeciesintogenera,buthe alsogroupedrelatedgeneraintoclasses,andrelatedclassesintoorders. (LatertheFrenchnaturalistCuvier(1769–1832)extendedthissystemby groupingrelatedordersintophyla.)Linnaeusintroducedthebinomial nomenclature,stillusedtoday,inwhicheachplantoranimalisgivena namewhosesecondpartdenotesthespecieswhilethefirstpartdenotes thegenus.
Althoughhestartedalineofstudywhichledinevitablytothetheory ofevolution,Linnaeushimselfbelievedthatspeciesareimmutable.He adheredtothethen-conventionalviewthateachspecieshadbeenindependentlyandmiraculouslycreatedsixthousandyearsago,asdescribedinthe BookofGenesis.
Linnaeusdidnotattempttoexplainwhythedifferentspecieswithina genusresembleeachother,norwhycertaingeneraarerelatedandcanbe groupedintoclasses,etc.Itwasnotuntilacenturylaterthattheseresemblanceswereunderstoodastruefamilylikenesses,sothattheresemblance betweenacatandalioncametobeunderstoodintermsoftheirdescent fromacommonancestor.4
ErasmusDarwin
AmongtheardentadmirersofLinnaeuswasthebrilliantphysician-poet, ErasmusDarwin(1731–1802),whowasconsideredbyColeridgetohave“... agreaterrangeofknowledgethananyothermaninEurope”.Hewasalso thebestEnglishphysicianofhistime,andGeorgeIIIwishedtohavehim ashispersonaldoctor.However,Darwinpreferredtoliveinthenorthof EnglandratherthaninLondon,andherefusedtheposition.
In1789,ErasmusDarwinpublishedabookcalled TheBotanicGarden orTheLovesofthePlants.Itwasabookofbotanywritteninverse,and intheprefaceDarwinstatedthathispurposewas“...toinlistimagination underthebannerofscience...”andtocallthereader’sattentionto”the
4 LinnaeuswastoDarwinwhatKeplerwastoNewton.Kepleraccuratelydescribed themotionsofthesolarsystem,butitremainedforNewtontoexplaintheunderlying dynamicalmechanism.Similarly,Linnaeussetforthadescriptive“familytree”ofliving things,butDarwindiscoveredthedynamicmechanismthatunderliestheobservations.
immortalworksofthecelebratedSwedishnaturalist,Linnaeus”.Thisbook wasimmenselypopularatthetimewhenitwaswritten,butitwaslater satirizedbyPitt’sForeignMinister,Canning,whosebook TheLovesofthe Triangles ridiculedDarwin’spoeticstyle.
In1796ErasmusDarwinpublishedanotherbook,entitled Zoonomia,in whichheproposedatheoryofevolutionsimilartothatwhichhisgrandson,CharlesDarwin,waslatertomakefamous.“...Whenwethinkover thegreatchangesintroducedintovariousanimals”,Darwinwrote,“asin horses,whichwehaveexercisedfordifferentpurposesofstrengthandswiftness,carryingburthensorinrunningraces;orindogs,whichhavebeen cultivatedforstrengthandcourage,asthebull-dog;orforacutenessof hissenseofsmell,asinthehoundandspaniel;orfortheswiftnessofhis feet,asthegreyhound;orforhisswimminginthewater,orfordrawing snow-sledges,astherough-haireddogsofthenorth...andaddtothesethe greatchangeofshapeandcolorwhichwedailyseeproducedinsmaller animalsfromourdomesticationofthem,asrabbitsorpigeons;...whenwe revolveinourmindsthegreatsimilarityofstructurewhichobtainsinall thewarm-bloodedanimals,aswellasquadrupeds,birdsandamphibious animals,asinmankind,fromthemouseandthebattotheelephantand whale;weareledtoconcludethattheyhavealikebeenproducedfroma similarlivingfilament.”
“Woulditbetoobold”,ErasmusDarwinasked,“toimaginethatin thegreatlengthoftimesincetheearthbegantoexist,perhapsmillionsof agesbeforethecommencementofthehistoryofmankind—woulditbeto boldtoimaginethatallwarm-bloodedanimalshavearisenfromoneliving filament?”
Lamarck
InFrance,JeanBaptistePierreAntoinedeMonet,ChevalierdeLamarck (1744–1829),contributedimportantlytothedevelopmentofevolutionary ideas.AfteraperiodintheFrencharmy,fromwhichhewasforcedto retirebecauseofillness,Lamarckbecamebotanisttotheking,andlater ProfessorofInvertebrateZoologyattheMuseumofNaturalHistoryin Paris.Lamarckdeservestobecalledthefatherofinvertebratezoology. Linnaeushadexhaustedhisenergyonthevertebrates,andhehadleftthe invertebratesindisorder.TheirclassificationislargelyduetoLamarck: Hedifferentiatedtheeight-leggedarachnids,suchasspidersandscorpions, fromsix-leggedinsects;heestablishedthecategoryofcrustaceansforcrabs,
lobstersetc.;andheintroducedthecategoryofechinodermsforstarfish, sea-urchinsetc.Between1785and1822,Lamarckpublishedsevenhuge volumesofatreatiseentitled NaturalHistoryofInvertebrates.However,it isforhisbook ZoologicalPhilosophy,publishedin1809,thattheChevalier deLamarckischieflyrememberedtoday.
Inhis ZoologicalPhilosophy,Lamarckstatedhisbeliefthatthespecies withinagenusowetheirsimilaritytodescentfromacommonancestor. HewasthefirstprominentbiologistsincetheageofAristotletobelieve thatspeciesarenotimmutablebutthattheyhavechangedduringthelong historyoftheearth.
AlthoughLamarckdeservesmuchcreditasapioneerofevolutionary thought,hewasseriouslywrongaboutthemechanismofchange.Forexample,Lamarckbelievedthatthelongneckofthegiraffeevolvedbecause eachgiraffestretcheditsneckslightlyinanefforttoreachtheleaveson hightrees.Hebelievedthattheseslightly-stretchedneckscouldbeinherited,andthus,inthisway,overmanygenerations,thenecksofgiraffes hadgrownlongerandlonger.AlthoughLamarckwasrightinhisgeneral pictureofevolution,hewasmistakeninthedetailedmechanismwhichhe proposed,sincelaterexperimentsprovedconclusivelythat,ingeneral,acquiredcharacteristicscannotbeinherited.(Onemustsay“ingeneral”, becauseinthecaseofsymbiosisandgeneticfusion,acquiredcharacteristicsareinherited.Plasmidscontaininggeneticmaterialarealsofrequently exchangedbetweenbacteria.Furthermore,inhumanculturalevolution, innovationscanbepassedontofuturegenerations.Wewilldiscussthese Lamarckianmechanismsofevolutioninlaterchapters.)
ThedebatesbetweenCuvierandGeoffroySt.Hilaire
In1830,ayearafterthedeathofLamarck,afamousseriesofdebatestook placebetweenGeorgesLeopoldDagobert,BaronCuvier(1769–1832)and EtienneGeoffroySt.Hilaire(1772–1844).Thetwomen,bothprofessorsat theMuseeNationald’HistoireNaturelleinParis,wereclosefriendsandscientificcollaborators.However,theydifferedintheiropinions,especiallyon thequestionofwhethertheformofananimal’spartsledtotheirfunction, orwhetherthereversewastrue.Cuvieralmostsinglehandedlyfounded thedisciplineofvertebratepaleontology,andhefirmlyestablishedthefact thatextinctionshavetakenplace.However,hedidnotbelieveinevolution. In1828,Cuvierwrote:“Ifthereareresemblancesbetweentheorgansof fishesandthoseofothervertebrateclasses,itisonlyinsofarasthereare
resemblancesbetweentheirfunctions.”Inotherwords,functionproduces form.Cuvierdeniedthatsimilarityofformimplieddescentfromacommon ancestor.
St.Hilaire,ontheotherhand,consideredallvertebratestobemodificationsofasinglearchetype.Hemaintainedthatsimilarvestigialorgans andsimilaritiesinembryonicdevelopmentimplieddescentfromacommon ancestor.Hewasespeciallyinterestedinhomologies,thatis,caseswhere similarstructuresintwodifferentorganismsareusedfortwodifferentpurposes.In1829,St.Hilairewrote:“Animalshavenohabitsbutthosethat resultfromthestructureoftheirorgans:ifthelattervaries,therevaryin thesamemanneralltheirspringsofaction,alltheirfacilities,andalltheir actions.”
Theopposingviewpointsofthetwomenledtoafamousseriesofeight publicdebates,whichtookplacefromFebruarytoApril,1830.Although Cuvierwasthoughtbymostobserverstohavewonthedebates,St.Hilaire’s beliefinevolutioncontinued,asdidthefriendshipbetweenthetwonaturalists.In1832St.HilairepartiallyanticipatedDarwin’stheoryofevolution throughnaturalselection:“Theexternalworldisall-powerfulinalteration oftheformoforganizedbodies...”,hewrote,“These[modifications]are inherited,andtheyinfluencealltherestoftheorganizationoftheanimal, becauseifthesemodificationsleadtoinjuriouseffects,theanimalswhich exhibitthemperishandarereplacedbyothersofasomewhatdifferent form,aformchangedsoastobeadaptedtothenewenvironment.”
Suggestionsforfurtherreading
(1) P.J.Bowler, Evolution:TheHistoryofanIdea,UniversityofCalifornia Press,(1989).
(2) D.J.Putuyma, EvolutionaryBiology,SinauerAssociates,Sunderland Mass.,(1986).
(3) B.Glass,0.Temkin,andW.L.Strauss,eds., ForerunnersofDarwin: 1745-1859,JohnsHopkinsPress,Baltimore,(1959).
(4) R.Milner, TheEncyclopediaofEvolution,anOwlBook,HenryHolt andCompany,NewYork,(1990).
(5) T.A.Appel, TheCuvier-GeoffroyDebate:FrenchBiologyinthe DecadesbeforeDarwin,OxfordUniversityPress,(1987).
(6) P.J.Bowler, FossilsandProgress:PaleontologyandtheIdeaofProgressiveEvolutionintheNineteenthCentury,ScienceHistoryPublications, NewYork,(1976).
(7) H.Torrens, PresidentialAddress:MaryAnning(1799-1847)ofLyme; ’thegreatestfossilisttheworldeverknew’,BritishJournaloftheHistory ofScience, 28,257-284,(1995).
(8) P.Corsi, TheAgeofLamarck:EvolutionaryTheoriesinFrance,17901834,UniversityofCaliforniaPress,Berkeley,(1988).
(9) C.C.Gillispie, GenesisandGeology:AStudyintheRelationsofScientificThought,NaturalTheologyandSocialOpinioninGreatBritain, 1790-1850,HarvardUniversityPress,CambridgeMass.,(1951).
(10) M.McNeil, UndertheBannerofScience:ErasmusDarwinandhis Age,ManchesterUniversityPress,Manchester,(1987).
(11) L.G.Wilson, SirCharlesLyell’sScientificJournalsontheSpecies Question,YaleUniversityPress,NewHaven,(1970).
(12) M. ’Espinasse,RobertHooke,2nded.,U.ofCaliforniaPress,(1962).
(13) M.J.S.Rudwick, TheMeaningofFossils:EpisodesintheHistoryof Paleontology,2nded.,UniversityofChicagoPress,(1985).
(14) A.B.Adams, EternalQuest:TheStoryoftheGreatNaturalists,G.P. Putnam’sSons,NewYork,(1969).
(15) A.S.Packard, Lamarck,theFounderofEvolution:HisLifeandWork, Longmans,Green,andCo.,NewYork,(1901).
(16) C.Darwin, AnhistoricalsketchoftheprogressofopinionontheOrigin ofSpecies,previouslytothepublicationofthiswork,Appendedtothird andlatereditionsof OntheOriginofSpecies,(1861).
(17) L.Eiseley, Darwin’sCentury:EvolutionandtheMenwhoDiscovered It,Doubleday,NewYork,(1958).
(18) H.F.Osborne, FromtheGreekstoDarwin:TheDevelopmentofthe EvolutionIdeaThroughTwenty-FourCenturies,CharlesScribnerand Sons,NewYork,(1929).
