A Short History of Nearly Everything-第69章

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leaf　in　wet　mud；　or　depose　without　exposure　to　oxygen；permitting　the　molecules　in　its　bones　and　hard　parts　（and　very　occasionally　softer　parts）　to　bereplaced　by　dissolved　minerals；　creating　a　petrified　copy　of　the　original。　then　as　thesediments　in　which　the　fossil　lies　are　carelessly　pressed　and　folded　and　pushed　about　byearth’s　processes；　the　fossil　must　somehow　maintain　an　identifiable　shape。　finally；　but　aboveall；　after　tens　of　millions　or　perhaps　hundreds　of　millions　of　years　hidden　away；　it　must　befound　and　recognized　as　something　worth　keeping。

only　about　one　bone　in　a　billion；　it　is　thought；　ever　bees　fossilized。　if　that　is　so；　itmeans　that　the　plete　fossil　legacy　of　all　the　americans　alive　today—that’s　270　millionpeople　with　206　bones　each—will　only　be　about　fifty　bones；　one　quarter　of　a　pleteskeleton。　that’s　not　to　say　of　course　that　any　of　these　bones　will　actually　be　found。　bearing　inmind　that　they　can　be　buried　anywhere　within　an　area　of　slightly　over　3。6　million　squaremiles；　little　of　which　will　ever　be　turned　over；　much　less　examined；　it　would　be　something　ofa　miracle　if　they　were。　fossils　are　in　every　sense　vanishingly　rare。　most　of　what　has　lived　onearth　has　left　behind　no　record　at　all。　it　has　been　estimated　that　less　than　one　species　in　tenthousand　has　made　it　into　the　fossil　record。　that　in　itself　is　a　stunningly　infinitesimalproportion。　however；　if　you　accept　the　mon　estimate　that　the　earth　has　produced　30billion　species　of　creature　in　its　time　and　richard　leakey　and　roger　lewin’s　statement　（inthe　sixth　extinction　）　that　there　are　250；000　species　of　creature　in　the　fossil　record；　thatreduces　the　proportion　to　just　one　in　120；000。　either　way；　what　we　possess　is　the　merestsampling　of　all　the　life　that　earth　has　spawned。

moreover；　the　record　we　do　have　is　hopelessly　skewed。　most　land　animals；　of　course；　don’tdie　in　sediments。　they　drop　in　the　open　and　are　eaten　or　left　to　rot　or　weather　down　tonothing。　the　fossil　record　consequently　is　almost　absurdly　biased　in　favor　of　marine　creatures。

about　95　percent　of　all　the　fossils　we　possess　are　of　animals　that　once　lived　under　water；mostly　in　shallow　seas。

i　mention　all　this　to　explain　why　on　a　gray　day　in　february　i　went　to　the　natural　historymuseum　in　london　to　meet　a　cheerful；　vaguely　rumpled；　very　likeable　paleontologist　namedrichard　fortey。

fortey　knows　an　awful　lot　about　an　awful　lot。　he　is　the　author　of　a　wry；　splendid　bookcalled　life：　an　unauthorised　biography；　which　covers　the　whole　pageant　of　animate　creation。

but　his　first　love　is　a　type　of　marine　creature　called　trilobites　that　once　teemed　in　ordovicianseas　but　haven’t　existed　for　a　long　time　except　in　fossilized　form。　all　shared　a　basic　body　planof　three　parts；　or　lobes—head；　tail；　thorax—from　which　es　the　name。　fortey　found　hisfirst　when　he　was　a　boy　clambering　over　rocks　at　st。　david’s　bay　in　wales。　he　was　hookedfor　life。

he　took　me　to　a　gallery　of　tall　metal　cupboards。　each　cupboard　was　filled　with　shallowdrawers；　and　each　drawer　was　filled　with　stony　trilobites—twenty　thousand　specimens　in　all。

“it　seems　like　a　big　number；”　he　agreed；　“but　you　have　to　remember　that　millions　uponmillions　of　trilobites　lived　for　millions　upon　millions　of　years　in　ancient　seas；　so　twentythousand　isn’t　a　huge　number。　and　most　of　these　are　only　partial　specimens。　finding　aplete　trilobite　fossil　is　still　a　big　moment　for　a　paleontologist。”

trilobites　first　appeared—fully　formed；　seemingly　from　nowhere—about　540　million　yearsago；　near　the　start　of　the　great　outburst　of　plex　life　popularly　known　as　the　cambrianexplosion；　and　then　vanished；　along　with　a　great　deal　else；　in　the　great　and　still　mysteriouspermian　extinction　300；000　or　so　centuries　later。　as　with　all　extinct　creatures；　there　is　anatural　temptation　to　regard　them　as　failures；　but　in　fact　they　were　among　the　most　successfulanimals　ever　to　live。　their　reign　ran　for　300　million　years—twice　the　span　of　dinosaurs；which　were　themselves　one　of　history’s　great　survivors。　humans；　fortey　points　out；　havesurvived　so　far　for　one…half　of　1　percent　as　long。

with　so　much　time　at　their　disposal；　the　trilobites　proliferated　prodigiously。　most　remainedsmall；　about　the　size　of　modern　beetles；　but　some　grew　to　be　as　big　as　platters。　altogetherthey　formed　at　least　five　thousand　genera　and　sixty　thousand　species—though　more　turn　upall　the　time。　fortey　had　recently　been　at　a　conference　in　south　america　where　he　wasapproached　by　an　academic　from　a　small　provincial　university　in　argentina。　“she　had　a　boxthat　was　full　of　interesting　things—trilobites　that　had　never　been　seen　before　in　southamerica；　or　indeed　anywhere；　and　a　great　deal　else。　she　had　no　research　facilities　to　studythem　and　no　funds　to　look　for　more。　huge　parts　of　the　world　are　still　unexplored。”

“in　terms　of　trilobites？”

“no；　in　terms　of　everything。”

throughout　the　nineteenth　century；　trilobites　were　almost　the　only　known　forms　of　earlyplex　life；　and　for　that　reason　were　assiduously　collected　and　studied。　the　big　mysteryabout　them　was　their　sudden　appearance。　even　now；　as　fortey　says；　it　can　be　startling　to　go　tothe　right　formation　of　rocks　and　to　work　your　way　upward　through　the　eons　finding　no　visiblelife　at　all；　and　then　suddenly　“a　whole　profallotaspis　or　elenellus　as　big　as　a　crab　will　popinto　your　waiting　hands。”　these　were　creatures　with　limbs；　gills；　nervous　systems；　probingantennae；　“a　brain　of　sorts；”　in　fortey’s　words；　and　the　strangest　eyes　ever　seen。　made　ofcalcite　rods；　the　same　stuff　that　forms　limestone；　they　constituted　the　earliest　visual　systemsknown。　more　than　this；　the　earliest　trilobites　didn’t　consist　of　just　one　venturesome　speciesbut　dozens；　and　didn’t　appear　in　one　or　two　locations　but　all　over。　many　thinking　people　inthe　nineteenth　century　saw　this　as　proof　of　god’s　handiwork　and　refutation　of　darwin’sevolutionary　ideals。　if　evolution　proceeded　slowly；　they　asked；　then　how　did　he　account　forthis　sudden　appearance　of　plex；　fully　formed　creatures？　the　fact　is；　he　couldn’t。

and　so　matters　seemed　destined　to　remain　forever　until　one　day　in　1909；　three　months　shyof　the　fiftieth　anniversary　of　the　publication　of　darwin’s　on　the　origin　of　species　；　when　apaleontologist　named　charles　doolittle　walcott　made　an　extraordinary　find　in　the　canadianrockies。

walcott　was　born　in　1850　and　grew　up　near　utica；　new　york；　in　a　family　of　modest　means；which　became　more　modest　still　with　the　sudden　death　of　his　father　when　walcott　was　aninfant。　as　a　boy　walcott　discovered　that　he　had　a　knack　for　finding　fossils；　particularlytrilobites；　and　built　up　a　collection　of　sufficient　distinction　that　it　was　bought　by　louisagassiz　for　his　museum　at　harvard　for　a　small　fortune—about　70；000　in　today’s　money。

although　he　had　barely　a　high　school　education　and　was　self　taught　in　the　sciences；　walcottbecame　a　leading　authority　on　trilobites　and　was　the　first　person　to　establish　that　trilobiteswere　arthropods；　the　group　that　includes　modern　insects　and　crustaceans。

in　1879　he　took　a　job　as　a　field　researcher　with　the　newly　formed　united　states　geologicalsurvey　and　served　with　such　distinction　that　within　fifteen　years　he　had　risen　to　be　its　head。　in1907　he　was　appointed　secretary　of　the　smithsonian　institution；　where　he　remained　until　hisdeath　in　1927。　despite　his　administrative　obligations；　he　continued　to　do　fieldwork　and　towrite　prolifically。　“his　books　fill　a　library　shelf；”　according　to　fortey。　not　incidentally；　hewas　also　a　founding　director　of　the　national　advisory　mittee　for　aeronautics；　whicheventually　became　the　national　aeronautics　and　space　agency；　or　nasa；　and　thus　canrightly　be　considered　the　grandfather　of　the　space　age。

but　what　he　is　remembered　for　now　is　an　astute　but　lucky　find　in　british　columbia；　highabove　the　little　town　of　field；　in　the　late　summer　of　1909。　the　customary　version　of　the　storyis　that　walcott；　acpanied　by　his　wife；　was　riding　on　horseback　on　a　mountain　trail　beneaththe　spot　called　the　burgess　ridge　when　his　wife’s　horse　slipped　on　loose　stones。　dismountingto　assist　her；　walcott　discovered　that　the　horse　had　turned　a　slab　of　shale　that　contained　fossilcrustaceans　of　an　especially　ancient　and　unusual　type。　snow　was　falling—winter　es　earlyto　the　canadian　rockies—so　they　didn’t　linger；　but　the　next　year　at　the　first　opportunitywalcott　returned　to　the　spot。　tracing　the　presumed　route　of　the　rocks’　slide；　he　climbed　750feet　to　near　the　mountain’s　summit。　there；　8；000　feet　above　sea　level；　he　found　a　shaleoutcrop；　about　the　length　of　a　city　block；　containing　an　unrivaled　array　of　fossils　from　soonafter　the　moment　when　plex　life　burst　forth　in　dazzling　profusion—the　famous　cambrianexplosion。　walcott　had　found；　in　effect；　the　holy　grail　of　paleontology。　the　outcrop　becameknown　as　the　burgess　shale；　and　for　a　long　time　it　provided　“our　sole　vista　upon　the　inceptionof　modern　life　in　all　its　fullness；”　as　the　late　stephen　jay　gould　recorded　in　his　popular　bookwonderful　life　。

gould；　ever　scrupulous；　discovered　from　reading　walcott’s　diaries　that　the　story　of　theburgess　shale’s　discovery　appears　to　have　been　somewhat　embroidered—walcott　makes　nomention　of　a　slipping　horse　or　falling　snow—but　there　is　no　disputin