21 LIFE GOES ON

类别:文学名著 作者:比尔·布莱森 本章:21 LIFE GOES ON

    It ISN’t EASY to become a fossil. te of nearly all living organisms—over 99.9percent of to compost doo noto be put to use in some otem. t’s just t is. Even if you make it into t, t don’t get devoured, the chances of being fossilized are very small.

    In order to become a fossil, several t , you must die in tplace. Only about 15 percent of rocks can preserve fossils, so it’s no good keeling over on afuture site of granite. In practical terms t become buried in sediment,  mud, or decompose  exposure to oxygen,permitting ts bones and s (and very occasionally softer parts) to bereplaced by dissolved minerals, creating a petrified copy of ts in  someain an identifiable s aboveall, after tens of millions or per must befound and recognized as someth keeping.

    Only about one bone in a billion, it is t, ever becomes fossilized. If t is so, itmeans t te fossil legacy of all today—t’s 270 millionpeople  fifty bones, one quarter of a completeskeleton. t’s not to say of course t any of tually be found. Bearing inmind t tly over 3.6 million squaremiles, little of  of  imated t less tent into t in itself is a stunningly infinitesimalproportion.  timate t ture in its time and Ricatement (intinction ) t ture in treduces tion to just one in 120,000. Eit sampling of all t Earth has spawned.

    Moreover, t land animals, of course, don’tdie in sediments. ten or left to rot or onotly is almost absurdly biased in favor of marine creatures.

    About 95 percent of all t once lived under er,mostly in shallow seas.

    I mention all to explain o tural oryMuseum in London to meet a cologist namedRicey.

    Fortey kno about an a.  of animate creation.

    But  love is a type of marine creature called trilobites t once teemed in Ordovicianseas but  existed for a long time except in fossilized form. All ss, or lobes—ail, tey found  . David’s Bay in ales. he was hookedfor life.

    ook me to a gallery of tall metal cupboards. Eacony trilobites—ty thousand specimens in all.

    “It seems like a big number,”  you o remember t millions uponmillions of trilobites lived for millions upon millions of years in ancient seas, so tyt a  of tial specimens. Finding acomplete trilobite fossil is still a big moment for a paleontologist.”

    trilobites first appeared—fully formed, seemingly from noart of t outburst of complex life popularly kno deal else, in t and still mysteriousPermian extinction 300,000 or so centuries later. As inct creatures, tural temptation to regard t in fact t successfulanimals ever to live. tory’s great survivors. ey points out,  as long.

    itime at trilobites proliferated prodigiously. Most remainedsmall, about tles, but some greo be as big as platters. Altoget least five ty turn upall time. Fortey ly been at a conference in Souty in Argentina. “S eresting trilobites t  deal else. Sies to studyto look for more. s of till unexplored.”

    “In terms of trilobites?”

    “No, in terms of everything.”

    t teentury, trilobites  t reason ed and studied. teryabout tey says, it can be startling to go tot formation of rocks and to  all, and taspis or Elenellus as big as a crab o your ing ures ems, probingantennae, “a brain of sorts,” in Fortey’s rangest eyes ever seen. Made ofcalcite rods, tuff t forms limestone, tituted t visual systemskno trilobites didn’t consist of just one venturesome speciesbut dozens, and didn’t appear in one or tions but all over. Many teentury saation of Darionary ideals. If evolution proceeded slo fortures? t is, .

    And so matters seemed destined to remain forever until one day in 1909, tietion of Darologist named Ctle alcott made an extraordinary find in the CanadianRockies.

    alcott ica, Ne means,ill t . As a boy alcott discovered t icularlytrilobites, and built up a collection of sufficient distinction t it  $70,000 in today’s money.

    Altion and augtbecame a leading auty on trilobites and  person to establis trilobites includes modern insects and crustaceans.

    In 1879 ook a job as a field researced States GeologicalSurvey and served inction t een years o be its ed secretary of titution, ive obligations, inued to do fieldoe prolifically. “o Fortey. Not incidentally, or of tional Advisory Committee for Aeronautics, ional Aeronautics and Space Agency, or NASA, and tly be considered the space age.

    But e but lucky find in Britistle toe summer of 1909. tomary version of toryis t alcott, accompanied by ain trail beneat called tones. Dismountingto assist t discovered t turned a slab of s contained fossilcrustaceans of an especially ancient and unusual type. Snoer comes earlyto t linger, but t year at t opportunityalcott returned to t. tracing te of t to near tain’s summit. t above sea level, crop, about ty block, containing an unrivaled array of fossils from soonafter t t , tology. tcrop becameknoime it provided “our sole vista upon tionof modern life in all its fullness,” as te Stephen Jay Gould recorded in his popular bookonderful Life .

    Gould, ever scrupulous, discovered from reading alcott’s diaries t tory of to  embroidered—alcott makes nomention of a slipping  ting t it raordinary find.

    It is almost impossible for us ed to a breezy feoappreciate e in time from us tburst o t at te of one year per second, it ake you about o reacime of C, and a little over to get back to the beginnings of human life.

    But it ake you ty years to reac remely long time ago, and t place.

    For one t  attop of a mountain but at t of one. Specifically it tom of a steep cliff. t time teemed  normally t norecord because t-bodied and decayed upon dying. But at Burgess tures beloombed in a mudslide, ures preserved in ail.

    In annual summer trips from 1910 to 1925 (by t excavated tens of t cional Georgrap back toason for furtudy. In boty tion . Some ing of 140 species by one count. “ty in anatomical designs never again equaled, and notmatcoday by all tures in te.

    Unfortunately, according to Gould, alcott failed to discern t c from tory,” Gould e in anotLittle Piggies, “alcott to misinterpret t fossils in tpossible ral to today’s o appreciate tinctness. “Under sucerpretation,” Gould sigy and moved inexorably,predictably ono more and better.”

    alcott died in 1927 and tten. For nearly ury tayed s aural ory inason, seldom consulted and never questioned. te student fromCambridge University named Simon Con to tion. onis  tted in ings. In taxonomy tegory t describes ter draies—all amazingly and unaccountably unrecognized by them.

    ittington, and felloe student Derek Briggs, Con t several years making a systematic revision of tire collection, andcranking out one exciting monograper anotures employed body plans t  simply unlike anyt . One, Opabinia,  oia, looked almost comically like apineapple slice. A tly tottered about on roilt-like legs, and  t y in tiont at one point upon opening a neter,“O another phylum.”

    team’s revisions s time of unparalleledinnovation and experimentation in body designs. For almost four billion years life  any detectable ambitions in tion of complexity, and t five or ten million years, it ed all till in use today. Name a creature, from a nematode o Cameron Diaz, and tecture first created in ty.

    surprising,  t o make t, so to speak, and left no descendants. Altogeto Gould, atleast fifteen and pery of to no recognizedps to as many as one ists ever actually claimed.) “tory of life,” e Gould,“is a story of massive removal folloiation ocks, nottional tale of steadily increasing excellence, complexity, and diversity.”

    Evolutionary success, it appeared, tery.

    One creature tdid manage to slip to ive spinal column, making it t knoorof all later vertebrates, including us.Pikaia  among to extinction. Gould, in a famousquotation, leaves no doubt t unate fluke: “ind back tape of life to t it play again from an identical startingpoint, and t anytelligence he replay.”

    Gould’s book ical acclaim and  commercialsuccess.   generally kno many scientists didn’t agree  all, and t it o get very ugly. In text of to do empers t ps.

    In fact, ed at least a  sooner. Nearly forty years after alcottmade  in Australia, a young geologistnamed Reginald Sprigg found somets  as remarkable.

    In 1946 Sprigg ant government geologist for tate of Soutraliao make a survey of abandoned mines in tback some to see if t migably reec studying surface rocks at all, still less fossils. But one day o put itmildly—to see t te fossils, rated t the dawn of visible life.

    Sprigg submitted a paper to Nature , but it urned doead at tannual meeting of tralian and Neion for t ofScience, but it failed to find favor ion’s s uitous inorganic markings”—patterns made by ides, but not living beings.  yet entirely crusraveled to London andpresented o ternational Geological Congress, but failed to exciteeiterest or belief. Finally, for  of a better outlet, ransactions of ty of Soutralia. t  job andtook up oil exploration.

    Nine  years  later,  in  1957,  a  sc in trange fossil in it, similar toa modern sea pen and exactly like some of trying totell everyone about ever since. turned it in to a paleontologist at tyof Leicester,  at once as Precambrian. Young Mason got ure in treated as a precocious ill is in many books. the specimen wasnamed in his honor Chamia masoni.

    today some of Sprigg’s original Ediacaran specimens, along een  t time, canbe seen in a glass case in an upstairs room of tout and lovely Soutralian Museumin Adelaide, but t attract a great deal of attention. tely etcterns arerat and not terribly arresting to trained eye. tly small and disc-srailing ribbons. Fortey -bodiedoddities.”

    till very little agreement about old, no mouto take in and discivematerials, and no internal organs o process teysays, “most of t, like soft,structureless and inanimate flatfis t, tures ic, meaning t from tissue. ition of jellyfisoday are triploblastic.

    Some experts t animals at all, but more like plants or fungi. tinctions bet and animal are not als life fixed to a single spot and ing , and yet is ananimal. “o ts and animalsey. “t any rule t says you o bedemonstrably one or ther.”

    Nor is it agreed t tral to anytoday (except possibly some jellyfisies see t, a stab at complexity t didn’t take, possibly because tcompeted by ticated animals of theCambrian period.

    “today,” Fortey ten. “t tointerpret as any kind of ancestors of o follow.”

    t ultimately t terribly important to t of lifeon Earties believe t termination at t all tures (except tain jellyfiso move on to t parted ’s  in any case.

    As for t at once people began to questionterpretations and, in particular, Gould’s interpretation of terpretations. “From t tists  t Steve Gould ed, s delivery,” Fortey e in Life. tis putting it mildly.

    “If only Stepes!” barked telegrap tdoerarytour-de-force,” but accused Gould of engaging in a “grandiloquent and near-disingenuous”

    misrepresentation of ts by suggesting t tunned tological community. “t tacking—t evolution marcoward a pinnacle suc been believed for 50 years,” Dawkinsfumed.

    And yet t ly to which many general reviewers were drawn.

    One, ing in times Book Revie as a result ofGould’s book scientists “ some preconceptions t texamined for generations. tantly or entically, accepting t of nature as a product of orderly development.”

    But t directed at Gould arose from t many of aken or carelessly inflated. riting in tion, DatackedGould’s assertions t “evolution in t kind of process fromtoday” and expressed exasperation at Gould’s repeated suggestions t “tionary ‘experiment,’ evolutionary ‘trial and error,’ evolutionary ‘false starts.’ .

    . . It ile time al body plans’ ed.

    Noion just tinkers  new species!”

    Noting en t there are no new body plans—is picked up, Dawkins says:

    “It is as t an oak tree and remarked,  it stranget no major neo be at twig level.’ ”

    “It range time,” Fortey says no t somet  feelings really did runquite  I felt as if I ougo put a safety  on beforeing about t it did actually feel a bit like t.”

    Strangest of all artled many in tological community by rounding abruptly on Gouldin a book of ion. treated Gould “empt, evenloatey’s e later. “tion, unaory,  to (if not actuallysh) Gould’s.”

    ey about it,  range, quite srayal of tering. I could only assume t Simon , and I suppose tedbeing so irremediably associated  oget stuff about ‘o ted being famous for t.”

    to undergo a period of criticalreappraisal. Fortey and Derek Briggs—one of tics to compare terms, cladisticsconsists of organizing organisms on tures. Fortey gives as an examplet. If you considered t’s large size andstriking trunk you mig it could tle in common iny, sniffings if you compared bot t ands built to muc Fortey is saying is tGould sa as strange and various as t first sigen nostranger trilobites,” Fortey says no is just t o getused to trilobites. Familiarity, you knoy.”

    t, I se, because of sloppiness or inattention. Interpreting tions animals on ten distorted and fragmentary evidence isclearly a tricky business. Ed if you took selected species ofmodern insects and presented tyle fossils nobody  t are trumental in es, one in Greenland and onein Ctered finds, ional and oftenbetter specimens.

    t is t to be not so different after all.

    turned out, ructed upside dos stilt-like legs ually spikes along its back. Peytoia, ture t looked like a pineapple slice,o be not a distinct creature but merely part of a larger animal called Anomalocaris.

    Many of to living p  t place.  to be related toOnycerpillar-like animals. Ot, says Fortey, “tively feare urn out to be just interesting elaborations of ablise in range as a present daybarnacle, nor as grotesque as a queen termite.”

    So t so spectacular after all. teyten, “no less interesting, or odd, just more explicable.” t a kind of youtionary equivalent, as it uds. Eventually ttled into a staid and stable middle age.

    But t still left tion of w of nowhere.

    Alas, it turns out t e so explosive as all t.

    t is no,   toosmall to see. Once again it rilobites t provided ticular t seeminglymystifying appearance of different types of trilobite in tered locations around t more or less time.

    On t, ts of fully formed but varied creatures o enburst, but in fact it did te.

    It is one to ure like a trilobite burst fortion—treally is a  to inct but clearly related, turning upsimultaneously in t as Cs t  of tory. tronger evidencet to  started t.

    And t found t is no, is t too tiny to be preserved. Says Fortey: “It isn’t necessary to be big to be a perfectlyfunctioning, complex organism. tiny artoday t  nofossil record.” es ttle copepod, ers in so turn vast areas of t our totalknos ancestry is a single specimen found in t fossilized fish.

    “t’s t, probably ypes,” Fortey says. “And it could esly, so in t sense I suppose it  just as mammalsbided time for a il t fort, so too perriploblastsed in semimicroscopic anonymity for t Ediacaran organisms to ey: “e kno mammals increased in size quite dramatically after t—te abruptly I of course mean it in a geological sense.

    e’re still talking millions of years.”

    Incidentally, Reginald Sprigg did eventually get a measure of overdue credit. One of ter time, ing days er leaving geology ually retired to an estate in ed a wildlife reserve. he died in 1994 a rich man.


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