按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
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鈥檚 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鈥攚inter es earlyto the canadian rockies鈥攕o they didn鈥檛 linger； but the next year at the first opportunitywalcott returned to the spot。 tracing the presumed route of the rocks鈥櫋lide； he climbed 750feet to near the mountain鈥檚 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鈥攖he 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 鈥渙ur sole vista upon the inceptionof modern life in all its fullness；鈥潯s the late stephen jay gould recorded in his popular bookwonderful life 。
gould； ever scrupulous； discovered from reading walcott鈥檚 diaries that the story of theburgess shale鈥檚 discovery appears to have been somewhat embroidered鈥攚alcott makes nomention of a slipping horse or falling snow鈥攂ut there is no disputing that it was anextraordinary find。
it is almost impossible for us whose time on earth is limited to a breezy few decades toappreciate how remote in time from us the cambrian outburst was。 if you could fly backwardsinto the past at the rate of one year per second； it would take you about half an hour to reachthe time of christ； and a little over three weeks to get back to the beginnings of human life。
but it would take you twenty years to reach the dawn of the cambrian period。 it was； in otherwords； an extremely long time ago； and the world was a very different place。
for one thing； 500…million…plus years ago when the burgess shale was formed it wasn鈥檛 atthe top of a mountain but at the foot of one。 specifically it was a shallow ocean basin at thebottom of a steep cliff。 the seas of that time teemed with life； but normally the animals left norecord because they were soft…bodied and decayed upon dying。 but at burgess the cliffcollapsed； and the creatures below； entombed in a mudslide； were pressed like flowers in abook； their features preserved in wondrous detail。
in annual summer trips from 1910 to 1925 （by which time he was seventy…five years old）；walcott excavated tens of thousands of specimens （gould says 80；000； the normallyunimpeachable fact checkers of national georgraphic say 60；000）； which he brought back towashington for further study。 in both sheer numbers and diversity the collection wasunparalleled。 some of the burgess fossils had shells； many others did not。 some were sighted；others blind。 the variety was enormous； consisting of 140 species by one count。 鈥渢he burgessshale included a range of disparity in anatomical designs never again equaled； and notmatched today by all the creatures in the world鈥檚 oceans；鈥潯ould wrote。
unfortunately； according to gould； walcott failed to discern the significance of what hehad found。 鈥渟natching defeat from the jaws of victory；鈥潯ould wrote in another work； eightlittle piggies； 鈥渨alcott then proceeded to misinterpret these magnificent fossils in the deepestpossible way。鈥潯e placed them into modern groups； making them ancestral to today鈥檚 worms；jellyfish； and other creatures； and thus failed to appreciate their distinctness。 鈥渦nder such aninterpretation；鈥潯ould sighed； 鈥渓ife began in primordial simplicity and moved inexorably；predictably onward to more and better。鈥�
walcott died in 1927 and the burgess fossils were largely forgotten。 for nearly half acentury they stayed shut away in drawers in the american museum of natural history inwashington； seldom consulted and never questioned。 then in 1973 a graduate student fromcambridge university named simon conway morris paid a visit to the collection。 he wasastonished by what he found。 the fossils were far more varied and magnificent than walcotthad indicated in his writings。 in taxonomy the category that describes the basic body plans ofall organisms is the phylum； and here； conway morris concluded； were drawer after drawer ofsuch anatomical singularities鈥攁ll amazingly and unaccountably unrecognized by the manwho had found them。
with his supervisor； harry whittington； and fellow graduate student derek briggs； conwaymorris spent the next several years making a systematic revision of the entire collection； andcranking out one exciting monograph after another as discovery piled upon discovery。 manyof the creatures employed body plans that were not simply unlike anything seen before orsince； but were bizarrely different。 one； opabinia； had five eyes and a nozzle…like snout withclaws on the end。 another； a disc…shaped being called peytoia； looked almost ically like apineapple slice。 a third had evidently tottered about on rows of stilt…like legs； and was so oddthat they named it hallucigenia。 there was so much unrecognized novelty in the collectionthat at one point upon opening a new drawer conway morris famously was heard to mutter；鈥渙h fuck； not another phylum。鈥�
the english team鈥檚 revisions showed that the cambrian had been a time of unparalleledinnovation and experimentation in body designs。 for almost four billion years life haddawdled along without any detectable ambitions in the direction of plexity； and thensuddenly； in the space of just five or ten million years； it had created all the basic bodydesigns still in use today。 name a creature； from a nematode worm to cameron diaz； and theyall use architecture first created in the cambrian party。
what was most surprising； however； was that there were so many body designs that hadfailed to make the cut； so to speak； and left no descendants。 altogether； according to gould； atleast fifteen and perhaps as many as twenty of the burgess animals belonged to no recognizedphylum。 （the number soon grew in some popular accounts to as many as one hundred鈥攆armore than the cambridge scientists ever actually claimed。） 鈥渢he history of life；鈥潯rote gould；鈥渋s a story of massive removal followed by differentiation within a few surviving stocks； notthe conventional tale of steadily increasing excellence； plexity； and diversity。鈥�
evolutionary success； it appeared； was a lottery。
one creature thatdid manage to slip through； a small wormlike being called pikaiagracilens； was found to have a primitive spinal column； making it the earliest known ancestorof all later vertebrates； including us。pikaia were by no means abundant among the burgessfossils； so goodness knows how close they may have e to extinction。 gould； in a famousquotation； leaves no doubt that he sees our lineal success as a fortunate fluke： 鈥渨ind back thetape of life to the early days of the burgess shale； let it play again from an identical startingpoint； and the chance bees vanishingly small that anything like human intelligence wouldgrace the replay。鈥�
gould鈥檚 book was published in 1989 to general critical acclaim and was a great mercialsuccess。 what wasn鈥檛 generally known was that many scientists didn鈥檛 agree with gould鈥檚conclusions at all； and that it was all soon to get very ugly。 in the context of the cambrian；鈥渆xplosion鈥潯ould soon have more to do with modern tempers than ancient physiologicalfacts。
in fact； we now know； plex organisms existed at least a hundred million years beforethe cambrian。 we should have known a whole lot sooner。 nearly forty years after walcottmade his discovery in canada； on the other side of the planet in australia； a young geologistnamed reginald sprigg found something even older and in its way just as remarkable。
in 1946 sprigg was a young assistant government geologist for the state of south australiawhen he was sent to make a survey of abandoned mines in the ediacaran hills of the flindersrange； an expanse of baking outback some three hundred miles north of adelaide。 the ideawas to see if there were any old mines that might be profitably reworked using newertechnologies； so he wasn鈥檛 studying surface rocks at all； still less fossils。 but one day whileeating his lunch； sprigg idly overturned a hunk of sandstone and was surprised鈥攖o put itmildly鈥攖o see that the rock鈥檚 surface was covered in delicate fossils； rather like theimpressions leaves make in mud。 these rocks predated the cambrian explosion。 he waslooking at the dawn of visible life。
sprigg submitted a paper to nature ； but it was turned down。 he read it instead at the nextannual meeting of the australian and new zealand association for the advancement ofscience； but it failed to find favor with the association鈥檚 head； who said the ediacaran imprints were merely 鈥渇ortuitous inorganic markings鈥濃�攑atterns made by wind or rain ortides； but not living b