万物简史英文版_比尔·布莱森-第63章
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uld鈥檚。鈥�
when i asked fortey about it； he said： 鈥渨ell； it was very strange； quite shocking really；because gould鈥檚 portrayal of him had been so flattering。 i could only assume that simon wasembarrassed。 you know； science changes but books are permanent； and i suppose he regrettedbeing so irremediably associated with views that he no longer altogether held。 there was allthat stuff about 鈥榦h fuck； another phylum鈥櫋nd i expect he regretted being famous for that。鈥�
what happened was that the early cambrian fossils began to undergo a period of criticalreappraisal。 fortey and derek briggs鈥攐ne of the other principals in gould鈥檚 book鈥攗sed amethod known as cladistics to pare the various burgess fossils。 in simple terms； cladisticsconsists of organizing organisms on the basis of shared features。 fortey gives as an examplethe idea of paring a shrew and an elephant。 if you considered the elephant鈥檚 large size andstriking trunk you might conclude that it could have little in mon with a tiny； sniffingshrew。 but if you pared both of them with a lizard； you would see that the elephant andshrew were in fact built to much the same plan。 in essence； what fortey is saying is thatgould saw elephants and shrews where they saw mammals。 the burgess creatures； theybelieved； weren鈥檛 as strange and various as they appeared at first sight。 鈥渢hey were often nostranger than trilobites；鈥潯ortey says now。 鈥渋t is just that we have had a century or so to getused to trilobites。 familiarity； you know； breeds familiarity。鈥�
this wasn鈥檛； i should note； because of sloppiness or inattention。 interpreting the forms andrelationships of ancient animals on the basis of often distorted and fragmentary evidence isclearly a tricky business。 edward o。 wilson has noted that if you took selected species ofmodern insects and presented them as burgess…style fossils nobody would ever guess that theywere all from the same phylum； so different are their body plans。 also instrumental in helpingrevisions were the discoveries of two further early cambrian sites； one in greenland and onein china； plus more scattered finds； which between them yielded many additional and oftenbetter specimens。
the upshot is that the burgess fossils were found to be not so different after all。
hallucigenia； it turned out； had been reconstructed upside down。 its stilt…like legs wereactually spikes along its back。 peytoia； the weird creature that looked like a pineapple slice；was found to be not a distinct creature but merely part of a larger animal called anomalocaris。
many of the burgess specimens have now been assigned to living phyla鈥攋ust where walcottput them in the first place。 hallucigenia and some others are thought to be related toonychophora； a group of caterpillar…like animals。 others have been reclassified as precursorsof the modern annelids。 in fact； says fortey； 鈥渢here are relatively few cambrian designs thatare wholly novel。 more often they turn out to be just interesting elaborations of well…established designs。鈥潯s he wrote in his book life： 鈥渘one was as strange as a present daybarnacle； nor as grotesque as a queen termite。鈥�
so the burgess shale specimens weren鈥檛 so spectacular after all。 this made them； as forteyhas written； 鈥渘o less interesting； or odd； just more explicable。鈥潯heir weird body plans werejust a kind of youthful exuberance鈥攖he evolutionary equivalent； as it were； of spiked hair andtongue studs。 eventually the forms settled into a staid and stable middle age。
but that still left the enduring question of where all these animals had e from鈥攈owthey had suddenly appeared from out of nowhere。
alas； it turns out the cambrian explosion may not have been quite so explosive as all that。
the cambrian animals； it is now thought； were probably there all along； but were just toosmall to see。 once again it was trilobites that provided the clue鈥攊n particular that seeminglymystifying appearance of different types of trilobite in widely scattered locations around theglobe； all at more or less the same time。
on the face of it； the sudden appearance of lots of fully formed but varied creatures wouldseem to enhance the miraculousness of the cambrian outburst； but in fact it did the opposite。
it is one thing to have one well…formed creature like a trilobite burst forth in isolation鈥攖hatreally is a wonder鈥攂ut to have many of them； all distinct but clearly related； turning upsimultaneously in the fossil record in places as far apart as china and new york clearlysuggests that we are missing a big part of their history。 there could be no stronger evidencethat they simply had to have a forebear鈥攕ome grandfather species that started the line in amuch earlier past。
and the reason we haven鈥檛 found these earlier species； it is now thought； is that they weretoo tiny to be preserved。 says fortey： 鈥渋t isn鈥檛 necessary to be big to be a perfectlyfunctioning； plex organism。 the sea swarms with tiny arthropods today that have left nofossil record。鈥潯e cites the little copepod； which numbers in the trillions in modern seas andclusters in shoals large enough to turn vast areas of the ocean black； and yet our totalknowledge of its ancestry is a single specimen found in the body of an ancient fossilized fish。
鈥渢he cambrian explosion； if that鈥檚 the word for it； probably was more an increase in sizethan a sudden appearance of new body types；鈥潯ortey says。 鈥渁nd it could have happened quiteswiftly； so in that sense i suppose it was an explosion。鈥潯he idea is that just as mammalsbided their time for a hundred million years until the dinosaurs cleared off and then seeminglyburst forth in profusion all over the planet； so too perhaps the arthropods and other triploblastswaited in semimicroscopic anonymity for the dominant ediacaran organisms to have theirday。 says fortey： 鈥渨e know that mammals increased in size quite dramatically after thedinosaurs went鈥攖hough when i say quite abruptly i of course mean it in a geological sense。
we鈥檙e still talking millions of years。鈥�
incidentally； reginald sprigg did eventually get a measure of overdue credit。 one of themain early genera； spriggina； was named in his honor； as were several species； and the wholebecame known as the ediacaran fauna after the hills through which he had searched。 by thistime； however； sprigg鈥檚 fossil…hunting days were long over。 after leaving geology he foundeda successful oil pany and eventually retired to an estate in his beloved flinders range；where he created a wildlife reserve。 he died in 1994 a rich man。
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22 GOOD…BYE TO ALL THAT
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when you consider it from a human perspective； and clearly it would be difficult forus to do otherwise； life is an odd thing。 it couldn鈥檛 wait to get going； but then； having gottengoing； it seemed in very little hurry to move on。
consider the lichen。 lichens are just about the hardiest visible organisms on earth； butamong the least ambitious。 they will grow happily enough in a sunny churchyard； but theyparticularly thrive in environments where no other organism would go鈥攐n blowymountaintops and arctic wastes； wherever there is little but rock and rain and cold； and almostno petition。 in areas of antarctica where virtually nothing else will grow； you can findvast expanses of lichen鈥攆our hundred types of them鈥攁dhering devotedly to every wind…whipped rock。
for a long time； people couldn鈥檛 understand how they did it。 because lichens grew on barerock without evident nourishment or the production of seeds； many people鈥攅ducatedpeople鈥攂elieved they were stones caught in the process of being plants。 鈥渟pontaneously；inorganic stone bees living plant！鈥潯ejoiced one observer； a dr。 homschuch； in 1819。
closer inspection showed that lichens were more interesting than magical。 they are in facta partnership between fungi and algae。 the fungi excrete acids that dissolve the surface of therock； freeing minerals that the algae convert into food sufficient to sustain both。 it is not avery exciting arrangement； but it is a conspicuously successful one。 the world has more thantwenty thousand species of lichens。
like most things that thrive in harsh environments； lichens are slow…growing。 it may take alichen more than half a century to attain the dimensions of a shirt button。 those the size ofdinner plates； writes david attenborough； are therefore 鈥渓ikely to be hundreds if notthousands of years old。鈥潯t would be hard to imagine a less fulfilling existence。 鈥渢hey simplyexist；鈥潯ttenborough adds； 鈥渢estifying to the moving fact that life even at its simplest leveloccurs； apparently； just for its own sake。鈥�
it is easy to overlook this thought that life just is。 as humans we are inclined to feel that lifemust have a point。 we have plans and aspirations and desires。 we want to take constantadvantage of all the intoxicating existence we鈥檝e been endowed with。 but what鈥檚 life to alichen？ yet its impulse to exist； to be； is every bit as strong as ours鈥攁rguably even stronger。
if i were told that i had to spend decades being a furry growth on a rock in the woods； ibelieve i would lose the will to go on。 lichens don鈥檛。 like virtually all living things； they willsuffer any hardship； endure any insult； for a moment鈥檚 additional existence。 life； in short； justwants to be。 but鈥攁nd here鈥檚 an interesting point鈥攆or the most part it doesn鈥檛 want to bemuch。
this is perhaps a little odd because life has had plenty of time to develop ambitions。 if youimagine the 4；500…billion…odd years of earth鈥檚 history pressed into a normal earthly day；then life begins very early； about 4a。m。； with the rise of the first simple； single…celled organisms； but then advances no further for the next sixteen hours。 not until almost 8：30 inthe evening； with the day five…sixths over； has earth anything to show the universe but arestless skin of microbes。 then； finally； the first sea plants appear； followed twenty minuteslater by the first jellyfish and the enigmatic ediacaran fauna first seen by reginald sprigg inaustralia。 at 9：04p。m。 trilobites swim onto the scene； followed more or less immediately bythe shapely creatures of the burgess shale。 just before 10p。m。 plants begin to pop up on theland。 soon after； with less than two hours left in the day； the first land creatures follow。
thanks to ten minutes or so of balmy weather； by 10：24 the earth is covered in the greatcarboniferous forests whose residues give us all our coal； and the first winged insects areevident。 dinosaurs plod onto the scene just before 11p。m。 and hold sway for about three…quarters of an hour。 at twenty…one minutes to midnight they vanish and the age of mammalsbegins。 humans emerge one minute and seventeen seconds before midnight。 the whole of ourrecorded history； on this scale； would be no more than a few seconds； a single human lifetimebarely an instant。 throughout this greatly speeded…up day continents slide about and bangtogether at a clip that seems positively reckless。 mountains rise and melt away； ocean basinse and go； ice sheets advance and withdraw。 and throughout the whole； about three timesevery minute； somewhere on the planet there is a flashbulb pop of
