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cient 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—just 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； “there are relatively few cambrian designs thatare wholly novel。 more often they turn out to be just interesting elaborations of well…established designs。” as he wrote in his book life： “none was as strange as a present daybarnacle； nor as grotesque as a queen termite。”
so the burgess shale specimens weren’t so spectacular after all。 this made them； as forteyhas written； “no less interesting； or odd； just more explicable。” their weird body plans werejust a kind of youthful exuberance—the 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—howthey 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—in 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—thatreally is a wonder—but 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—some grandfather species that started the line in amuch earlier past。
and the reason we haven’t found these earlier species； it is now thought； is that they weretoo tiny to be preserved。 says fortey： “it isn’t necessary to be big to be a perfectlyfunctioning； plex organism。 the sea swarms with tiny arthropods today that have left nofossil record。” he 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。
“the cambrian explosion； if that’s the word for it； probably was more an increase in sizethan a sudden appearance of new body types；” fortey says。 “and it could have happened quiteswiftly； so in that sense i suppose it was an explosion。” the 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： “we know that mammals increased in size quite dramatically after thedinosaurs went—though when i say quite abruptly i of course mean it in a geological sense。
we’re still talking millions of years。”
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’s 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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22GOOD…BYE TO ALL THAT
。^生。网
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’t 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—on 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—four hundred types of them—adhering devotedly to every wind…whipped rock。
for a long time； people couldn’t understand how they did it。 because lichens grew on barerock without evident nourishment or the production of seeds； many people—educatedpeople—believed they were stones caught in the process of being plants。 “spontaneously；inorganic stone bees living plant！” rejoiced 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 “likely to be hundreds if notthousands of years old。” it would be hard to imagine a less fulfilling existence。 “they simplyexist；” attenborough adds； “testifying to the moving fact that life even at its simplest leveloccurs； apparently； just for its own sake。”
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