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suitable subject。 the moose； when shot； unfortunately lacked the imposing horns thatjefferson had specified； but sullivan thoughtfully included a rack of antlers from an elk orstag with the suggestion that these be attached instead。 who in france； after all； would know？
meanwhile in philadelphia—wistar’s city—naturalists had begun to assemble the bones ofa giant elephant…like creature known at first as “the great american incognitum” but lateridentified； not quite correctly； as a mammoth。 the first of these bones had been discovered ata place called big bone lick in kentucky； but soon others were turning up all over。 america；it appeared； had once been the home of a truly substantial creature—one that would surelydisprove buffon’s foolish gallic contentions。
in their keenness to demonstrate the incognitum’s bulk and ferocity； the americannaturalists appear to have bee slightly carried away。 they overestimated its size by afactor of six and gave it frightening claws； which in fact came from a megalonyx； or giantground sloth； found nearby。 rather remarkably； they persuaded themselves that the animalhad enjoyed “the agility and ferocity of the tiger；” and portrayed it in illustrations as pouncingwith feline grace onto prey from boulders。 when tusks were discovered； they were forced intothe animal’s head in any number of inventive ways。 one restorer screwed the tusks in upsidedown； like the fangs of a saber…toothed cat； which gave it a satisfyingly aggressive aspect。
another arranged the tusks so that they curved backwards on the engaging theory that thecreature had been aquatic and had used them to anchor itself to trees while dozing。 the mostpertinent consideration about the incognitum； however； was that it appeared to be extinct—afact that buffon cheerfully seized upon as proof of its incontestably degenerate nature。
buffon died in 1788； but the controversy rolled on。 in 1795 a selection of bones made theirway to paris； where they were examined by the rising star of paleontology； the youthful andaristocratic georges cuvier。 cuvier was already dazzling people with his genius for takingheaps of disarticulated bones and whipping them into shapely forms。 it was said that he coulddescribe the look and nature of an animal from a single tooth or scrap of jaw； and often namethe species and genus into the bargain。 realizing that no one in america had thought to writea formal description of the lumbering beast； cuvier did so； and thus became its officialdiscoverer。 he called it a mastodon （which means； a touch unexpectedly； “nipple…teeth”）。
inspired by the controversy； in 1796 cuvier wrote a landmark paper； note on the species ofliving and fossil elephants； in which he put forward for the first time a formal theory ofextinctions。 his belief was that from time to time the earth experienced global catastrophes inwhich groups of creatures were wiped out。 for religious people； including cuvier himself； theidea raised unfortable implications since it suggested an unaccountable casualness on thepart of providence。 to what end would god create species only to wipe them out later？ thenotion was contrary to the belief in the great chain of being； which held that the world wascarefully ordered and that every living thing within it had a place and purpose； and always hadand always would。 jefferson for one couldn’t abide the thought that whole species would everbe permitted to vanish （or； e to that； to evolve）。 so when it was put to him that theremight be scientific and political value in sending a party to explore the interior of americabeyond the mississippi he leapt at the idea； hoping the intrepid adventurers would find herdsof healthy mastodons and other outsized creatures grazing on the bounteous plains。
jefferson’s personal secretary and trusted friend meriwether lewis was chosen co…leader andchief naturalist for the expedition。 the person selected to advise him on what to look out forwith regard to animals living and deceased was none other than caspar wistar。
in the same year—in fact； the same month—that the aristocratic and celebrated cuvier waspropounding his extinction theories in paris； on the other side of the english channel a rathermore obscure englishman was having an insight into the value of fossils that would also havelasting ramifications。 william smith was a young supervisor of construction on the somersetcoal canal。 on the evening of january 5； 1796； he was sitting in a coaching inn in somersetwhen he jotted down the notion that would eventually make his reputation。 to interpret rocks；there needs to be some means of correlation； a basis on which you can tell that thosecarboniferous rocks from devon are younger than these cambrian rocks from wales。 smith’sinsight was to realize that the answer lay with fossils。 at every change in rock strata certainspecies of fossils disappeared while others carried on into subsequent levels。 by noting which species appeared in which strata； you could work out the relative ages of rocks wherever theyappeared。 drawing on his knowledge as a surveyor； smith began at once to make a map ofbritain’s rock strata； which would be published after many trials in 1815 and would bee acornerstone of modern geology。 （the story is prehensively covered in simonwinchester’s popular book the map that changed the world 。）unfortunately； having had his insight； smith was curiously uninterested in understandingwhy rocks were laid down in the way they were。 “i have left off puzzling about the origin ofstrata and content myself with knowing that it is so；” he recorded。 “the whys and whereforescannot e within the province of a mineral surveyor。”
smith’s revelation regarding strata heightened the moral awkwardness concerningextinctions。 to begin with； it confirmed that god had wiped out creatures not occasionally butrepeatedly。 this made him seem not so much careless as peculiarly hostile。 it also made itinconveniently necessary to explain how some species were wiped out while others continuedunimpeded into succeeding eons。 clearly there was more to extinctions than could beaccounted for by a single noachian deluge； as the biblical flood was known。 cuvier resolvedthe m