the.lost.world-第29章

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t　in　diameter；　constructed　of　one…inch　titanium　bars。　〃What　do　you　want　me　to　do　with　this？〃　Eddie　said。
　　　　〃Leave　it　down　there；〃　Levine　said。　〃That's　where　it　belongs。〃
　　　　Eddie　set　the　cage　upright　in　the　corner　of　the　scaffolding。　Levine　climbed　down。
　　　　〃And　what's　that　for？〃　Arby　said；　looking　down。　〃Catching　a　dinosaur？〃
　　　　In　point　of　fact；　just　the　opposite。〃　Levine　clipped　the　cage　to　the　side　of　the　scaffolding。　He　swung　the　door　open　and　shut；　testing　it。　There　was　a　lock　in　the　door。　He　checked　the　lock；　too；　leaving　the　key　in　place；　with　its　dangling　elastic　loop。　〃It's　a　predator　cage；　like　a　shark　〃　Levine　said；　〃If　you're　down　here　walking　around　and　anything　happens；　you　can　climb　in　here；　and　you'll　be　safe。〃
　　　　〃In　case　what　happens？〃　Arby　said；　with　a　worried　look。
　　　　〃Actually；　I　don't　think　anything　will　happen；〃　Levine　said。　〃Because　I　doubt　the　animals　will　pay　any　attention　to　us；　or　to　this　little　house；　once　the　structure's　been　concealed。〃
　　　　〃You　mean　they　won't　see　it？〃
　　　　〃Oh；　they'll　see　it；〃　Levine　said；　〃but　they'll　ignore　it。〃
　　　　〃But　if　they　smell　us。。。〃
　　　　Levine　shook　his　head。　〃We　sited　the　hide　so　the　prevailing　wind　is　toward　us。　And　you　may　have　noticed　these　ferns　have　a　distinct　smell。〃　It　was　a　mild；　slightly　tangy　odor；　almost　like　eucalyptus。
　　　　Arby　fretted。　〃But　suppose　they　decide　to　eat　the　ferns？〃
　　　　〃They　won't；〃　Levine　said。　〃These　are　Dicranopterus　cyatheoides。　They're　mildly　toxic　and　cause　a　rash　in　the　month。　In　point　of　fact；　there's　a　theory　that　their　toxicity　first　evolved　back　in　the　Jurassic；　as　a　defense　against　dinosaur　browsers。〃
　　　　〃That's　not　a　theory；〃　Malcolm　said。　〃It's　just　idle　speculation。〃
　　　　〃There's　some　logic　behind　it；〃　Levine　said。　〃Plant　life　in　the　Mesozoic　must　have　been　severely　challenged　by　the　arrival　of　very　large　dinosaurs。　Herds　of　giant　herbivores；　each　animal　consuming　hundreds　of　pounds　of　plant　matter　each　day；　would　have　wiped　out　any　plants　that　didn't　evolve　some　defense　…　a　bad　taste；　or　nettles；　or　thorns；　or　chemical　toxicity。　So　perhaps　cyatheoides　evolved　its　toxicity　back　then。　And　it's　very　effective；　because　contemporary　animals　don't　eat　these　ferns；　anywhere　on　earth。　That's　why　they're　so　abundant。　You　may　have　noticed。〃
　　　　〃Plants　have　defenses？〃　Kelly　said。
　　　　〃Of　course　they　do。　Plants　evolve　like　every　other　form　of　life；　and　they've　e　up　with　their　own　forms　of　aggression；　defense；　and　so　on。　In　the　nineteenth　century；　most　theories　concerned　animals　…　nature　red　in　tooth　and　claw；　all　that。　But　now　scientists　are　thinking　about　nature　green　in　root　and　stem。　We　realize　that　plants；　in　their　ceaseless　struggle　to　survive；　have　evolved　everything　from　plex　symbiosis　with　other　animals；　to　signaling　mechanisms　to　warn　other　plants；　to　outright　chemical　warfare。〃
　　　　Kelly　frowned。　〃Signaling？　Like　what？〃
　　　　〃Oh；　there　are　many　examples；〃　Levine　said。　〃In　Africa　acacia　trees　evolved　very　long；　sharp　thorns　…　three　inches　or　so　…　but　that　only　provoked　animals　like　giraffes　and　antelope　to　evolve　long　tongues　to　get　past　the　thorns。　Thorns　alone　didn't　work。　So　in　the　evolutionary　arms　race；　the　acacia　trees　next　evolved　toxicity。　They　started　to　produce　large　quantities　of　tannin　in　their　leaves；　which　sets　off　a　lethal　metabolic　reaction　in　the　animals　that　eat　them。　Literally　kills　them。　At　the　same　time；　the　acacias　also　evolved　a　kind　of　chemical　warning　system　among　themselves。　If　an　antelope　begins　to　eat　one　tree　in　a　grove；　that　tree　releases　the　chemical　ethylene　into　the　air；　which　causes　other　trees　in　the　grove　to　step　up　the　production　of　leaf　tannin。　Within　five　or　ten　minutes；　the　other　trees　are　producing　more　tannin；　making　themselves　poisonous。
　　　　〃And　then　what　happens　to　the　antelope？　It　dies？〃
　　　　〃Well；　not　any　more；〃　Levine　said；　〃because　the　evolutionary　arms　race　continued；　Eventually；　antelopes　learned　that　they　could　only　browse　for　a　short　time。　Once　the　trees　started　to　produce　more　tannin；　they　had　to　stop　eating　it。　And　the　browsers　developed　new　strategies。　For　example；　when　a　giraffe　eats　an　acacia　tree；　it　then　avoids　all　the　trees　downwind。　Instead；　it　moves　on　to　another　tree　that　is　some　distance　away。　So　the　animals　have　adapted　to　this　defense；　too。〃
　　　　〃In　evolutionary　theory；　this　is　called　the　Red　Queen　phenomenon；〃　Malcolm　said。　〃Because　in　Alice　in　Wonderland　the　Red　Queen　tells　Alice　she　has　to　run　as　fast　as　she　can　just　to　stay　where　she　is。　That's　the　way　evolutionary　spirals　seem。　All　the　organisms　are　evolving　at　a　furious　pace　just　to　stay　in　the　same　balance。　To　stay　where　they　are。〃
　　　　Arby　said；　〃And　this　is　mon？　Even　with　plants？〃
　　　　〃Oh　yes；〃　Levine　said。　〃In　their　own　way；　plants　are　extremely　active。　Oak　trees；　for　example；　produce　tannin　and　phenol　as　a　defense　when　caterpillars　attack　them。　A　whole　grove　of　trees　is　alerted　as　soon　as　one　tree　is　infested。　It's　a　way　to　protect　the　entire　grove　…　a　kind　of　cooperation　among　trees；　you　might　say。〃
　　　　Arby　nodded；　and　looked　out　from　the　high　hide　at　the　apatosaurs；　still　by　the　river　below。　〃So；〃　Arby　said；　〃is　that　why　the　dinosaurs　haven't　eaten　all　the　trees　off　this　island？　Because　those　big　apatosaurs　must　eat　a　lot　of　plants。　They　have　long　necks　to　eat　the　high　leaves。　But　the　trees　hardly　look　touched。〃
　　　　〃Very　good；〃　Levine　said；　nodding；　〃I　noticed　that　myself。〃
　　　　〃Is　that　because　of　these　plant　defenses？〃
　　　　〃Well；　it　might　be；〃　Levine　said。　〃But　I　think　there　is　a　very　simple　explanation　for　why　the　trees　are　preserved。〃
　　　　〃What's　that？〃
　　　　〃Just　look；〃　Levine　said。　〃It's　right　before　your　eyes。〃

Arby　picked　up　the　binoculars　and　stared　at　the　herds。　〃What's　the　simple　explanation？〃
　　　　〃Among　paleontologists；〃　Levine　said；　〃there's　been　an　interminable　debate　about　why　sauropods　have　long　necks。　Those　animals　you　see　have　necks　twenty　feet　long。　The　traditional　belief　has　been　that　sauropods　evolved　long　necks　to　eat　high　foliage　that　could　not　be；　reached　by　smaller　animals。〃
　　　　〃So？〃　Arby　said。　〃What's　the　debate？〃
　　　　〃Most　animals　on　this　planet　have　short　necks；〃　Levine　said；　〃because　a　long　neck　is；　well；　a　pain　in　the　neck。　It　causes　all　sorts　of　problems。　Structural　problems：　how　to　arrange　muscles　and　ligaments　to　support　a　long　neck。　Behavioral　problems：　nerve　impulses　must　travel　a　long　way　from　the　brain　to　the　body。　Swallowing　problems：　food　has　to　go　a　long　way　from　the　mouth　to　the　stomach。　Breathing　problems：　air　has　to　be　pulled　down　a　long　windpipe。　Cardiac　problems：　blood　has　to　be　pumped　way　up　to　the　head；　or　the　animal　faints；　In　evolutionary　terms；　all　this　is　very　difficult　to　do。〃
　　　　〃But　giraffes　do　it；〃　Arby　said。
　　　　〃Yes；　they　do。　Although　giraffe　necks　are　nowhere　near　this　long。　Giraffes　have　evolved　large　hearts；　and　very　thick　fascia　around　the　neck。　In　effect；　the　neck　of　a　giraffe　is　like　a　blood…pressure　cuff；　going　all　the　way　up。〃
　　　　〃Do　dinosaurs　have　the　same　cuff？〃
　　　　〃We　don't　know。　We　assume　apatosaurs　have　huge　hearts；　perhaps　three　hundred　pounds　or　more。　But　there　is　another　possible　solution　to　the　problem　of　pumping　blood　in　a　long　neck。〃
　　　　〃Yes？〃
　　　　〃You're　looking　at　it　right　now；〃　Levine　said。
　　　　Arby　clapped　his　hands。　〃They　don't　raise　their　necks！〃
　　　　〃Correct；〃　Levine　said。　〃At　least；　not　very　often；　or　for　long　periods。　Of　course；　right　now　the　animals　are　drinking；　so　their　necks　are　down；　but　my　guess　is　that　if　we　watch　them　for　an　extended　period　we'll　find　they　don't　spend　much　time　with　their　necks　raised　high。〃
　　　　〃And　that's　why　they　don't　eat　the　leaves　on　the　trees！〃
　　　　〃Right。〃
　　　　Kelly　frowned。　〃But　if　their　long　necks　aren't　used　for　eating；　then　why　did　they　evolve　them　in　the　first　place？〃
　　　　Levine　smiled。　〃There　must　be　a　good　reason；〃　he　said。　〃I　believe　it　has　to　do　with　defense。〃
　　　　〃Defense？　Long　necks？〃　Arby　stared。　〃I　don't　get　it。〃
　　　　〃Keep　looking；〃　Levine　said。　〃It's　really　rather　obvious。〃
　　　　Arbv　peered　through　binoculars。　He　said　to　Kelly；　〃I　hate　it　when　he　tells　us　it's　obvious。〃
　　　　〃I　know；〃　she　said；　with　a　sigh。
　　　　Arby　glanced　over　at　Thorne；　and　caught　his　eye。　Thorne　made　a　V　with　his　fingers；　and　then　pushed　one　finger；　tilting　it　over。　The　movement　forced　the　second　finger　to　shift；　too。　So　the　two　fingers　were　connected。。。。
　　　　If　it　was　a　clue；　he　didn't　get　it。　He　didn't　get　it。　He　frowned。
　　　　Thorne　mouthed：　〃Bridge。〃
　　　　Arby　looked；　and　watched　the　whip…like　tails　swing　back　and　forth　over　the　younger　animals。　〃I　get　it！〃　Arby　said。　〃They　use　their　tails　for　defense。　And　they　need　long　necks　to　counterbalance　the　long　tails。　It's　like　a　suspension　bridge！〃
　　　　Levine　squinted　at　Arby。　〃You　did　that　very　fast；〃　he　said。
　　　　Thorne　turned　away；　hiding　a　smile。
　　　　〃But　I'm　right。。。〃　Arby　said。
　　　　〃Yes；〃　Levine　said；　〃your　view　is　essentially　correct。　Long　necks　exist　because　the　long　tails　exist。　It's　a　different　Situation　in　theropods；　which　stand　on　two　legs。　But　in　quadrupeds；　there　needs　to　be　a　counterbalance　for　the　long　tail；　or　the　animal　would　simply　tip　over。〃
　　　　Malcolm　said；　〃Actually；　there　is　something　much　more　puzzling　about　this　apatosaur　herd。〃
　　　　Oh？〃　Levine　said。　〃What's　that？〃
　　　　〃There　are　no　true　adults；〃　Malcolm　said。　〃Those　animals　we　see　are　very　large　by　our　standards。　But　in　fact；　none　of　them　has　attained　full　adult　size。　I　find　that　perplexing。〃
　　　　〃Do　you？　It　doesn't　trouble　me　in　the　least；〃　Levine　said。　〃Unquestionably；　it　is　simply　because　they　haven't　had　enough　time　to　reach　maturity。　I'm　sure　apatosaurs　grow　more　slowly　than　the　other　dinosaurs。　After　all；　large　mammals　like　elephants　grow　more　slowly　than　small　ones。
　　　　Malcolm　shook　his　head。　〃That's　not　the　explanation；〃　he　said。
　　　　〃Oh？　Then　what？〃
　　　　〃Keep　looking；〃　Malcolm　said；　pointing　out　over　the　plain。　〃It's　really　rather　obvious。〃
　　　　The　kids　giggled。
　　　　Levine　gave　a　little　shiver　of　displeasure。　〃What　is　obvious　to　me；〃　he　said；　〃is　that　none　of　the　species　appear　to　have　attained　full　adulthood。　The　triceratops；　the　apatosaurs；　even　the　parasaurs　are　a　bit　smaller　than　one　would　expect。　This　argues　for　a　consistent　factor：　some　element　of　diet；　the　effects　of　confinement　on　a　small　island；　perhaps　even　the　way　they　were　engineered。　But　I　don't　consider　it　particularly　remarkable　or　worrisome。〃
　　　　〃Maybe　you're　right；〃　Malcolm　said。　〃And　then　again；　maybe　you're　not。〃

Puerto　Cortés
　　　　
〃No　flights？〃　Sarah　Harding　said。　〃What　do　you　mean；　there　are　no　flights？〃　It　was　eleven　o'clock　in　the　morning。　Harding　had　been　flying　for　the　last　fifteen　hours；　much　of　it　spent　on　a　U。S。　military　transport　that　she'd　caught　from　Nairobi　to　Dallas。　She　was　exhausted。　Her　skin　felt　grimy；　she　needed　a　shower　and　a　change　of　clothes。　Instead　she　found　herself　arguing　with　this　very　stubborn　official　in　a　ratty　little　town　on　the　west　coast　of　Costa　Rica。　Outside；　the　fain　had　stopped；　but　the　sky　was　still　gray；　with　low…hanging　clouds　over　the　deserted　airfield。
　　　　〃I　am　sorry；〃　Rodríguez　said。　〃No　flights　can　be　arranged。〃
　　　　〃But　what　about　the　helicopter　that　took　the　men　earlier？〃
　　　　〃There　is　a　helicopter；　yes。〃
　　　　〃Where　is　it？〃
　　　　〃The　helicopter　is　not　here。〃
　　　　〃I　can　see　that。