万物简史英文版_比尔·布莱森-第70章

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arter　of　all　prescribed　medicines　are　derived　from　just　forty　plants；　withanother　16　percent　ing　from　animals　or　microbes；　so　there　is　a　serious　risk　with　everyhectare　of　forest　felled　of　losing　medically　vital　possibilities。　using　a　method　calledbinatorial　chemistry；　chemists　can　generate　forty　thousand　pounds　at　a　time　in　labs；but　these　products　are　random　and　not　unmonly　useless；　whereas　any　natural　moleculewill　have　already　passed　what　the　economist　calls　鈥渢he　ultimate　screening　programme：　overthree　and　a　half　billion　years　of　evolution。鈥�

looking　for　the　unknown　isn鈥檛　simply　a　matter　of　traveling　to　remote　or　distant　places；however。　in　his　book　life：　an　unauthorised　biography；　richard　fortey　notes　how　oneancient　bacterium　was　found　on　the　wall　of　a　country　pub　鈥渨here　men　had　urinated　forgenerations鈥濃�攁　discovery　that　would　seem　to　involve　rare　amounts　of　luckand　devotion　andpossibly　some　other　quality　not　specified。

there　aren鈥檛　enough　specialists。the　stock　of　things　to　be　found；　examined；　and　recordedvery　much　outruns　the　supply　of　scientists　available　to　do　it。　take　the　hardy　and　little…knownorganisms　known　as　bdelloid　rotifers。　these　are　microscopic　animals　that　can　survive　almostanything。　when　conditions　are　tough；　they　curl　up　into　a　pact　shape；　switch　off　theirmetabolism；　and　wait　for　better　times。　in　this　state；　you　can　drop　them　into　boiling　water　orfreeze　them　almost　to　absolute　zero鈥攖hat　is　the　level　where　even　atoms　give　up鈥攁nd；　whenthis　torment　has　finished　and　they　are　returned　to　a　more　pleasing　environment；　they　willuncurl　and　move　on　as　if　nothing　has　happened。　so　far；　about　500　species　have　been　identified（though　other　sources　say　360）；　but　nobody　has　any　idea；　even　remotely；　how　many　there　maybe　altogether。　for　years　almost　all　that　was　known　about　them　was　thanks　to　the　work　of　adevoted　amateur；　a　london　clerical　worker　named　david　bryce　who　studied　them　in　his　sparetime。　they　can　be　found　all　over　the　world；　but　you　could　have　all　the　bdelloid　rotifer　expertsin　the　world　to　dinner　and　not　have　to　borrow　plates　from　the　neighbors。

even　something　as　important　and　ubiquitous　as　fungi鈥攁nd　fungi　are　both鈥攁ttractsparatively　little　notice。　fungi　are　everywhere　and　e　in　many　forms鈥攁s　mushrooms；molds；　mildews；　yeasts；　and　puffballs；　to　name　but　a　sampling鈥攁nd　they　exist　in　volumesthat　most　of　us　little　suspect。　gather　together　all　the　fungi　found　in　a　typical　acre　of　meadowand　you　would　have　2；500　pounds　of　the　stuff。　these　are　not　marginal　organisms。　withoutfungi　there　would　be　no　potato　blights；　dutch　elm　disease；　jock　itch；　or　athlete鈥檚　foot；　but　alsono　yogurts　or　beers　or　cheeses。　altogether　about　70；000　species　of　fungi　have　been　identified；but　it　is　thought　the　number　could　be　as　high　as　1。8　million。　a　lot　of　mycologists　work　inindustry；　making　cheeses　and　yogurts　and　the　like；　so　it　is　hard　to　say　how　many　are　activelyinvolved　in　research；　but　we　can　safely　take　it　that　there　are　more　species　of　fungi　to　be　foundthan　there　are　people　to　find　them。

the　world　is　a　really　big　place。we　have　been　gulled　by　the　ease　of　air　travel　and　otherforms　of　munication　into　thinking　that　the　world　is　not　all　that　big；　but　at　ground　level；where　researchers　must　work；　it　is　actually　enormous鈥攅normous　enough　to　be　full　ofsurprises。　the　okapi；　the　nearest　living　relative　of　the　giraffe；　is　now　known　to　exist　insubstantial　numbers　in　the　rain　forests　of　zaire鈥攖he　total　population　is　estimated　at　perhapsthirty　thousand鈥攜et　its　existence　wasn鈥檛　even　suspected　until　the　twentieth　century。　the　largeflightless　new　zealand　bird　called　the　takahe　had　been　presumed　extinct　for　two　hundredyears　before　being　found　living　in　a　rugged　area　of　the　country鈥檚　south　island。　in　1995　a　teamof　french　and　british　scientists　in　tibet；　who　were　lost　in　a　snowstorm　in　a　remote　valley；came　across　a　breed　of　horse；　called　the　riwoche；　that　had　previously　been　known　only　fromprehistoric　cave　drawings。　the　valley鈥檚　inhabitants　were　astonished　to　learn　that　the　horse　wasconsidered　a　rarity　in　the　wider　world。

some　　people　　think　　even　　greater　　surprises　may　await　us。　鈥渁　leading　british　ethno…biologist；鈥潯�wrote　the　economist　in　1995；　鈥渢hinks　a　megatherium；　a　sort　of　giant　ground　slothwhich　may　stand　as　high　as　a　giraffe　。　。　。　may　lurk　in　the　fastnesses　of　the　amazon　basin。鈥�

perhaps　significantly；　the　ethnobiologist　wasn鈥檛　named；　perhaps　even　more　significantly；nothing　more　has　been　heard　of　him　or　his　giant　sloth。　no　one；　however；　can　categorically　saythat　no　such　thing　is　there　until　every　jungly　glade　has　been　investigated；　and　we　are　a　longway　from　achieving　that。

but　even　if　we　groomed　thousands　of　fieldworkers　and　dispatched　them　to　the　farthestcorners　of　the　world；　it　would　not　be　effort　enough；　for　wherever　life　can　be；　it　is。　life鈥檚extraordinary　fecundity　is　amazing；　even　gratifying；　but　also　problematic。　to　survey　it　all；　youwould　have　to　turn　over　every　rock；　sift　through　the　litter　on　every　forest　floor；　sieveunimaginable　quantities　of　sand　and　dirt；　climb　into　every　forest　canopy；　and　devise　muchmore　efficient　ways　to　examine　the　seas。　even　then　you　would　overlook　whole　ecosystems。　inthe　1980s；　spelunkers　entered　a　deep　cave　in　romania　that　had　been　sealed　off　from　theoutside　world　for　a　long　but　unknown　period　and　found　thirty…three　species　of　insects　andother　small　creatures鈥攕piders；　centipedes；　lice鈥攁ll　blind；　colorless；　and　new　to　science。

they　were　living　off　the　microbes　in　the　surface　scum　of　pools；　which　in　turn　were　feeding　onhydrogen　sulfide　from　hot　springs。

our　instinct　may　be　to　see　the　impossibility　of　tracking　everything　down　as　frustrating；dispiriting；　perhaps　even　appalling；　but　it　can　just　as　well　be　viewed　as　almost　unbearablyexciting。　we　live　on　a　planet　that　has　a　more　or　less　infinite　capacity　to　surprise。　whatreasoning　person　could　possibly　want　it　any　other　way？

what　is　nearly　always　most　arresting　in　any　ramble　through　the　scattered　disciplines　ofmodern　science　is　realizing　how　many　people　have　been　willing　to　devote　lifetimes　to　themost　sumptuously　esoteric　lines　of　inquiry。　in　one　of　his　essays；　stephen　jay　gould　notes　howa　hero　of　his　named　henry　edward　crampton　spent　fifty　years；　from　1906　to　his　death　in1956；　quietly　studying　a　genus　of　land　snails　in　polynesia　called　partula。　over　and　over；　yearafter　year；　crampton　measured　to　the　tiniest　degree鈥攖o　eight　decimal　places鈥攖he　whorls　andarcs　and　gentle　curves　of　numberless　partula；　piling　the　results　into　fastidiously　detailedtables。　a　single　line　of　text　in　a　crampton　table　could　represent　weeks　of　measurement　andcalculation。

only　slightly　less　devoted；　and　certainly　more　unexpected；　was　alfred　c。　kinsey；　whobecame　famous　for　his　studies　of　human　sexuality　in　the　1940s　and　1950s。　but　before　hismind　became　filled　with　sex；　so　to　speak；　kinsey　was　an　entomologist；　and　a　dogged　one　atthat。　in　one　expedition　lasting　two　years；　he　hiked　2；500　miles　to　assemble　a　collection　of300；000　wasps。　how　many　stings　he　collected　along　the　way　is　not；　alas；　recorded。

something　that　had　been　puzzling　me　was　the　question　of　how　you　assured　a　chain　ofsuccession　in　these　arcane　fields。　clearly　there　cannot　be　many　institutions　in　the　world　thatrequire　or　are　prepared　to　support　specialists　in　barnacles　or　pacific　snails。　as　we　parted　at　thenatural　history　museum　in　london；　i　asked　richard　fortey　how　science　ensures　that　whenone　person　goes　there鈥檚　someone　ready　to　take　his　place。

he　chuckled　rather　heartily　at　my　naivet茅。　鈥渋鈥檓　afraid　it鈥檚　not　as　if　we　have　substitutessitting　on　the　bench　somewhere　waiting　to　be　called　in　to　play。　when　a　specialist　retires　or；even　more　unfortunately；　dies；　that　can　bring　a　stop　to　things　in　that　field；　sometimes　for　avery　long　while。鈥�

鈥渁nd　i　suppose　that鈥檚　why　you　value　someone　who　spends　forty…two　years　studying　asingle　species　of　plant；　even　if　it　doesn鈥檛　produce　anything　terribly　new？鈥�

鈥減recisely；鈥潯�he　said；　鈥減recisely。鈥潯�and　he　really　seemed　to　mean　it。





24　　　　CELLS

灏彙�璇础璽…xt…澶�。鍫�
it　starts　with　a　single　cell。　the　first　cell　splits　to　bee　two　and　the　two　bee　fourand　so　on。　after　just　forty…seven　doublings；　you　have　ten　thousand　trillion（10；000；000；000；000；000）　cells　in　your　body　and　are　ready　to　spring　forth　as　a　human　being。

1and　every　one　of　those　cells　knows　exactly　what　to　do　to　preserve　and　nurture　you　from　themoment　of　conception　to　your　last　breath。

you　have　no　secrets　from　your　cells。　they　know　far　more　about　you　than　you　do。　each　onecarries　a　copy　of　the　plete　genetic　code鈥攖he　instruction　manual　for　your　body鈥攕o　itknows　not　only　how　to　do　its　job　but　every　other　job　in　the　body。　never　in　your　life　will　youhave　to　remind　a　cell　to　keep　an　eye　on　its　adenosine　triphosphate　levels　or　to　find　a　place　forthe　extra　squirt　of　folic　acid　that鈥檚　just　unexpectedly　turned　up。　it　will　do　that　for　you；　andmillions　more　things　besides。

every　cell　in　nature　is　a　thing　of　wonder。　even　the　simplest　are　far　beyond　the　limits　ofhuman　ingenuity。　to　build　the　most　basic　yeast　cell；　for　example；　you　would　have　tominiaturize　about　the　same　number　of　ponents　as　are　found　in　a　boeing　777　jetliner　andfit　them　into　a　sphere　just　five　microns　across；　then　somehow　you　would　have　to　persuade　thatsphere　to　reproduce。

but　yeast　cells　are　as　nothing　pared　with　human　cells；　which　are　not　just　more　variedand　plicated；　but　vastly　more　fascinating　because　of　their　plex　interactions。

your　cells　are　a　country　of　ten　thousand　trillion　citizens；　each　devoted　in　some　intensivelyspecific　way　to　your　overall　well…being。　there　isn鈥檛　a　thing　they　don鈥檛　do　for　you。　they　letyou　feel　pleasure　and　form　thoughts。　they　enable　you　to　stand　and　stretch　and　caper。　whenyou　eat；　they　extract　the　nutrients；　distribute　the　energy；　and　carry　off　the　wastes鈥攁ll　thosethings　you　learned　about　in　junior　high　school　biology鈥攂ut　they　also　remember　to　make　youhungry　in　the　first　place　and　reward　you　with　a　feeling　of　well…being　afterward　so　that　youwon鈥檛　forget　to　eat　again。　they　keep　your　hair　growing；　your　ears　waxed；　your　brain　quietlypurring。　they　manage　every　corner　of　your　being。　they　will　jump　to　your　defense　the　instantyou　are　threatened。　they　will　unhesitatingly　die　for　you鈥攂illions　of　them　do　so　daily。　andnot　once　in　all　your　years　have　you　thanked　even　one　of　them。　so　let　us　take　a　moment　now　toregard　them　with　the　wonder　and　appreciation　they　deserve。

we　understand　a　little　of　how　cells　do　the　things　they　do鈥攈ow　they　lay　down　fat　ormanufacture　insulin　or　engage　in　many　of　the　other　acts　necessary　to　maintain　a　plicatedentity　like　yourself鈥攂ut　only　a　little。　you　have　at　least　200；000　different　types　of　protein1actually；　quite　a　lot　of　cells　are　lost　in　the　process　of　development；　so　the　number　you　emerge　with　is　reallyjust　a　guess。　depending　on　which　source　you　consult　the　number　can　vary　by　several　orders　of　magnitude。　thefigure　of　ten　thousand　trillion　（or　quadrillion）　is　from　margulis　and　sagan；　1986。

laboring　away　inside　you；　and　so　far　we　understand　what　no　more　than　about　2　percent　ofthem　do。　（others　put　the　figure　at　more　like　50　percent；　it　depends；　apparently；　on　what　youmean　by　鈥渦nderstand。鈥潱﹕urprises　at　the　ce