万物简史英文版_比尔·布莱森-第84章

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in　our　years　of　collaboration　at　the　institute　he　＇johanson＇　developed　a　well…deserved；　if　unfortunate；　reputation　for　unpredictable　and　high…decibel　personalverbal　assaults；　sometimes　acpanied　by　the　tossing　around　of　books　orwhatever　else　came　conveniently　to　hand。

so；　bearing　in　mind　that　there　is　little　you　can　say　about　human　prehistory　that　won鈥檛　bedisputed　by　someone　somewhere；　other　than　that　we　most　certainly　had　one；　what　we　thinkwe　know　about　who　we　are　and　where　we　e　from　is　roughly　this：

for　the　first　99。99999　percent　of　our　history　as　organisms；　we　were　in　the　same　ancestralline　as　chimpanzees。　virtually　nothing　is　known　about　the　prehistory　of　chimpanzees；　butwhatever　they　were；　we　were。　then　about　seven　million　years　ago　something　major　happened。

a　group　of　new　beings　emerged　from　the　tropical　forests　of　africa　and　began　to　move　abouton　the　open　savanna。

these　were　the　australopithecines；　and　for　the　next　five　million　years　they　would　be　theworld鈥檚　dominant　hominid　species。　（austral　is　from　the　latin　for　鈥渟outhern鈥潯�and　has　noconnection　in　this　context　to　australia。）　australopithecines　came　in　several　varieties；　someslender　and　gracile；　like　raymond　dart鈥檚　taung　child；　others　more　sturdy　and　robust；　but　allwere　capable　of　walking　upright。　some　of　these　species　existed　for　well　over　a　million　years；others　for　a　more　modest　few　hundred　thousand；　but　it　is　worth　bearing　in　mind　that　even　theleast　successful　had　histories　many　times　longer　than　we　have　yet　achieved。

the　most　famous　hominid　remains　in　the　world　are　those　of　a　3。18…million…year…oldaustralopithecine　found　at　hadar　in　ethiopia　in　1974　by　a　team　led　by　donald　johanson。

formally　known　as　a。l。　（for　鈥渁far　locality鈥潱�　288鈥�1；　the　skeleton　became　more　familiarlyknown　as　lucy；　after　the　beatles　song　鈥渓ucy　in　the　sky　with　diamonds。鈥潯�johanson　has　neverdoubted　her　importance。　鈥渟he　is　our　earliest　ancestor；　the　missing　link　between　ape　andhuman；鈥潯�he　has　said。

lucy　was　tiny鈥攋ust　three　and　a　half　feet　tall。　she　could　walk；　though　how　well　is　a　matterof　some　dispute。　she　was　evidently　a　good　climber；　too。　much　else　is　unknown。　her　skull　wasalmost　entirely　missing；　so　little　could　be　said　with　confidence　about　her　brain　size；　thoughskull　fragments　suggested　it　was　small。　most　books　describe　lucy鈥檚　skeleton　as　being　40percent　plete；　though　some　put　it　closer　to　half；　and　one　produced　by　the　americanmuseum　of　natural　history　describes　lucy　as　two…thirds　plete。　the　bbc　television　seriesape　man　actually　called　it　鈥渁　plete　skeleton；鈥潯�even　while　showing　that　it　was　anythingbut。

a　human　body　has　206　bones；　but　many　of　these　are　repeated。　if　you　have　the　left　femurfrom　a　specimen；　you　don鈥檛　need　the　right　to　know　its　dimensions。　strip　out　all　the　redundantbones；　and　the　total　you　are　left　with　is　120鈥攚hat　is　called　a　half　skeleton。　even　by　this　fairlyacmodating　standard；　and　even　counting　the　slightest　fragment　as　a　full　bone；　lucyconstituted　only　28　percent　of　a　half　skeleton　（and　only　about　20　percent　of　a　full　one）。

in　the　wisdom　of　the　bones；　alan　walker　recounts　how　he　once　asked　johanson　how　hehad　e　up　with　a　figure　of　40　percent。　johanson　breezily　replied　that　he　had　discounted　the106　bones　of　the　hands　and　feet鈥攎ore　than　half　the　body鈥檚　total；　and　a　fairly　important　half；too；　one　would　have　thought；　since　lucy鈥檚　principal　defining　attribute　was　the　use　of　thosehands　and　feet　to　deal　with　a　changing　world。　at　all　events；　rather　less　is　known　about　lucythan　is　generally　supposed。　it　isn鈥檛　even　actually　known　that　she　was　a　female。　her　sex　ismerely　presumed　from　her　diminutive　size。

two　years　after　lucy鈥檚　discovery；　at　laetoli　in　tanzania　mary　leakey　found　footprints　leftby　two　individuals　from鈥攊t　is　thought鈥攖he　same　family　of　hominids。　the　prints　had　beenmade　when　two　australopithecines　had　walked　through　muddy　ash　following　a　volcaniceruption。　the　ash　had　later　hardened；　preserving　the　impressions　of　their　feet　for　a　distance　ofover　twenty…three　meters。

the　american　museum　of　natural　history　in　new　york　has　an　absorbing　diorama　thatrecords　the　moment　of　their　passing。　it　depicts　life…sized　re…creations　of　a　male　and　a　femalewalking　side　by　side　across　the　ancient　african　plain。　they　are　hairy　and　chimplike　indimensions；　but　have　a　bearing　and　gait　that　suggest　humanness。　the　most　striking　feature　ofthe　display　is　that　the　male　holds　his　left　arm　protectively　around　the　female鈥檚　shoulder。　it　is　atender　and　affecting　gesture；　suggestive　of　close　bonding。

the　tableau　is　done　with　such　conviction　that　it　is　easy　to　overlook　the　consideration　thatvirtually　everything　above　the　footprints　is　imaginary。　almost　every　external　aspect　of　thetwo　figures鈥攄egree　of　hairiness；　facial　appendages　（whether　they　had　human　noses　or　chimpnoses）；　expressions；　skin　color；　size　and　shape　of　the　female鈥檚　breasts鈥攊s　necessarilysuppositional。　we　can鈥檛　even　say　that　they　were　a　couple。　the　female　figure　may　in　fact　havebeen　a　child。　nor　can　we　be　certain　that　they　were　australopithecines。　they　are　assumed　to　beaustralopithecines　because　there　are　no　other　known　candidates。

i　had　been　told　that　they　were　posed　like　that　because　during　the　building　of　the　dioramathe　female　figure　kept　toppling　over；　but　ian　tattersall　insists　with　a　laugh　that　the　story　isuntrue。　鈥渙bviously　we　don鈥檛　know　whether　the　male　had　his　arm　around　the　female　or　not；but　we　do　know　from　the　stride　measurements　that　they　were　walking　side　by　side　and　closetogether鈥攃lose　enough　to　be　touching。　it　was　quite　an　exposed　area；　so　they　were　probablyfeeling　vulnerable。　that鈥檚　why　we　tried　to　give　them　slightly　worried　expressions。鈥�

i　asked　him　if　he　was　troubled　about　the　amount　of　license　that　was　taken　in　reconstructingthe　figures。　鈥渋t鈥檚　always　a　problem　in　making　re…creations；鈥潯�he　agreed　readily　enough。　鈥測ouwouldn鈥檛　believe　how　much　discussion　can　go　into　deciding　details　like　whether　neandertalshad　eyebrows　or　not。　it　was　just　the　same　for　the　laetoli　figures。　we　simply　can鈥檛　know　thedetails　of　what　they　looked　like；　but　we　can　convey　their　size　and　posture　and　make　somereasonable　assumptions　about　their　probable　appearance。　if　i　had　it　to　do　again；　i　think　i　mighthave　made　them　just　slightly　more　apelike　and　less　human。　these　creatures　weren鈥檛　humans。

they　were　bipedal　apes。鈥�

until　very　recently　it　was　assumed　that　we　were　descended　from　lucy　and　the　laetolicreatures；　but　now　many　authorities　aren鈥檛　so　sure。　although　certain　physical　features　（theteeth；　for　instance）　suggest　a　possible　link　between　us；　other　parts　of　the　australopithecineanatomy　are　more　troubling。　in　their　book　extinct　humans；　tattersall　and　schwartz　point　outthat　the　upper　portion　of　the　human　femur　is　very　like　that　of　the　apes　but　not　of　theaustralopithecines；　so　if　lucy　is　in　a　direct　line　between　apes　and　modern　humans；　it　meanswe　must　have　adopted　an　australopithecine　femur　for　a　million　years　or　so；　then　gone　back　toan　ape　femur　when　we　moved　on　to　the　next　phase　of　our　development。　they　believe；　in　fact；that　not　only　was　lucy　not　our　ancestor；　she　wasn鈥檛　even　much　of　a　walker。

鈥渓ucy　and　her　kind　did　not　loote　in　anything　like　the　modern　human　fashion；鈥潯�insiststattersall。　鈥渙nly　when　these　hominids　had　to　travel　between　arboreal　habitats　would　they　findthemselves　walking　bipedally；　鈥榝orced鈥櫋�to　do　so　by　their　own　anatomies。鈥潯�johanson　doesn鈥檛accept　this。　鈥渓ucy鈥檚　hips　and　the　muscular　arrangement　of　her　pelvis；鈥潯�he　has　written；　鈥渨ouldhave　made　it　as　hard　for　her　to　climb　trees　as　it　is　for　modern　humans。鈥�

matters　grew　murkier　still　in　2001　and　2002　when　four　exceptional　new　specimens　werefound。　one；　discovered　by　meave　leakey　of　the　famous　fossil…hunting　family　at　laketurkana　in　kenya　and　called　kenyanthropus　platyops　（鈥渒enyan　flat…face鈥潱�；　is　from　about　thesame　time　as　lucy　and　raises　the　possibility　that　it　was　our　ancestor　and　lucy　was　anunsuccessful　side　branch。　also　found　in　2001　were　ardipithecus　ramidus　kadabba；　dated　atbetween　5。2　million　and　5。8　million　years　old；　and　orrorin　tugenensis；　thought　to　be　6　millionyears　old；　making　it　the　oldest　hominid　yet　found鈥攂ut　only　for　a　brief　while。　in　the　summerof　2002　a　french　team　working　in　the　djurab　desert　of　chad　（an　area　that　had　never　beforeyielded　ancient　bones）　found　a　hominid　almost　7　million　years　old；　which　they　labeledsahelanthropus　tchadensis。　（some　critics　believe　that　it　was　not　human；　but　an　early　ape　andtherefore　should　be　called　sahelpithecus。）　all　these　were　early　creatures　and　quite　primitivebut　they　walked　upright；　and　they　were　doing　so　far　earlier　than　previously　thought。

bipedalism　is　a　demanding　and　risky　strategy。　it　means　refashioning　the　pelvis　into　a　fullload…bearing　instrument。　to　preserve　the　required　strength；　the　birth　canal　must　beparatively　narrow。　this　has　two　very　significant　immediate　consequences　and　one　longer…term　one。　first；　it　means　a　lot　of　pain　for　any　birthing　mother　and　a　greatly　increased　dangerof　fatality　to　mother　and　baby　both。　moreover　to　get　the　baby鈥檚　head　through　such　a　tightspace　it　must　be　born　while　its　brain　is　still　small鈥攁nd　while　the　baby；　therefore；　is　stillhelpless。　this　means　long…term　infant　care；　which　in　turn　implies　solid　male鈥揻emale　bonding。

all　this　is　problematic　enough　when　you　are　the　intellectual　master　of　the　planet；　but　whenyou　are　a　small；　vulnerable　australopithecine；　with　a　brain　about　the　size　of　an　orange；3therisk　must　have　been　enormous。

3absolute　brain　size　does　not　tell　you　everything…or　possibly　sometimes　even　much。　elephants　and　whales　bothhave　brains　larger　than　ours；　but　you　wouldnt　have　much　trouble　outwitting　them　in　contract　negotiations。　it　isrelative　size　that　matters；　a　point　that　is　often　overlooked。　as　gould　notes；　a。　africanus　had　a　brain　of　only　450cubic　centimeters；　smaller　than　that　of　a　gorilla。　but　a　typical　africanus　male　weighed　less　than　a　hundredpounds；　and　a　female　much　less　still；　whereas　gorillas　can　easily　top　out　at　600　pounds　（gould　pp。　181…83）。

so　why　did　lucy　and　her　kind　e　down　from　the　trees　and　out　of　the　forests？　probablythey　had　no　choice。　the　slow　rise　of　the　isthmus　of　panama　had　cut　the　flow　of　waters　fromthe　pacific　into　the　atlantic；　diverting　warming　currents　away　from　the　arctic　and　leading　tothe　onset　of　an　exceedingly　sharp　ice　age　in　northern　latitudes。　in　africa；　this　would　haveproduced　seasonal　drying　and　cooling；　gradually　turning　jungle　into　savanna。　鈥渋t　was　not　somuch　that　lucy　and　her　like　left　the　forests；鈥潯�john　gribbin　has　written；　鈥渂ut　that　the　forestsleft　them。鈥�

but　stepping　out　onto　the　open　savanna　also　clearly　left　the　early　hominids　much　moreexposed。　an　upright　hominid　could　see　better；　but　could　also　be　seen　better。　even　now　as　aspecies；　we　are　almost　preposterously　vulnerable　in　the　wild。　nearly　every　large　animal　youcan　care　to　name　is　stronger；　faster；　and　toothier　than　us。　faced　with　attack；　modern　humanshave　only　two　advantages。　we　have　a　good　brain；　with　which　we　can　devise　strategies；　andwe　have　hands　with　which　we　can　fling　or　brandish　hurtful　objects。　we　are　the　only　creaturethat　can　harm　at　a　distance。　we　can　thus　afford　to　be　physically　vulnerable。

all　the　elements　would