按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
it was a little； i gathered； like following a road randomly out of london and finding thateventually it ends at john o鈥檊roats； and concluding from this that anyone in london musttherefore have e from the north of scotland。 they might have e from there； of course；but equally they could have arrived from any of hundreds of other places。 in this sense；according to harding； every gene is a different highway； and we have only barely begun tomap the routes。 鈥渘o single gene is ever going to tell you the whole story；鈥潯he said。
so genetic studies aren鈥檛 to be trusted？
鈥渙h you can trust the studies well enough； generally speaking。 what you can鈥檛 trust are thesweeping conclusions that people often attach to them。鈥�
she thinks out…of…africa is 鈥減robably 95 percent correct；鈥潯ut adds： 鈥渋 think both sides havedone a bit of a disservice to science by insisting that it must be one thing or the other。 thingsare likely to turn out to be not so straightforward as either camp would have you believe。 theevidence is clearly starting to suggest that there were multiple migrations and dispersals indifferent parts of the world going in all kinds of directions and generally mixing up the genepool。 that鈥檚 never going to be easy to sort out。鈥�
just at this time； there were also a number of reports questioning the reliability of claimsconcerning the recovery of very ancient dna。 an academic writing in nature had noted howa paleontologist； asked by a colleague whether he thought an old skull was varnished or not；had licked its top and announced that it was。 鈥渋n the process；鈥潯oted the nature article； 鈥渓argeamounts of modern human dna would have been transferred to the skull；鈥潯endering ituseless for future study。 i asked harding about this。 鈥渙h； it would almost certainly have beencontaminated already；鈥潯he said。 鈥渏ust handling a bone will contaminate it。 breathing on itwill contaminate it。 most of the water in our labs will contaminate it。 we are all swimming inforeign dna。 in order to get a reliably clean specimen you have to excavate it in sterileconditions and do the tests on it at the site。 it is the trickiest thing in the world not tocontaminate a specimen。鈥�
so should such claims be treated dubiously？ i asked。
harding nodded solemnly。 鈥渧ery；鈥潯he said。
if you wish to understand at once why we know as little as we do about human origins； ihave the place for you。 it is to be found a little beyond the edge of the blue ngong hills inkenya； to the south and west of nairobi。 drive out of the city on the main highway touganda； and there es a moment of startling glory when the ground falls away and you arepresented with a hang glider鈥檚 view of boundless； pale green african plain。
this is the great rift valley； which arcs across three thousand miles of east africa；marking the tectonic rupture that is setting africa adrift from asia。 here； perhaps forty milesout of nairobi； along the baking valley floor； is an ancient site called olorgesailie； which oncestood beside a large and pleasant lake。 in 1919； long after the lake had vanished； a geologistnamed j。 w。 gregory was scouting the area for mineral prospects when he came across astretch of open ground littered with anomalous dark stones that had clearly been shaped byhuman hand。 he had found one of the great sites of acheulean tool manufacture that iantattersall had told me about。
unexpectedly in the autumn of 2002 i found myself a visitor to this extraordinary site。 iwas in kenya for another purpose altogether； visiting some projects run by the charity careinternational； but my hosts； knowing of my interest in humans for the present volume； hadinserted a visit to olorgesailie into the schedule。
after its discovery by gregory； olorgesailie lay undisturbed for over two decades beforethe famed husband…and…wife team of louis and mary leakey began an excavation that isn鈥檛pleted yet。 what the leakeys found was a site stretching to ten acres or so； where toolswere made in incalculable numbers for roughly a million years； from about 1。2 million yearsago to 200；000 years ago。 today the tool beds are sheltered from the worst of the elementsbeneath large tin lean…tos and fenced off with chicken wire to discourage opportunisticscavenging by visitors； but otherwise the tools are left just where their creators dropped themand where the leakeys found them。
jillani ngalli； a keen young man from the kenyan national museum who had beendispatched to act as guide； told me that the quartz and obsidian rocks from which the axeswere made were never found on the valley floor。 鈥渢hey had to carry the stones from there；鈥潯esaid； nodding at a pair of mountains in the hazy middle distance； in opposite directions fromthe site： olorgesailie and ol esakut。 each was about ten kilometers； or six miles； away鈥攁long way to carry an armload of stone。
why the early olorgesailie people went to such trouble we can only guess； of course。 notonly did they lug hefty stones considerable distances to the lakeside； but； perhaps even moreremarkably； they then organized the site。 the leakeys鈥櫋xcavations revealed that there wereareas where axes were fashioned and others where blunt axes were brought to be resharpened。
olorgesailie was； in short； a kind of factory； one that stayed in business for a million years。
various replications have shown that the axes were tricky and labor…intensive objects tomake鈥攅ven with practice； an axe would take hours to fashion鈥攁nd yet； curiously； they werenot particularly good for cutting or chopping or scraping or any of the other tasks to whichthey were presumably put。 so we are left with the position that for a million years鈥攆ar； farlonger than our own species has even been in existence； much less engaged in continuous cooperative efforts鈥攅arly people came in considerable numbers to this particular site to makeextravagantly large numbers of tools that appear to have been rather curiously pointless。
and who were these people？ we have no idea actually。 we assume they were homoerectus because there are no other known candidates； which means that at their peak鈥攖heirpeak 鈥攖he olorgesailie workers would have had the brains of a modern infant。 but there is nophysical evidence on which to base a conclusion。 despite over sixty years of searching； nohuman bone has ever been found in or around the vicinity of olorgesailie。 however muchtime they spent there shaping rocks； it appears they went elsewhere to die。
鈥渋t鈥檚 all a mystery；鈥潯illani ngalli told me； beaming happily。
the olorgesailie people disappeared from the scene about 200；000 years ago when the lakedried up and the rift valley started to bee the hot and challenging place it is today。 butby this time their days as a species were already numbered。 the world was about to get itsfirst real master race； homo sapiens 。 things would never be the same again。
ww锛枫��
Goodbye
in the early 1680s； at just about the time that edmond halley and his friends christopherwren and robert hooke were settling down in a london coffeehouse and embarking on thecasual wager that would result eventually in isaac newton鈥檚 principia ； henry cavendish鈥檚weighing of the earth； and many of the other inspired and mendable undertakings thathave occupied us for much of the past four hundred pages； a rather less desirable milestonewas being passed on the island of mauritius； far out in the indian ocean some eight hundredmiles off the east coast of madagascar。
there； some forgotten sailor or sailor鈥檚 pet was harrying to death the last of the dodos； thefamously flightless bird whose dim but trusting nature and lack of leggy zip made it a ratherirresistible target for bored young tars on shore leave。 millions of years of peaceful isolationhad not prepared it for the erratic and deeply unnerving behavior of human beings。
we don鈥檛 know precisely the circumstances； or even year； attending the last moments of thelast dodo； so we don鈥檛 know which arrived first； a world that contained a principia or one thathad no dodos； but we do know that they happened at more or less the same time。 you wouldbe hard pressed； i would submit； to find a better pairing of occurrences to illustrate the divineand felonious nature of the human being鈥攁 species of organism that is capable of unpickingthe deepest secrets of the heavens while at the same time pounding into extinction； for nopurpose at all； a creature that never did us any harm and wasn鈥檛 even remotely capable ofunderstanding what we were doing to it as we did it。 indeed； dodos were so spectacularlyshort on insight； it is reported； that if you wished to find all the dodos in a vicinity you hadonly to catch one and set it to squawking； and all the others would waddle along to see whatwas up。
the indignities to the poor dodo didn鈥檛 end quite there。 in 1755； some seventy years afterthe last dodo鈥檚 death； the director of the ashmolean museum in oxford decided that theinstitution鈥檚 stuffed dodo was being unpleasantly musty and ordered it tossed on abonfire。 this was a surprising decision as it was by this time the only dodo in existence；stuffed or otherwise。 a passing employee； aghast； tried to rescue the bird but cou