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ile studying betaglobingenes in modern people； found two variants that are mon among asians and theindigenous people of australia； but hardly exist in africa。 the variant genes； she is certain；arose more than 200；000 years ago not in africa； but in east asia鈥攍ong before modern homosapiens reached the region。 the only way to account for them is to say that ancestors ofpeople now living in asia included archaic hominids鈥攋ava man and the like。 interestingly；this same variant gene鈥攖he java man gene； so to speak鈥攖urns up in modern populations inoxfordshire。
confused； i went to see harding at the institute； which inhabits an old brick villa onbanbury road in oxford； in more or less the neighborhood where bill clinton spent hisstudent days。 harding is a small and chirpy australian； from brisbane originally； with the rareknack for being amused and earnest at the same time。
鈥渄on鈥檛 know；鈥潯he said at once； grinning； when i asked her how people in oxfordshireharbored sequences of betaglobin that shouldn鈥檛 be there。 鈥渙n the whole；鈥潯he went on moresomberly； 鈥渢he genetic record supports the out…of…africa hypothesis。 but then you find theseanomalous clusters； which most geneticists prefer not to talk about。 there鈥檚 huge amounts ofinformation that would be available to us if only we could understand it； but we don鈥檛 yet。
we鈥檝e barely begun。鈥潯he refused to be drawn out on what the existence of asian…origin genes in oxfordshire tells us other than that the situation is clearly plicated。 鈥渁ll we cansay at this stage is that it is very untidy and we don鈥檛 really know why。鈥�
at the time of our meeting； in early 2002； another oxford scientist named bryan sykes hadjust produced a popular book called the seven daughters of eve in which； using studies ofmitochondrial dna； he had claimed to be able to trace nearly all living europeans back to afounding population of just seven women鈥攖he daughters of eve of the title鈥攚ho livedbetween 10；000 and 45；000 years ago in the time known to science as the paleolithic。 to eachof these women sykes had given a name鈥攗rsula； xenia； jasmine； and so on鈥攁nd even adetailed personal history。 （鈥渦rsula was her mother鈥檚 second child。 the first had been taken bya leopard when he was only two。 。 。 。鈥潱﹚hen i asked harding about the book； she smiled broadly but carefully； as if not quitecertain where to go with her answer。 鈥渨ell； i suppose you must give him some credit forhelping to popularize a difficult subject；鈥潯he said and paused thoughtfully。 鈥渁nd thereremains the remote possibility that he鈥檚 right。鈥潯he laughed； then went on more intently：
鈥渄ata from any single gene cannot really tell you anything so definitive。 if you follow themitochondrial dna backwards； it will take you to a certain place鈥攖o an ursula or tara orwhatever。 but if you take any other bit of dna； any gene at all； and traceit back； it will takeyou someplace else altogether。鈥�
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 ki