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ay that ancestors ofpeople now living in asia included archaic hominids—java man and the like。 interestingly；this same variant gene—the java man gene； so to speak—turns 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。
“don’t know；” she said at once； grinning； when i asked her how people in oxfordshireharbored sequences of betaglobin that shouldn’t be there。 “on the whole；” she went on moresomberly； “the genetic record supports the out…of…africa hypothesis。 but then you find theseanomalous clusters； which most geneticists prefer not to talk about。 there’s huge amounts ofinformation that would be available to us if only we could understand it； but we don’t yet。
we’ve barely begun。” she 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。 “all we cansay at this stage is that it is very untidy and we don’t really know why。”
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—the daughters of eve of the title—who 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—ursula； xenia； jasmine； and so on—and even adetailed personal history。 （“ursula was her mother’s second child。 the first had been taken bya leopard when he was only two。 。 。 。”）when i asked harding about the book； she smiled broadly but carefully； as if not quitecertain where to go with her answer。 “well； i suppose you must give him some credit forhelping to popularize a difficult subject；” she said and paused thoughtfully。 “and thereremains the remote possibility that he’s right。” she laughed； then went on more intently：
“data 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—to 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。”
it was a little； i gathered； like following a road randomly out of london and finding thateventually it ends at john o’groats； 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。 “no single gene is ever going to tell you the whole story；” she said。
so genetic studies aren’t to be trusted？
“oh you can trust the studies well enough； generally speaking。 what you can’t trust are thesweeping conclusions that people often attach to them。”
she thinks out…of…africa is “probably 95 percent correct；” but adds： “i 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’s never going to be easy to sort out。”
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。 “in the process；” noted the nature article； “largeamounts of modern human dna would have been transferred to the skull；” rendering ituseless for future study。 i asked harding about this。 “oh； it would almost certainly have beencontaminated already；” she said。 “just 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。”
so should such claims be treated dubiously？ i asked。
harding nodded solemnly。 “very；” she 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’s 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 huma