The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry
The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry
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Overview
In The Seven Daughters of Eve, he gives us a firsthand account of his research into a remarkable gene, which passes undiluted from generation to generation through the maternal line. After plotting thousands of DNA sequences from all over the world, Sykes found that they clustered around a handful of distinct groups. Among Europeans and North American Caucasians, there are, in fact, only seven.
Product Details
| ISBN-13: | 9781541463936 |
|---|---|
| Publisher: | Tantor Media, Inc. |
| Publication date: | 12/26/2017 |
| Edition description: | Unabridged |
| Product dimensions: | 5.30(w) x 7.40(h) x 0.60(d) |
About the Author
Read an Excerpt
Chapter One
ICEMAN'S RELATIVE FOUND IN DORSET
On Thursday 19 September 1991 Erika and Helmut Simon, two experienced climbers from Nuremberg in Germany, were nearing the end of their walking holiday in the Italian Alps. The previous night they had made an unscheduled stop in a mountain hut, planning to walk down to their car the next morning. But it was such a brilliantly sunny day that they decided instead to spend the morning climbing the 3, 516 metre Final spitze. On their way back down to the hut to pick up their ruck sacks they strayed from the marked path into a gully partly filled with melting ice. Sticking out of the ice was the naked body of a man.
Though macabre, such finds are not so unusual in the high alps, and the Simons assumed that this was the body of a mountaineer who had fallen into a crevasse perhaps ten or twenty years previously. The following day the site was revisited by two other climbers, who were puzzled by the old-fashioned design of the ice-pick that was lying nearby. Judging by the equipment, this alpine accident went back a good many years. The police were contacted and, after checking the records of missing climbers, their first thought was that the body was probably that of Carlo Capsoni, a music professor from Verona who had disappeared in the area in 1941. Only days later did it begin to dawn on everybody that this was not a modern death at all. The tool found beside the body was nothing like a modern ice-pick. It was much more like a prehistoric axe. Also nearby was a container made from the bark of a birch tree. Slowly the realization sank in that this body was not tens or even hundreds but thousands of years old. This was now an archaeological find of international importance.
The withered and desiccated remains of the Iceman, as he soon came to be known, were taken to the Institute of Forensic Medicine in Innsbruck, Austria, where he was stored, frozen, while an international team of scientists was assembled to carryout a minute examination of this unique find. Since my research team in Oxford had been the first in the world to recover traces of DNA from ancient human bones, I was called in to see whether we could find any DNA in the Iceman. It was the irresistible opportunity to become involved in such thrilling discoveries that had persuaded me to veer away from my career as a regular medical geneticist into this completely new field of science, which some of my colleagues regarded as a bizarre and eccentric diversion of no conceivable use or consequence.
By now, carbon-dating — measuring the decay of minute traces of naturally radioactive carbon atoms within the remains — had confirmed the great antiquity of the Iceman, placing him between 5, 000 and 5, 350 years old. Even though this was much older than any human remains I had worked with before, I was very optimistic that there was a good chance of success, because the body had been deep frozen in ice away from the destructive forces of water and oxygen which, slowly but surely, destroy DNA. The material we had to work with had been put in a small screw-capped jar of the sort used for pathology specimens. It looked awfully unremarkable: a sort of grey mush. When Martin Richards, my research assistant at the time, and I opened the jar and started to pick through the contents with a pair of forceps, it seemed to be a mixture of skin and fragments of bone. Still, though it might not have been much to look at, there was no obvious sign that it had begun to decompose, and so we set to work with enthusiasm and optimism. Sure enough, back in the lab in Oxford, when we put the small fragments of bone through the extraction process that had succeeded with other ancient samples, we did find DNA, and plenty of it.
In due course we published our findings in Science, the leading US scientific journal. To be perfectly honest, the most remarkable thing about our results was not that we had got DNA out of the body — by then this was a routine process — but that we had got exactly the same DNA sequence from the Iceman as an independent team from Munich. We had both shown that the DNA was clearly European by finding precisely the same sequence in DNA samples taken from living Europeans. You might think this was not much of a surprise, but there was a real possibility that the whole episode could have been a gigantic hoax, with a South American mummy helicoptered in and planted in the ice. The cold and intensely dry air of the Atacama desert of southern Peru and northern Chilehas preserved hundreds of complete bodies buried in shallow graves, and it would not have been hard for a determined hoaxerto get hold of one of them. The much damper conditions in Europe reduce a corpse to a skeleton very quickly, so if this was a hoax the body had to have come from somewhere else, probably South America. It may sound far-fetched; but elaborate tricks have been played before. Remember Piltdown Man. This infamous fossil had been `discovered' in a gravel pit in Sussex, England, in 1912. It had an ape-like lower jaw attached to a much more human-looking skull, and was heralded as the long sought-after `missing link' between humans and the great apes— gorillas, chimpanzees and orang-utans. Only in 1953 was it revealed to be a hoax, when radiocarbon analysis, the same technique that was later used to date the Iceman, proved beyond any doubt that the Piltdown skull was modern. The perpetrator, who has never been identified, had combined the lower jaw of an orang-utan with a human braincase and chemically stained them both to look much older than they really were. The long shadow cast by the Piltdown Man fraud lingers even to this day, so the idea that the Iceman might have been a hoax was very much at the front of everyone's mind.
There were a number of press enquiries following the publication of our scientific article about the Iceman, and I found myself explaining how we had proved his European credentials. Had it been a hoax, the DNA would have shown it. The closest matches would have been with South Americans and not with Europeans. But it was Lois Rogers from the Sunday Times who asked the crucial question.
`You say you found exactly the same DNA in modern Europeans. Well, who are they?' she enquired in a tone which told me she expected me to know the answer straight away.
`What do you mean, who are they? They are from our collection of DNA samples from all over Europe. '
`Yes, but who?' persisted Lois.
`I have no idea. We keep the identities of the donors on a separate file, and anyway, samples are always given on the basis of a strict undertaking of confidentiality. '
After Lois rang off, I switched on my computer just to see which samples matched up with the Iceman. LAB 2803 was one of them, and the series prefix `LAB' meant it was either from someone working in the laboratory or from a visitor or friend. When I checked the number against the database containing the names of the volunteers, I could scarcely believe my luck. LAB 2803 was Marie Moseley, and LAB 2803 had exactly the same DNA as the Iceman. This could only mean one thing. Marie was a relative of the Iceman himself. For reasons which I shall explain in detail in later chapters, there had to be an unbroken genetic link between Marie and the Iceman's mother, stretching back over five thousand years and faithfully recorded in the DNA.
Marie is an Irish friend, a management consultant from just outside Bournemouth in Dorset in southern England. Though not a scientist herself, she has an insatiable curiosity about genetics and had donated a couple of strands of her long red hair in the cause of science two years earlier. She is articulate, outgoing and very witty, and I was sure she could handle any publicity. When I rang to ask if she would mind if I gave her name to the Sunday Times she agreed at once, and the next edition carried a piece on her under the headline `Iceman's relative found in Dorset'.
For a few weeks after that, Marie became an international celebrity. Of all the headlines that followed, I liked the one from the Irish Times best of all. Their reporter had asked Marie if she had been left anything by her celebrated predecessor. Shockingly, she revealed that she had not; so the story appeared as `Iceman leaves one of our own destitute in Bournemouth'.
One of the strangest and, at first, surprising things about this story, and the reason I tell it here, is that Marie began to feel something for the Iceman. She had seen pictures of him beings hunted around from glacier to freezer to post-mortem room, poked and prodded, opened up, bits cut off. To her, he was no longer just the anonymous curiosity whose picture had appeared in the papers and on television. She had started to think of him as a real person and as a relative — which is exactly what he was.
I became fascinated by the sense of connection that Marie had felt between herself and the Iceman. It began to dawn on me that if Marie could be genetically linked to someone long dead, thousands of years before any records were kept, then so could everyone else. Perhaps we only needed to look around us, at people alive today, to unravel the mysteries of the past. Most of my archaeologist friends found this proposition completely foreign to them. They had been brought up to believe that one could understand the past only by studying the past; modern people were of no interest. Yet I was sure that if DNA was inherited intact for hundreds of generations over thousands of years, as I had shown by connecting Marie and the Iceman, then individuals alive today were as reliable a witness to past events as any bronze dagger or fragment of pottery.
It seemed to me absolutely essential to widen my research to cover modern people. Only when much more was known about the DNA of living people could I hope to put the results from human fossils into any sort of context. So I set out to discover as much as possible about the DNA in present-day Europeans and people from many other parts of the world, knowing that whatever I found would have been delivered to us direct from their ancestors. The past is within us all.
My research over the intervening decade has shown that almost everyone living in Europe can trace an unbroken genetic link, of the same kind that connects Marie to the Iceman, way back into the remote past, to one of only seven women. These seven women are the direct maternal ancestors of virtually all 650 million modern Europeans. As soon as I gave them names — Ursula, Xenia, Helena, Velda, Tara, Katrine and Jasmine — they suddenly came to life. This book tells how I came to such an incredible conclusion and what is known about the lives of these seven women.
I know that I am a descendant of Tara, and I want to know about her and her life. I feel I have something in common with her, more so than I do with the others. By ways which I will explain, I was able to estimate how long ago, and approximately where, all seven women had lived. I reckoned that Tara lived in northern Italy about 17, 000 years ago. Europe was in the grip of the last Ice Age, and the only parts of the continent where human life was possible were in the far south. Then, the Tuscan hills were a very different place. No vines grew; no bougain villaea decorated the farmhouses. The hillsides were thickly forested with pine and birch. The streams held small trout and crayfish, which helped Tara to raise her family and held the pangs of hunger at bay when the menfolk failed to kill a deer or wild boar. As the Ice Age loosened its grip, Tara's children moved round the coast into France and joined the great band of hunters who followed the big game across the tundra that was northern Europe. Eventually, Tara's children walked across the dry land that was to become the English Channel and moved right across to Ireland, from whose ancient Celtic kingdom the clan of Tara takes its name.
Soon after the conclusions of my research were published, news of these seven ancestral mothers began to appear in newspapers and on television all round the world. Writers and picture editors used their imagination in finding contemporary analogues: Brigitte Bardot became the reincarnation of Helena;Maria Callas was Ursula; the model Yasmin le Bon was linked, naturally, with Jasmine; Jennifer Lopez became Velda. So many people rang us to find out which one they were related to that we had to set up a website to handle the hundreds of enquiries. We had stumbled across something very fundamental; something we were only just beginning to understand.
This book tells the story behind these discoveries and their implications for us all, not just in Europe but all over the world. It is a story of our common heritage and our shared forebears. It takes us from the Balkans in the First World War to the far islands of the South Pacific. It takes us from the present time back to the beginnings of agriculture and beyond, to our ancestors who hunted with the Neanderthals. Amazingly, we all carry this history in our genes, patterns of DNA that have comedown to us virtually unchanged from our distant ancestors — ancestors who are no longer just an abstract entity but real people who lived in conditions very different from those we enjoy today, who survived them and brought up their children. Our genes were there. They have come down to us over the millennia. They have travelled over land and sea, through mountain and forest. All of us, from the most powerful to the weakest, from the fabulously wealthy to the miserably poor, carry in our cells the survivors of these fantastic journeys — our genes. We should be very proud of them.
My part in this story begins at the Institute of Molecular Medicine in Oxford, where I am a professor of genetics. The Institute is part of Oxford University, though geographically and temperamentally removed from the arcane world of the college cloisters. It is full of doctors and scientists who are working away applying the new technologies of genetics and molecular biology to the field of medicine. There are immunologists trying to make a vaccine against AIDS, oncologists working out how to kill tumours by cutting off their blood supply, haematologists striving to cure the inherited anaemias which disable or kill millions each year in the developing world, microbiologists unravelling the secrets of meningitis and many others. It is an exciting place to work. I am based at the Institute because I used to work on inherited diseases of the skeleton, in particular on a horrible condition called osteogenesis imperfecta, better known as brittle bone disease. Babies born with the most severe form of this disease sometimes have bones so weak that when they take their first breath, all the ribs fracture and they suffocate and die. We were researching the cause of this tragic disease and had traced it to tiny changes in the genes for collagen. Collagen is the most important and abundant protein in bones and it supports them in much the same way as steel rods strengthen reinforced concrete. It made sense that if collagen failed because of a fault in the gene, the bones would break. The research involved finding out a lot about the way collagen and its genes varied in the general population — and it was through this work that, in 1986, I came to meet Robert Hedges.
Robert runs the carbon-dating laboratory for archaeological samples in Oxford. He had been thinking about ways of getting more information from the bones that passed through his lab, aside from just dating them by the radiocarbon method. Collagen is the main protein not only in living bones but also in dead ones, and it is the carbon in the surviving collagen that is used to date them. Robert wondered if there was any genetic information in these surviving fragments of ancient collagen, so he and I put together a research proposal to study them. Collagen, being a protein, is made of units called amino-acids, arranged in a particular sequence. As we shall see in the next chapter, the sequence of amino-acids in collagen, and all other proteins for that matter, is dictated by the DNA sequence of their genes. We hoped to discover the DNA sequence of the ancient collagen genes indirectly by determining the order of amino-acids in the fragments of protein that survived in Robert's old bones. We advertised for research assistants several times but got no response at all. We would have expected a flood of applications for a regular genetics post, and put this zero interest down to the unusual nature of the project. Disappointingly few scientists want to venture from the mainstream field of research at an early stage of their careers. For us, this lack of a recruit meant we had to put back the start of the project by a year. Although very frustrating at the time, the delay proved to be a blessing in disguise — because, before the project got going, news came in of a new invention. A US scientist in California called Kary Mullis had dreamed up a way of amplifying tiny amounts of DNA — under perfect conditions, as little as a single molecule— in a test tube.
One warm Friday night in 1983 Mullis was driving along Highway 101 by the ocean; according to his account of events,`the night was saturated with moisture and the scent of flowering buckeye. As he drove, he was talking to his girlfriend, seated beside him, about some of the ideas he had been pondering to do with his work at a local biotech company. Like everyone else in the genetic engineering business, he was making copies of DNA in test tubes. This was a slow process because the molecules had to be copied one at a time. DNA is like a long piece of string, and the copying started at one end and finished at the other. Then it started at the beginning again and you got another copy. He was talking out loud about this and suddenly realized that if, instead of starting the copying at one end only, you started at both ends you would start what would effectively be a sustainable chain reaction. You would no longer just be making copies of the original but copies of copies, doubling the number at every cycle. Now, instead of two copies after two cycles and three copies after three cycles, you would double up after each cycle, producing two, four, eight, sixteen, thirty-two, sixty-four copies in six cycles instead of one, two, three, four, five and six. After twenty cycles you would have not just twenty copies but a million. It was a real`Eureka' moment. He turned to his girlfriend to get her reaction. She had fallen asleep.
This invention, for which Kary Mullis rightly won the Nobel prize for Chemistry in 1993, genuinely revolutionized the practice of genetics. It meant that you could now get an unlimited amount of DNA to work on from even the tiniest piece of tissue. A single hair or even a single cell was now all that was needed to produce as much DNA as you could ever want. The impact of Mullis's brain wave on our bone project was simply that I decided to forget about working on the collagen protein, which would have been horrendously difficult, and use the newly invented chain reaction to amplify what, if anything, was left of the DNA in the ancient bones. If it worked, then we would get vastly more information from the DNA than we would ever have got from the collagen. We would be going directly for the DNA sequence itself, rather than inferring it from the amino-acids. Much more importantly, we would be able to study any gene, not just the ones that controlled collagen.
At last we got an answer to our advertisement for a research assistant, and Erika Hagelberg joined the team. We were obviously not going to get anyone with previous experience in working with ancient DNA, because it had never been done before, but Erika's degree in biochemistry, combined with research posts in homoeopathy and in the history of medicine, reflected a combination of a solid scientific training and the catholic interests which suited the project. Besides, she was the only applicant. Now we needed some very old bones.
News came in during 1988 of an excavation going on in Abingdon, a few miles south of Oxford. A new supermarket was going up and the mechanical diggers had ploughed into a medieval cemetery. The local archaeology service had been given two months to excavate the site before the developers moved back in, so when Erika and I arrived, it was buzzing with activity. It was a hot and brilliantly sunny day and dozens of field assistants, stripped down to the bare essentials, were dotted all round the site scraping at the earth with trowels, rummaging around in deep pits or wading through water-filled trenches. Several skeletons lay half-exposed, encrusted with orange-brown earth, criss-crossed by strings which marked out a reference grid. As we gazed down at them, our prospects didn't look at all promising. Having worked with DNA for several years, I was trained to treat it with respect. DNA samples were always stored frozen at 70º below zero, and whenever you took DNA out of the freezer you were taught always to keep it in an ice bucket. If you forgot about it and the ice thawed then you had to throw the DNA out because, so everyone assumed, it would have degraded and been destroyed. No-one imagined it would last for more than a few minutes on the laboratory bench at room temperature, let alone buried underground for hundreds or even thousands of years.
(Continues. . . )
Excerpted from THE SEVEN DAUGHTERS OF EVE by BRYAN SYKES. Copyright © 2001 by Bryan Sykes. Excerpted by permission. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.