- This is the scientific detective story of the age. Professor
Bryan Sykes tells how he and his colleagues discovered that modern Europeans
are descended from only a handful of women - the Seven Daughters of Eve.
Are you by any chance related? ___
-
- Where do I come from? How often have you asked yourself
that question? We may know our parents, even our grandparents; not far
beyond that, for most of us, the trail begins to disappear into the mist.
But each of us carries a message from our ancestors in every cell of our
body.
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- It is in our DNA, the genetic material that is handed
down from generation to generation. Within the DNA is written not only
our histories as individuals but the whole history of the human race. With
the aid of recent advances in genetic technology, this history is now being
revealed.
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- We are at last able to begin to decipher the messages
from the past. Our DNA does not fade like an ancient parchment; it does
not rust in the ground like the sword of a warrior long dead. It is not
eroded by wind or rain, nor reduced to ruin by fire and earthquake. It
is a traveller from an antique land who lives within us all.
-
-
- The history of our species, homo sapiens, is recorded
in the genes that trace our ancestry back into the deep past, way beyond
the reach of written records or stone inscriptions. These genes tell a
story that begins more than 100,000 years ago and whose latest chapters
are hidden within the cells of every one of us.
-
- As a practising scientist, I am very lucky to have been
around at the right time and able to take an active part in this wonderful
journey into the past that modern genetics now permits. I have found DNA
in skeletons thousands of years old and seen exactly the same genes in
my own friends. And I have discovered that, to my astonishment, we are
all connected through our mothers to only a handful of women living tens
of thousands of years ago.
-
- MY PART in this story began in the 1980s 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.
-
- I am based at the institute because I used to work on
inherited diseases of the skeleton, in particular on a horrible condition
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.
-
- It was through this work that, in 1986, I came to meet
Robert Hedges, who runs the carbon dating laboratory for archeological
samples in Oxford. Carbon dating involves measuring the decay of minute
traces of naturally radioactive carbon atoms within remains. Robert had
been thinking about ways of getting more information from the bones that
passed through his lab by pioneering a complex genetic process. He and
I put together a research proposal.
-
- We also advertised for research assistants - but got
no response at all. This meant we had to put back the start of the project
by a year. The delay proved to be a blessing in disguise - because, by
the time the project got going, a scientist in California called Kary Mullis
had dreamt up a way of making our work much easier. Mullis's brainwave
meant we could "amplify" in a test tube tiny amounts of DNA taken
from old bones. We also had a research assistant called Erika Hagelberg.
She was the only applicant. All we needed now was the bones.
-
- News came in during 1988 of an excavation in Abingdon,
a few miles south of Oxford. A new supermarket was going up and the diggers
had ploughed into a medieval cemetery. The local archeology service had
been given two months to excavate the site before developers moved back
in.
-
- Several skeletons lay half-exposed in the bright sunshine,
encrusted with orange-brown earth. Our prospects didn't look good: DNA
samples in the laboratory were always deeply frozen because everyone believed
they would be destroyed if they thawed.
-
- We were allowed to take away three thigh bones. We cut
out small segments of bone with a hacksaw, froze them in liquid nitrogen,
smashed them up into a powder, then soaked the powder in a chemical that
slowly took out the calcium over several days. This left a grey sludge.
We guessed this was proteins, bits of cells, maybe some fat - and, we hoped,
a few molecules of DNA.
-
- We got rid of the protein using an enzyme that digests
it, rather like the ones in a biological washing powder. Then we got rid
of the fat with chloroform. We cleaned what was left with phenol, a revolting
liquid that is the base for carbolic soap. What remained was a teaspoonful
of pale brown fluid that, theoretically at least, should contain the DNA
- if there was any.
-
- There would be at best only a few molecules, so we had
to use Mullis's new DNA amplification reaction to boost the yield. We had
to decide which gene to amplify and chose something called mitochondrial
DNA. This turned out to have special properties that make it absolutely
ideal for reconstructing the past; but in the first instance we chose it
simply because there was so much more of it than any other type of DNA.
Cells have upwards of a hundred times more of it than any other gene.
-
- So, into the reaction went all the chemical ingredients
necessary for amplifying mitochondrial DNA, plus a few drops of the precious
bone extract. To get the reaction to fire in the tube you need to boil
it, cool it, warm it up for a couple of minutes; then boil it again, cool
it, warm it up . . . and go on repeating this cycle at least 20 times.
-
- Modern genetics laboratories are full of machines for
doing this reaction automatically. But not then. Back in the 1980s the
only machine on the market cost a fortune, and there was no money for one
in our budget.
-
- The only way to do the reaction was to sit with a stopwatch
in front of three water baths, one boiling, one cold and one warm, and
move the test tube by hand from one bath to the next every three minutes.
Then do it again. And again. For 3 hours.
-
- I only tried it once. The reaction didn't work and I
was bored stiff. There had to be a better way. What about using an electric
kettle? I spent the next three weeks with wires, timers, thermostats, relays,
copper tubing, a washing machine valve and my kettle from home. In the
end I had a device that did all the right things. It boiled. It cooled.
And it warmed up. And it worked.
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- We could see that the machine (christened the Genesmaid,
after the tea-making device) had managed to get the amplification reaction
to work not only with a control experiment using modern DNA but also, very
faintly, with the Abingdon bone extract. By comparing its "sequence"
- fingerprint of DNA - to those published in scientific papers, it didn't
take us long to prove that the DNA was genuinely human. We had done it.
Here, in front of our very eyes, was the DNA of someone who had died hundreds
of years ago. It was DNA resurrected, literally, from the grave.
-
- Looking back, it is hard for me to believe that the research
set in motion by the recovery of DNA from those crumbling bones in the
Abingdon cemetery - the bones that looked so unpromising when I first saw
them half-buried in the earth - should lead over the following years to
such profound conclusions about the history and soul of our species.
-
- Like most scientific research, this was not a seamless
progression towards a well-defined goal. It was more like a series of short
hops, each driven as much by opportunity, personal relationships, financial
necessity and even physical injury as by any rational strategy. The research
just moved, a little bit at a time, mostly forwards, towards the next dimly
visible goal, informed by what had gone before but ignorant of what lay
ahead.
-
- At the time, though our result was a great triumph, strangely
enough it didn't feel like it. I think Erika and I were too heavily involved
in the details to appreciate the significance of what we had achieved.
Besides, by then we were not getting on at all well.
-
-
- Tension had been building for weeks because, for some
reason, Erika and I did not seem to be working together effectively. Our
ways would part, and many years later Erika and I would clash when she
challenged the scientific validity of my work.
-
- The next breakthrough after Abingdon man came on a sunny
day in September 1991 when two German climbers descending the 11,500ft
Finailspitze in the Italian Alps strayed into a gully. Sticking out of
the melting ice was the body of a man. What looked like an old-fashioned
ice pick lay nearby.
-
- The climbers assumed it was the body of a mountaineer
who had fallen into a crevasse perhaps 10 years previously. Only days later
did it dawn on everybody that this body was not tens or even hundreds but
thousands of years old.
-
- 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 carry out a minute examination.
-
- 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 in the Iceman. It was the 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.
-
- Carbon dating placed the Iceman 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.
-
- 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. We had got exactly the same DNA "sequence"
- the DNA equivalent of a fingerprint - from the Iceman as a 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.
-
- There were a number of press inquiries following the
publication of our scientific article about the Iceman, and I found myself
explaining how we had proved his European credentials. 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 inquired, in a tone that 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."
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- "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 prefix "LAB" meant it was either from someone working
in the laboratory or from a visitor or friend. When I checked against the
database of the volunteers, I could scarcely believe my luck.
-
- LAB 2803 was Marie Moseley, an Irish friend. This could
only mean one thing. Marie was a relative of the Iceman. For reasons which
I shall explain, there had to be an unbroken genetic link between Marie
and the Iceman's mother, stretching back more than 5,000 years and faithfully
recorded in the DNA.
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- Marie, a management consultant, lives just outside Bournemouth.
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. She is articulate, outgoing and 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 under the headline "Iceman's relative found in Dorset".
-
- One of the strangest and, at first, surprising things
about this story is that Marie began to feel something for the Iceman.
She had seen pictures of him being shunted 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 Marie
felt. It began to dawn on me that, if Marie could be genetically linked
to someone long dead, 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 archeologist friends found this proposition
completely foreign. 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, to one of only seven women.
These seven women are the direct maternal ancestors of virtually all 650m
modern Europeans. I was able to estimate how long ago, and approximately
where, all seven women had lived.
-
- As soon as I gave them names - Ursula, Xenia, Helena,
Velda, Tara, Katrine and Jasmine - they came to life. I know 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.
-
- I reckon 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 bougainvillea
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. Today just over 9% of native Europeans
are in the clan of Tara, living along the Mediterranean and the western
edge of Europe. They are particularly numerous in the west of Britain and
Ireland.
-
- Our most distant ancestor among the Seven Daughters of
Eve was Ursula (see panel), who lived 45,000 years ago. Xenia, a fair-haired
girl from the north European plains 25,000 years ago, was the direct
ancestor of not only 6% of modern Europeans but also about 1% of native
Americans. Helena, who lived at the mouth of the River Rhone 20,000
years ago, was the clan mother of 47% of modern Europeans. Velda, an inhabitant
of northwest Spain 17,000 years ago, was clan mother of about 5% of native
Europeans. About 6% are descended from Katrine, who lived 2,000 years later
in a great plain now covered by the northern Adriatic. One of her intermediate
descendants was the Iceman.
-
- The seventh daughter of Eve, Jasmine, lived near the
River Euphrates after the Ice Age. Her descendants, 17% of native Europeans,
are particularly common in Cornwall, Wales and the west of Scotland.
-
- Amazingly, we all carry this history in our genes, patterns
of DNA that have come down 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.
-
-
-
- © Professor Bryan Sykes 2001
-
- Extracted from The Seven Daughters of Eve by Bryan Sykes
to be published by Bantam Press on June 7 at £18.99. Copies can be
ordered for £16.99 from The Sunday Times Books Direct on 0870 165
8585; www.sundaytimesdirect.co.uk. Professor Sykes will lecture
at The Sunday Times Hay Festival on May 29 at 2.30pm. Festival
office: 01497 821 299 or www.hayfestival.co.uk. His own website is www.oxfordancestors.com
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