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Scotland's DNA: Who do you think you are - Part One

DNA – deoxyribonucleic acid – is the basis of life. Its molecular structure was discovered in 1953, revealing how it carries all the genetic information needed for organisms to live and reproduce.

Scientists describe it in sequences of letters, and humans inherit three billion from each of their parents. As generations move from place to place, distinctive DNA markers are carried by each and every one of us. In a programme of pioneering research at Edinburgh University, Dr Jim Wilson has been gathering samples of DNA from Scots across the country and this week, in a new book by Alistair Moffat, and in a series of features in The Scotsman, we discover what his innovative work has revealed – and where the Scots came from. Day 1 looks at our origins.

ON THE soft clay floor of a cave in southern France the footprints of a little boy were found. Scorchmarks and smudges on the walls showed that he had lit the darkness with a torch and felt his way forward with his free hand. The height of the marks suggested that the boy was no more than ten years old, but other evidence told a remarkable story. He had entered the cave 27,000 years ago and was the last to see it before the entrance was closed up and the cave faded out of memory. Not until 1994 was it rediscovered.

Alone, the little boy had come to look upon magic. As his torch guttered in the air currents, he held it up high to see the magical paintings. Across the walls of the cave and its chambers wild horses galloped, viciously horned cattle charged and herds of reindeer gathered. And the prehistoric painters did not forget their ferocious predators; lions, hyenas, panthers and giant cave bears. Like them, the little boy may be lost to history. Unlike them, as we now know from new genetic evidence, his descendants – twice as many people as will fill Ibrox and Parkhead this Saturday - are all around us in modern Scotland.

The gallery of beautifully realised images in the Chauvet cave in the Ardche, France, is a record of a lost world, the oldest surviving figurative paintings in the world, but it is not unique. On either side of the Pyrenees more than 350 caves have been found to have images on their walls. And many are stunning works of art. Their discovery has transformed perceptions of prehistoric peoples. Instead of ragged primitives, here were artists able to make the most convincing naturalistic images and even to understand rudimentary perspective.

Nothing as vibrant would be painted again until the Italian Renaissance. When Pablo Picasso saw the paintings in the famous cave at Lascaux, he declared: "In 12,000 years we have learned nothing!".

Far to the north Scotland lay sleeping under a crushing blanket of ice, in places more than a kilometre thick. In a blinding white and bitterly cold landscape nothing and no-one could live. Southern England and northern Europe were a sterile, windswept polar tundra. Only in the warmer south could human beings and animals survive. To archaeologists the painted caves were part of the Ice Age Refuges, where life in Europe overwintered, and to geneticists they are the vivid and vital source of our early DNA.

Fifteen thousand years after the awestruck little boy had made his pilgrimage to Chauvet, his descendants left the darkness of the Refuges and began to walk northwards. As the ice melted, glaciers groaned and splintered and the cold retreated, some of them walked into the empty peninsula of northern Europe that was to become Scotland. The boy and the painters who amazed him are not lost, their DNA lives on in modern Scotland. More than 150,000 Scottish men are the direct descendants of the people of the Ice Age Refuges. Theirs is one of the founding lineages, that of the pioneers, the first to walk their lives under these big skies, the first people who could call themselves Scots.

DNA is inherited from our parents. Each of us has six billion letters of DNA, three billion from our fathers and three billion from our mothers. The letters are passed on in a certain sequence but when mistakes in genetic copying occur over time, these changes or mutations are labelled markers. And they too are then passed on. Human DNA is very homogenous (95 per cent of our DNA is identical to that of chimpanzees) and these mutations or markers are tiny, but their identification does allow population movement in history to be much more clearly understood than it was.

M284 is a Y-chromosome marker carried and passed on by men, and it is the marker that walked northwards from the Refuges. From small family bands hunting and gathering in the tangle of the prehistoric wildwood, the marker multiplied and is now carried by 6 per cent of Scotsmen, 150,000 in all.

All Scots are immigrants. The fascinating questions are: where did they come from, when did they arrive, to whom are they related, and – especially in the long era before historical records – is it possible to glean any sense of what they were like? As the research into the cave painters of the Refuges shows, geneticists have recently discovered at least partial answers to all of these. But it is vital to understand something about absolute origins.

All Scots are descended from Africans. And it was studies of mitochondrial DNA, what is passed on only by mothers through their daughters, that revealed this clear and absolute conclusion. A New Zealander of Scots descent, Professor Allan Wilson, saw how individuals, and not just populations, were related to each other through their DNA. And because these links were longest in Africa where many more markers had evolved than anywhere else, Wilson and his team made the earth-shattering announcement that the whole human race had originated there. This caused uproar. Most scientists believed that Homo sapiens had descended from various ancestors around the world: the Chinese were thought to be the children of Peking Man, the South East Asians came from Java Man and Europeans from Neanderthals. The discovery that modern humans had walked out of Africa to populate the whole of the rest of the world was sensational and it made headlines, but Wilson's meticulously researched, thoroughly scientific conclusions are now accepted. Our ancestors did walk out of Africa – but what made them leave?

Seventy thousand years ago the world was suddenly changed. The super-colossal eruption of Mount Tambora, a volcano in the Indonesian archipelago, triggered a severe and lengthy nuclear winter all over the world. Only a remnant of Homo sapiens, perhaps only 5,000, survived in the rift valleys of East Africa. For some unknowable reason, perhaps a severe shortage of food, a tiny group, no more than 300, decided to leave the valleys and make a life beyond them. It was an immense, epic journey, one which would ultimately populate the whole of the rest of the world.

When the exodus bands reached the Horn of Africa, they crossed to the Indian Ocean coast of the Arabian peninsula. The Bab el Mandeb, the Gate of Tears, that leads into the Red Sea is only 10 miles wide between modern Djibouti and the Yemen but even over that distance, boats will have been needed to gain the farther shore.

Over each new horizon they carried the secrets of their DNA inside them, and as they crossed rivers and mountain ranges, it seems that only two motherline lineages carrying mtDNA and two fatherline lineages carrying Y chromosome DNA survived the privations of their great journey. As the pioneers reached the Persian Gulf, some appear to have swung north to the lands watered by the rivers Tigris and Euphrates. The region that used to be known as Mesopotamia was the place from where the Homo sapiens, eventually began to move into Europe and mid-Asia. Many thousands of years after their ancestors left the rift valleys, some of these people probably reached Scotland. But then they were driven south by the onset of the last Ice Age, and it erased any trace of their presence. But in a historical paradox it was the ice that eventually allowed a second founding lineage to come to Scotland.

One of the very oldest Y lineages in Scotland leads the eye east rather than due south to the caves of France and Spain. M423 is carried by around 20,000 Scots men and it is another founding lineage. Remarkably, M423 is shared by between 30 per cent and 40 per cent of Croatian and Bosnian men, and appears to have originated in the Danube basin. This was one of the points of entry into Europe for the pioneering bands who left the rift valleys of Africa and came north through Mesopotamia. A subgroup of the M423 lineage appears at the western end of the North German Plain and then reappears on the British shores of the North Sea. It is as though there is a missing historical step.

In early 2001 researchers at Birmingham University looked at a dim, grainy image and were amazed at what they could make out. Picked out in green and yellow against a black background was the course of an ancient and unknown river. Fed by a network of tributaries, it seemed to run for about 30 miles. The lost river had been found by seismic reflection, a version of the geophysical surveys done by archaeologists on sites where the remains of buildings or earthworks are thought to be buried. But the green images were different. Supplied by the oil and gas industry, they were part of a vast survey of the bed of the North Sea and what lay under it. The ancient river had once flowed through the hills and valleys of a mysterious world, a huge part of Europe which has disappeared beneath the waves. Researchers have dubbed it Doggerland, after the Dogger Bank.

What the seismic reflection survey supplied was not only confirmation but detail. Much of Doggerland was an immense and watery plain. Many lost rivers meandered through it, creating oxbows, wide deltas and large areas of wetland. Some of these flowed into a huge inland sea, what the undersea surveyors called the Outer Silver Pit. The Dogger Hills were a rare area of high ground. In the samples of submarine peat brought to the surface for analysis, pollen traces have confirmed birch, willow, hazel, oak and chestnut trees. It is thought that deer, boar, bears, beavers and many other animals browsed the lush vegetation of the Doggerland woods while its wetland will have been home to many species of birds. For hunter-gatherer-fishers it was a very good place to live and hundreds of family bands will have thrived there. They were the ancestors of some of the earliest Scots.

At the zenith of the last ice age when bitter hurricanes tore down from the summits of gigantic spherical ice-domes, northern Europe was crushed. Under the great weight of cubic kilometres of ice, the crust of the Earth had been depressed so much in the north that the land to the south had risen. Like a fat man sitting on one end of a bolster, the ice had produced an effect called a forebulge. And so when the ice began to retreat, a vast area of dry land was revealed. It was Europe's lost sub-continent, an Atlantis in the east. But as the Earth's crust bounced back after the ice melted in Scandinavia, Doggerland became slowly submerged and by 4,000BC it had all but disappeared beneath the waves. Nevertheless the new North Sea, the Atlantic and the Channel did not deter immigrants, and the pioneers from the east and the south who first saw Scotland would soon be joined by waves of more peoples, the ancestors of most of us.

• The Scots: A Genetic Journey by Alistair Moffat and Dr Jim Wilson is published on 5 March. A radio series based on the book is broadcast on BBC Radio Scotland every Wednesday (3:30pm) until 23 March, repeated on Sundays (10:30am).

Case study

• The son of emigrants, Ian Carswell lives in Sydney, Australia. He carries the M284 marker from the Ice Age Refuges and his ancestors were among the first to see Scotland after the retreat of the ice. He shares it with 6 per cent of the Scottish population, 150,000 men.

• "When I first got my results I was very surprised that they were somewhat out of the ordinary. I had expected they would be much the same as everyone else's," he says. "But I was very pleased that I had discovered more about my father's family.

"Our convict forebear who settled in Tasmania had a well-documented career there but there were few clues about his previous life. My father told me we were originally from Dunlop in Renfrewshire and we come from a long line of farmers and cattle rustlers. As a boy, I was always a bit disappointed with this, but it's pretty much the bones of the matter, as it turns out."

• Over the past four centuries increasing numbers of Scots emigrants have carried many of our native markers overseas. In the future it may be that lineages that have died out in Scotland will flourish in foreign fields.

 
 
 

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