by Bryan Sykes
Repeating the same calculations for the other six clans, we arrive at estimates for the ages of the other clan mothers. The clan with the greatest number of additional mutations on top of the clan mother’s signature sequence is Ursula’s. Hers is therefore the oldest of the seven clans. The average number of extra mutations in the clan is 2.75, and factoring in the mutation rate, this means that Ursula herself lived 45,000 years ago. Xenia is the next oldest at 25,000 years, Helena next at 20,000 years, then Velda and Tara both at 17,000 years, Katrine slightly younger at 15,000 years and finally Jasmine at 10,000 years ago.
Working out how long ago these women lived was a big step to discovering what their lives were like. Now I knew when they lived, could I discover where? I used three tests to find out. First, knowing the current whereabouts of the clan throughout Europe, I discovered where the clan was concentrated, reasoning that even after so many thousands of years, this might still be close to its origin. However, more important was to plot where the clan had accumulated the most additional mutations. The reasoning here was that the clan would have had longest to ‘age’ close to its origin, where the clan mother herself lived. To give you an example, the clan of Velda reaches its highest frequency in two places – northern Spain and among the Saami of northern Scandinavia. But it is far more varied, in the sense that it has accumulated far more extra mutations, in Spain than in Lapland. So I placed Velda herself in northern Spain, rather than in the far north of Norway and Sweden. Which brings me on to the third test. The location of the clan mother has to have been habitable at the time. In Velda’s case, we know from the archaeological records that people were living in northern Spain 17,000 years ago, the date estimated from the additional mutations in the clan, but they were certainly not living in northern Scandinavia, which was under several kilometres of ice. By the same process, the other clan mothers were located to Greece (Ursula), the Caucasus mountains (Xenia), southern France (Helena), northern Italy (Katrine and Tara) and finally Syria in the Middle East (Jasmine).
With information from climate records and the archaeological evidence, I was able to find out what conditions must have been like for these women living at these locations at those times in the past. I discovered what their landscape was like, what sort of diet they had, what age they reached and, armed with this information, I wrote imagined lives for them.
Since they were published, the response has been both surprising and intriguing. My laboratory was overwhelmed by requests from all over the world from people who wanted to know from which of these women they were themselves descended. We had already repeated the process worldwide and found a total of thirty-six equivalent clans, so we could deal with requests from anywhere. We could not possibly handle this demand in the lab, if only because we were prevented from carrying on any commercial activities by the rules of our principal sponsors, the Wellcome Trust. So the University rapidly formed a spinoff company, Oxford Ancestors, to perform this service. But that is of only passing interest compared to the quite extraordinary underlying emotion that the concept clearly aroused. It proved to me that to many people, of which I am one, the idea that within each of our body cells we carry a tangible fragment from an ancestor from thousands of years ago is both astonishing and profound. That these pieces of DNA have travelled over thousands of miles and thousands of years to get to us, virtually unchanged, from our remote ancestors still fills me with awe, and I am not alone. One unexpected effect is that when two people discover that they are both in the same clan, they really do feel like close relatives, like cousins or siblings. I have seen this happen time and again, and indeed on the Oxford Ancestors website one of the most popular activities is discovering genetic relatives and then swapping personal information and often finding uncanny similarities of personality and circumstance. Even if this is all retrospective wisdom, after the test rather than before, the strength of feeling is very strong. There are even Jasmine parties organized by members of the clan.
I recently tested the DNA of our Vice-Chancellor, the executive head of Oxford University – I rarely travel anywhere without a DNA sampling brush – and discovered that he and I are not only in the same clan of Tara, but have exactly the same mDNA sequence 126, 292, 294. This means that as well as a common ancestor 17,000 years ago in Tara herself, we must share a much more recent maternal ancestor. I don’t know who that is, but the point of the story is that, for better or worse, I feel now very differently about the Vice-Chancellor. So much so that, were we to have a severe disagreement, it would be hard for me to take it quite so seriously. It would be like arguing with my cousin.
A few years later, the same treatment became possible for the Y-chromosome. The details of the genetic changes were slightly different, and we will see how in a later chapter, but the principle remains the same. Whereas there are seven maternal clans which predominate in western Europe, there are only five principal paternal clans defined by the Y-chromosome. Each of these began with just one man, but for reasons that will become clear, it is much harder to know when and where they might have lived.
7
THE NATURE OF THE EVIDENCE
The collection phase of the Isles research project began ten years ago, in 1996, under the title of the Oxford Genetic Atlas Project. I obtained ethical permission to collect DNA samples from volunteers with the specific objective of discovering more about our genetic history. Over the next few years, my research team and I worked our way all over the Isles. We collected over 10,000 DNA samples and travelled over 80,000 miles by train, plane, boat, car and bus. Eventually I had to draw a line under the collection phase and concentrate on distilling some meaning from the thousands of DNA samples that now lay crowded in the lab freezers. We had been putting them through the analytical procedures more or less as they were being collected, converting the drab white threads of DNA into the sequences which would, or so we dearly hoped, hold the secrets of the ancient people of the Isles. Displayed on a computer screen they looked detached, dead – nothing like the talismans of ancient histories that I hoped they would become.
It took a lot of mental effort constantly to remind myself that every single one of these strings of letters and numbers represented the journey of an ancestor. A journey that at one stage almost certainly involved a sea crossing in a fragile craft to landfall on the Isles and an uncertain future. Fantastic though it sounds, it had to be true that each one of the thousands upon thousands of read-outs that flashed from the analyser to the computer in a fraction of a second had been carried across the sea in the cells of an ancestor. How could I get these mute listings to tell me their stories? How could I get them to sing? If only, I thought one day, I could read in the letters of the genetic code the language of the bearer. How wonderful that would be – and how much easier than the task that lay ahead. If, just by looking, I could recognize a Gaelic word or a Saxon spelling somewhere in the sequence of DNA letters. But the genes were stubbornly silent, oblivious to the tongues of their bearers.
Mathematicians have devised a whole array of statistical tests to sieve through DNA results, mechanically and without feeling. Indeed, most scientific papers on this kind of genetics spend at least half the time agonizing over what is the correct statistical treatment. It is necessary, if only to get results published, to know how to do this and fortunately we had in the lab several people skilled in the art. They, in particular Eileen, Jayne and Sara, put the accumulating genetic data through their paces. They ran Hudson tests, Mantel tests, distance-based clustering analyses, drew genetic matrices based on Fst and Nei’s D, performed spatial auto-correlation tests and many more. Here are some of the results that came screaming out of the computer. It is a set of genetic comparisons from mitochondrial DNA between the four regions of the Isles.
Ireland/Wales 0.0726741243702487
Ireland/Scotland 0.0625191372016303
Ireland/England 0.1170327104307371
Wales/Scotland 0.0662071306520113
Wales/England 0.0980420127467
032
Scotland/England 0.1023741618921030
You do not need to know what these mean, and I hope you do not want to. Even as I write them down, I can feel I am being drawn away from the real lives of these genes into some grey underworld where everything becomes a number. The genes are submitting to this cruel procedure, but they will never sing again. Now they are processed into numbers, with so many decimal places that they assume an importance way above their true worth. It feels as though I have handed them on to a windowless world which has severed any contact with the sea and the wind. Once a number is produced, something, perhaps everything, of value has been lost. Like so many tabulations, the numbers disguise individual stories of heroism and betrayal, triumph and defeat, and force them into bleak summaries. This is no way to treat our ancestors and you will be glad that I shall not insult them, or you, in this way again.
Since every ancestor was an individual, I was determined to treat the DNA sequences as individuals. Each one had, at some time, set off from some distant land and stepped ashore on the Isles, soaked with salt spray and red-faced from the cold. I decided that, if I possibly could, I would not treat these as anything but individual journeys undertaken with deliberate purpose and not to be grouped together in clumsy approximations. I covered the walls around my desk with photographs of the coast and the sea, of the Isles from the savage Atlantic to the smooth sands of Kent. Whenever I was tempted to revert to orthodox analysis I would glance upwards and remember to tread more carefully.
Finally, I had nearly 6,000 different pieces of genetic information from volunteers all over the Isles, each one linked to a geographical origin. By the time I came to write Blood of the Isles, I could add in another 25,000 genetic messages from among the customers of Oxford Ancestors. I contacted colleagues whom I knew had similar genetic information from the Isles and from other parts of Europe. I trawled all the relevant publications for material. When I finally settled down to listen to the music of the genes I had over 50,000 DNA sequences to work with.
For two solid weeks over Christmas I sat down to get to know these details. Fortunately, the weather was awful. It was raining constantly and was very, very windy. I live close to a sea loch in Skye and, when the wind is strong and in the south-west, blowing straight in from the North Atlantic, it descends in howling gusts from the Cuillin Hills. These winds tumble off the main ridge of the mountains and roll down the loch, pulling the top layer of water into the air in spiral twists of spray. The oddest thing about these winds is their intermittence. The air is calm, windless and then you hear an approaching roar and it is upon you and so strong it is almost impossible to stand upright. Then, after five minutes’ battering, it is gone. After another few minutes the sequence begins all over again. The alternating spells of chaos and calm can go on for hours. Hours well suited to going through thousands of sequences one by one, giving each one a different name and a different number. The coal fire burns well and the smoke is only very rarely forced back down the chimney.
This is how I got to know the data. Thanks to a mapping program written by a colleague, I could quickly place any selection of DNA sequences on a map of the Isles. As I did this I soon noticed that some DNA sequences were found in all parts of the Isles, while others were very localized. For instance, I had found one particular mDNA sequence in the clan of Tara four times in Skye, once in Lewis in the Western Isles and once in Glasgow – and nowhere else in the world. When I looked up in my records where on Skye the four people lived, I saw they came from different parts of the island. But all traced their maternal ancestry back to the Isle of Rona.
Drive to the north end of Skye past the eroded cliffs and pinnacles of Trotternish, high above the sea, and Rona is the low rocky island on your right, lying 5 miles offshore. It looks as if it is connected to the longer, higher island of Raasay to the south, but it is not. A hidden sea channel separates the two islands. Rona is deserted now, but once held a few crofting families who fished in the dark blue seas. Their houses have been abandoned and only the lighthouse, white against the rocks, is visible from Skye.
What must have happened on Rona to account for the unusual DNA I had found on Skye was a mutation, a slight change in the DNA of one of the ancestors. Silent, unnoticed and with no effect at all on the woman in whom this event had occurred, just one DNA base, one bead on the chain, had changed. The new sequence was unique, never seen before in the history of the world. If this woman had been childless or had only sons, it would have died with her. No one would ever know it had been created. But she must have had children, and at least one of her children must have been a girl for her mDNA to be passed on. Through this girl, or her descendants, this new sequence left the island of Rona and found a home on nearby Skye, where it still remains. From there, perhaps one of the daughters in the next generation went to live on Lewis while another travelled down to Glasgow. I cannot tell exactly when this happened, but the journeys have been recorded by the genes of the descendants. I have not found this particular sequence of DNA letters anywhere else. Nor has anyone as far as I am aware. That doesn’t mean it isn’t there in other parts of Scotland, or Ireland, or Wales, or England. Just that we haven’t found it. That is always the way, and always will be. We will never know everything there is to know about this new gene and what happened to it. We can only piece together something of its journey from the scraps of information that have both survived to the present day and that we have found in the cells of people we have tested.
This is a little story of one particular gene, a new version that has changed very slightly. If we ever do come across it again in the future, we will know it has travelled from Rona. It is a fragment, like a piece of pottery or a flint tool, and just as reliant on the twin necessities of survival and discovery as any archaeological remains. This is how I would build the genetic history of the Isles, by sifting through the thousands of fragments, trying to make sense of them. I would treat them as if they were the scattered shards of broken pottery and do what I could to understand what they meant. This was the point at which I decided to become a genetic archaeologist. I would work with fragments of DNA, perfectly preserved in the bodies of descendants, to reconstruct the travels of their ancestors with the same discipline that an archaeologist would use when excavating a site. Collect, examine, record, compare, interpret. In my mind’s eye, even though they were in reality stored on my computer, I began to think of them as, literally, a pile of fragments, pottery perhaps or maybe coins. Yes, coins would be an even better metaphor. Through Chris Howgego, a friend and colleague from Oxford, I had been allowed to examine the Ashmolean Museum’s collection of ancient gold coins from Britain. Many are over 2,000 years old but still fresh and lustrous, stamped with the image of an ancient tribal king or the stylized outline of a horse, a chariot wheel or an ear of wheat. I would set out to use the genes to interpret the past, just as Chris Howgego used his coins.
Of course they would tell very different stories. Coins and genes are not the same, but neither are they so very different. Both have to obey the rules of survival and discovery and, in the case of gold coins at least, both had been preserved virtually intact. Both bore inscriptions, either the name of a king or the sequence of a piece of DNA. A coin from a distant land discovered in Britain is a witness to a journey made, just as much as a fragment of mDNA must have made its way to the Isles at some time in the past in the cells of an ancestor. Coins have one thing that is conspicuously lacking in DNA and that is a date. Though the Iron Age coins in the Ashmolean Museum do not have a calendar date impressed on them, their date of manufacture can be worked out from the tribal chief whose image or inscription is on the coin. For example, several are inscribed with the letters CVNO, denoting that they were minted during the reign of Cunobelinus, King of the Catuvellauni some time between 60 and 41 BC.
With DNA we are not quite so fortunate. It does not bear a date stamp, but there is information on time depth to be had along the same lines that we have already used
when working out how long ago the clan mothers lived. We can get an idea, though only an approximate one, of how long a group of mDNA or Y-chromosome ‘gene-coins’ has been in a location by seeing how they differ from one another. But it can be tricky, as we will find out.