Blood of the Isles (14 page)

I realized at once that these clan mothers, as I called them, were not some kind of theoretical ancestors, but real living, breathing women. No, not just women, they were mothers as well. Mothers who had survived and whose children, or at least whose daughters, had survived and who in turn had survived and had daughters and so on, right down to the present day. Though men have mDNA, they do not pass it on to their children, but they do inherit it from their mothers. Originally to emphasize to myself that these clan mothers were real individuals, I gave them names, each of which began with the letter by which the seven different groups were by then known among scientists. So the clan mother of Group H became Helena, T became Tara, J became Jasmine, X became Xenia, V became Velda, K became Katrine and U became Ursula. Over 95 per cent of native Europeans are in one of the seven maternal clans, and so it followed that these seven women were the maternal ancestors of almost all Europeans. As
soon as I had given them names, they came alive and I had to know more about them. I became quite desperate to build up a picture of their lives. I wanted to know all there was to know about these seven women, the women who soon came to be known as the Seven Daughters of Eve.

The first thing I wanted to know was how long ago these seven women had lived. Were we talking about hundreds, or thousands, or tens of thousands of years ago? The answer came by looking at the extra mutations within the clan. Taking the clan defined by the signature mutations at 126 and 294, which is the clan of Tara and the one to which I belong, everyone within the clan shares these two mutations, for the simple reason that Tara herself had these mutations and everyone in the clan is one of her direct matrilineal descendants. These two mutations have come down through the generations unchanged from the clan mother herself. But how many generations? How long ago did Tara live? That is where the additional mutations come in. Although roughly a third of people in Tara’s clan have only these two mutations, the rest have additional changes. I have one extra mutation, at position 292, which makes my mDNA sequence 126, 292, 294. Other members of the clan have experienced more mutations. All these additional mutations
must
have occurred since Tara’s time. Fortunately we know the mutation rate for the mDNA control region. It is approximately one change every 20,000 years. Since mutations happen completely randomly, not every line of descent from Tara will experience the same number of mutations. Some may be spared altogether and retain just the signature mutations at 126 and 294. Some
maternal lines, like mine, will have been hit once since Tara’s time, others more than once, some not at all. By working out the
average
number of additional mutations within the clan, we can then estimate how old the clan is, or, to put it another way, how long ago Tara herself lived. For her clan, the average number of additional mutations within the clan is almost exactly 0.85. With a mutation rate of 1 change per 20,000 years, the conclusion is that Tara lived 17,000 years ago.

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.

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.

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.