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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 readouts
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.