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esponsible for the unusual genetics of the Hebrides. And both of these branches, the
Mediterranean Jasmines and the younger Tarans, had a distinctly seaborne flavour about them. They
are spread all along the Atlantic fringe, but rarely inland. This was a definite clue, but the solution
was not yet clearly visible. The Hebrides are also unusual in having a very high concentration of
members of the Katrine clan, especially on Lewis, where they reach the highest frequency of
anywhere in Scotland.
It was during my research on Skye that I stumbled across a genetic phenomenon which, with
hindsight, I should have investigated much sooner. At that stage I had already discovered the link
between my own surname and a particular Y-chromosome profile. Foolishly imagining that such a
link to a common founder would only be found in comparatively uncommon English surnames, it
took another year before I realized the same might be true, albeit in diluted form, among Scottish
clans as well. My research student Jayne Nicholson and I found a rare Y-chromosome profile in
our Skye samples and, when we compared it to others collected at donor sessions elsewhere in
Scotland, we noticed that we found it almost exclusively among men with the surnames Macdonald,
McDougall and Macalister. It was Jayne who remarked that all three names were said to be
descended, according to traditional clan genealogies, from Somerled, the Celtic hero whom we
have already encountered. It was Somerled who was responsible for ending the power of the
Norse earls of Orkney in Argyll and the Hebrides, and who died at Renfrew during his ill-fated
invasion of Scotland in 1164. Jayne set about writing to men with these three names asking for
DNA samples, while I contacted the five living clan chiefs whose genealogies traced back to
Somerled. They all agreed to help and, I’m very glad to report, all five had inherited the same Y-
chromosome that we had seen in the men with the three surnames. Somerled’s Y-chromosome had
done extremely well and, thanks to its association with a powerful and wealthy clan, has become
very common indeed in the Highlands and Islands, and among Highlanders who have emigrated
overseas. Roughly a quarter of Macdonalds, a third of McDougalls and 40 per cent of Macalisters
are direct paternal descendants of Somerled. This is not just true in Scotland, but throughout the
world; it has been estimated that there are 200,000 men who carry Somerled’s Y-chromosome as
proof of their descent from the man who drove the Norse from the Isles.
I am only summarizing here what was an exhilarating search for the legacy of this illustrious
Celtic hero because I have written about it at length in Adam’s Curse. Soon after this discovery –
which was also paralleled by the Macleods of Skye, though there the linkage was to a different
chromosome – I heard about the research on Genghis Khan’s profligate genetic legacy. His Y-
chromosome, passed down through generations of emperor sons, is now found in an estimated 16
million male descendants. This might put Somerled’s 200,000 descendants in the shade, but the
feeling has grown among geneticists that the Genghis effect could be an important factor in the rise
and fall of Y-chromosomes, not only in Asia but in other parts of the world, including the Isles.
Recently Brian McEvoy and Dan Bradley from Dublin have found an Irish equivalent to the
Macdonalds and the Macleods. Again starting with an unusual Y-chromosome, they noticed its
occurrence in a related set of surnames that were linked to branches of the Ui Neill, the clan that
had held the High Kingship at Tara, and had expelled the Dál Riata to Argyll. The Ui Neill
equivalent of Somerled was Niall Noigiallach, better known as Niall of the Nine Hostages, who
lived in the second half of the fourth century AD. This was a time when the Romans were beginning
to withdraw from mainland Britain. According to legend, Niall raided and harassed western