
I regret that both authors have resorted to nicknames for the various mtDNA and Y-chromosome haplogroups at the base of their vast research. For example, my personal DNA testing has placed me in a precise paternal haplogroup designated as R1b1b2a1b5. For Oppenheimer, on the other hand, I'm a member of the Ruisko tribe, which Sykes prefers to label the Oisin tribe. For serious adepts of DNA testing, the official haplogroup terminology is both necessary and sufficient, and the silly nicknames introduced by Oppenheimer and Sykes serve no useful purpose.
The existence of interesting in-depth studies such as those of Oppenheimer and Sykes evokes a common criticism that is often raised by people who are wary of the validity of all kinds of genealogical research, be it strictly personal (as when I explain with pride that my Skyvington patriarch in England came over with William the Conqueror, or that I've established another ancestral line running back up to this same Norman invader) or applied to the peoples of vast regions such as the British Isles. To get the gist of this criticism, look at the following pedigree chart (so-called because all the T-shaped signs can be imagined as goose tracks), in which my paternal ancestors are designated by blue dots, and my maternal ancestors by pink dots:

Getting back to the kind of research conducted by Oppenheimer and Sykes, isn't it a huge weakness to draw conclusions based merely upon the Y-chromosome and mtDNA profiles of present-day residents of the British Isles? If they had tested, say, a (fictive) London chap named George Skyvington and found that he (like me) was a descendant of the Ruisko/Oisin tribe, wouldn't they be drawing hasty and unsound conclusions by ignoring, as it were, that George might have had lots of other ancestors from quite remote tribes: Eskimos, American Red Indians, Chinese, Pacific Islanders, Tasmanian Aborigines, etc? Doesn't the absence of such perfectly-real ancestors cast a dark cloud of incompleteness or imperfection upon the global outcome of the research carried out by Oppenheimer and Sykes?
No, not at all. Don't forget that these researchers have been performing DNA tests upon large groups of people living in the British Isles. Consequently, if indeed our George Skyvington had ancestors belonging to "tribes" such as Eskimos, American Red Indians, etc, then it's possible that the existence of these ancestors will show up in the Y-chromosome and mtDNA data obtained from some of George's "genetic cousins"… about whom he probably knows nothing (and never will). Statistically, if the tested population is large enough (a criterion that can be determined mathematically), everything should come out in the wash, as it were. George's Eskimo and Red Indian ancestors won't be totally forgotten. They'll merely be associated with other tested individuals. And George won't even be tempted to complain about "his" ancestors being associated with total strangers, because he simply won't know that this has happened. Maybe George might even look at research results and say to himself: "My God, to think that, here in my native England, I'm living alongside descendants of Eskimos, American Red Indians, Chinese, Pacific Islanders, Tasmanian Aborigines, etc!"