This is due to furthur historical demographic change. In England between the 1700's up till the 1960's millions of people left for the new world and were replaced by welsh, irish and scottish immigrants, which the act of union and the industrial revolution gave impetus too. I mention this because I do see history on the whole as being factual. When conducting genetic testing for historical purposes, it must take into account demographic movements, genealogy and history so as to rule out incorrect results and interpretations. In ireland they only sample people with gaelic irish surnames, yet in england they include people with irish, scottish and welsh surnames. Hopefully in the future, all y-dna tests will be based on people with english surnames and a proven paper trail from the 1700's. The people of the isles project due this year, includes english samples with celtic surnames, which for me does not give a fair result. Though I talk only of england, I imagine the same holds true for other populations, such as the french, dutch, germans etc.I apologise if the text is too long.