The Scotsman web site and newspaper has published a fascinating article by Alistair Moffat and Dr Jim Wilson about the DNA of Scotland. As might be expected by anyone who has studied Scotland's ancient history, most of Scotland's males carry Y-chromosome DNA from the Vikings.
The Viking attacks began in AD793 with the surprise assault on the Holy Island of Lindisfarne. Later waves of Viking invaders landed in northern, western, and southern Scotland as well as some in what is now Ireland. Clan names often show high percentages of males sharing the same DNA. Clan MacLeod is an especially interesting case study. From a sample of the DNA of 45 Macleod Y chromosomes almost half, 47 per cent, clearly show social selection at work in that they descend from one individual.
You can read a lot more about the history of Scotland being verified by DNA in the Scotsman at http://thescotsman.scotsman.com/features/Scotland39s-DNA-Who-do-you.6727434.jp