and the Y chromosome, inherited by men from their fathers, and makes the following claims: The genetic makeup of Britain and Ireland is overwhelmingly what it has been since the Neolithic period and to a very considerable extent since the Mesolithic period, especially in the female line, i.e. those people, who in time would become identified as British Celts (culturally speaking), but who (genetically speaking) should more properly be called Cro-Magnon. In continental Europe, this same Cro-Magnon genetic legacy gave rise to the Basques. "Basque" and "Celt" are cultural designations, not genetic ones. The contribution of the Celts of Central Europe to the genetic makeup of Britain and Ireland was minimal; most of the genetic contribution to the British Isles of those we think of as Celtic, came from western continental Europe, i.e. the Atlantic seaboard. The Picts were not a separate people: the genetic makeup of the formerly Pictish areas of Scotland shows no significant differences from the general profile of the rest of Britain. The two "Pictland" regions are Tayside and Grampian. The Anglo-Saxons are supposed, by some, to have made a substantial contribution to the genetic makeup of England, but in Sykes's opinion it was under 20 percent of the total, even in Southern England. The Vikings (Danes and Norwegians) also made a substantial contribution, which is concentrated in central, northern and eastern England – the territories of the ancient Danelaw. There is a very heavy Viking contribution in the Orkney and Shetland Islands, in the vicinity of 40 percent. Women as well as men contributed substantially in all these areas, showing that the Vikings engaged in large-scale settlement. The Norman contribution was extremely small, on the order of 2 percent. There are only sparse traces of the Roman occupation, almost all in Southern England. In spite of all these later contributions, the genetic makeup of the British Isles remains overwhelmingly what it was in the Neolithic: a mixture of the first Mesolithic inhabitants with Neolithic settlers who came by sea from Iberia and ultimately from the eastern Mediterranean. There is a difference between the genetic histories of men and women in Britain and Ireland. The matrilineages show a mixture of original Mesolithic inhabitants and later Neolithic arrivals from Iberia, whereas the patrilineages are much more strongly correlated with Iberia. There is evidence for a "Genghis Khan effect", whereby some male lineages in ancient times were much