All I know is that my ancestors came from Wales, Scotland, England, N Ireland, Ireland, and Germany. But I do have a very distant Italian Ancestor who fought with William when he invaded England.
But in each case for DNA purposes, before they arrived in those places (cultures, locations, nations) they had traveled from somewhere else, in many/most cases. (example the Welsh likely came across from Brittany-hence the shared languages of "Breton" and "Welsh.")
Taking Britain, there were some earliest "indigenous" people of Britain (pre-Celts?). Then came Celts, Romans, Angles, Saxons, Jutes, Frisians, Belgians, Norse, others etc.
Or take southern Italy for another case. Etruscans, Greeks, Romans, Normans, muslims, Spaniards, etc. Likewise Spain.
But even predating those migrations, the first people advanced then retreated with changes in climate, e.g. Ice Age.
I still have the open question of when in migratory history, these father-mother Haplogroups were established?
They dug up a lot of bodies in Britain, of people descended from Norse, and one company (livingdna.com) calls them UK, and another (ancestry.com) calls them Scandinavian.
The site gedmatch.com offers several additional algorithms to classfy DNA with different labels, like "Atlantic," "Baltic," and "Mediterranean" etc. for instance.
Finally DNA science is advancing rapidly. They are using stem cells now, to treat cancer. There are large scientific firms, dedicated to medicine, not genealogy as a hobby for where Grandpa Eric's family came from?
