I'd say they were cultural minorities, not ethnic. There's no way someone's forefathers married people of the same race for over 2000 years, unless they live on Christmas Island (or The Ilse of Sheppey).
In Europe, especially Western Europe, it would be largely impossible because of the great migrations, Roman colonisation, Vikings, Saxons, Goths, Vandals etc etc. Then look at the massive population increase from across Europe with countries of a few hundred thousand in 1700 to millions by the 1900s and the steady movement from country to town. They'd hardly remain with the same people let alone 'racial group'. Not to mention most people can only trace their family tree back a few generations anyway, once you're off the Church records you could be related to anyone.
I'm Count Bohemond of Taranto's great, great, great x 12 grandson by the way.
EoR