It's really weird how the idea of "whiteness" has changed and morphed over time, as well as based on circumstances even in the same time.


For example, the Irish were considered a different "race" at one point.


Another more recent - and hilarious - example was the case of neo-Nazis getting DNA tests to find out how "pure" they were, and the reactions and coping mechanisms that followed when it turns out they weren't 100% "white".

http://www.pbs.org/newshour/updates/white-supremacists-respond-genetics-say-theyre-not-white/