1 - I know that, but the images in question had SS symbols on helmets;
2 - I know that too, and it's likely to have happened once or twice or a dozen times, but I think no genetic or archeological trace of something like this definitely happening has yet been found;
3 - now here I think I've read about some genetic traces found even;
... and, second, it's more about something being normal as your first association.
Say, when you think of a universally gifted person, Dolph Lundgren won't quite fit your stereotype.