Though nation-state is the basis of organisation of the current human society on a larger plain, even a cursory look at the current demographic map of the world suggests that no society is ethnically pure.
Travel is now faster and easier.
Media and communication technology has vastly reduced the pain of physical distance. Economy too is getting globalised. All these have encouraged families and societies to split and spread and yet retain essential bonds and emotional links. Media enables even smaller ethnic minorities to survive with distinct cultural identity. All these have weakened the aggressive nature of nationalism.