I think there will never be something as a unique mixed race. It is not possible, due to humans nature. Immigration, on the other hand, always existed and is unavoidable. Remember well how Celtic people invaded Italy and helped to create new Roman Empire. Remember how barbarian tribes invaded the Roman Empire but re§built it to the Empire of Franks (or Holy Roman Empire).
And, look at the USA - there is a strong intermixture of Caucasian population, one person having the ancestry of many european nations... But this scheme is possible only in the environment of migrating other continent with low resistance of domestic population. In Europe, there will be strong ethnic groups and rising mixture of different races, but never till higher level as it has been in history. Because we are living in this time, we are thinking of our changes and tremendous vast changes of European population in the past seems for as as something normal - or we have completely forgotten them.
By the way - we Caucasians, are so worried of intermixing with others in Europe, but nobody of us is taking into account that we have brought our genes into Africa, all Latin America, Australia... and for example some Algerians or Angolans are raised on OUR EUROPEAN culture for decades (because of our past collonial and, rassistic era), have intermixed with us, their culture is our... and when those people are coming to Lisbon or London or Paris, we are becaming worying of immigrants... What a nice picture, a distinguished citizen of old Rome would not believe that
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