Um... have you looked around? We are already -- all of us -- mixed.

There is no such thing as a pure anything. And we've been mixed forever. In a 1000 years, the race line will still be there unless white people give up the idea of being special because they are white... and then we will all be varying shades of brown -- just like African-Americans are right now.

(The gene pool, I think, was never meant to be segregated.)