Utopia doesn't exist. It's impossible.

The world is large enough that even if we were all interbred according to a very detailed regimen in order to evenly mix and distribute the genepool, there would STILL be a variance of cultures, and in time, "races". After all, race isn't just skin color.

I can't imagine anything or anyone derived from human-kind in the near future capable of forcing a homogeneous culture upon the whole population, either.

Maybe when the singularity comes along though Or the aliens.