[LocoColt04]

You know, that's not a bad theory, actually. The idea that we are subconsciously choosing mates of other ethnicities based on the idea of natural evolution is a pretty good thought to mull over. I certainly think it is possible that we, as a human race, are looking to strengthen our various ethnicities by mixing our blood with that of other, more diverse cultures.

While some people may be doing it consciously, I think your teacher's assumption that it's a subconscious thought process may not be far off from the truth.