I don't like the term "bi-racial" or "mixed" either, all of humanity is mixed; the term is superfluous. In fact I like biracial even less because it implies a mixing of characteristics that are arbitrary and randomly inherited.
This is why one sibling can come out looking 100% Black (using your terminology), and another can come out looking 100% white--but they are both bi-racial?!
The people I was thinking about who are very dark but have straight hair live in southern India, as well as other parts of the world.
I assume you would put this young lady in the "Black" category, since she has naturally straight hair. I would then have to presume kinky hair is not a requirement for being Black.
Of course, I could provide additional examples of humans without broad noses, thick lips, and or even dark skin, that you would probably call Black, or not, depending on your arbitrary definition.
But I doubt any of this will have any impact on your belief in race, you as well as most people since to want to rigidly adhere to the belief in race.
@Cynique, has anyone ever asked you "What are you?" As in what is your race. The question may sound pretty innocuous, but what they are really trying to determine is what "race" you are, so that they can associate all of the characteristics of that race too you. It is a lot easier than actually getting to know you.
Over time I hope humanity will come to embrace reality, and dispense with archaic racial categories, and the resulting prejudice and bigotry that accompanies it.
Perhaps without racism as a distraction, we can deal with our real enemy.