I've ran my genetic data through multiple filters, and depending on how far back I go, at 500 years I am ~99.7% European, mainly the North West area, with the rest Native American and possibly Ashkenazi. My ancient DNA accurately shows I'm Indo-Aryan, extending into Europe, Siberia, East Asia Americas. I do not have any sub-Saharan African. And, DNA testing is somewhat inaccurate, which is why I've ran the data through probably 30 filters or so, to get an idea. But anyways, I'm aware of my history, and I understand it has been largely gradual... and even if some parts were not, such as maybe the mixing with Neanderthal- of which I'm ~2.4%, I find my heritage worth fighting for.
Though it is a big "duh" that it is not so Black and White or that we have neat little dividers, there is a way with 90% certainty at least to find a person's geographical place of origin, assuming they are where they are native to. Skull forms are different. Bone structure is different. Teeth are different. Though 'race' (as a word in attempt to categorize, place, keep in order) may not be so clearly defined, and the sociocultural may have played a role, you are basically stating some hopeful leftist egalitarian commie yada as fact, and ignoring that there is actually true diversity in the world. If you notice, I rarely use the word 'race' without some kind of extra attention to it- hesitation with it. I prefer "populations". And some populations can blend more or less seamlessly with others, and gracefully, naturally. When the dark skinned Blacks pour into Europe in droves, and others, and if you expect them to be treated as part of the clan and mated with, as your agenda pushes ("we are all the same/it's a sociological construct and that's the end of it racist!!!"), denying reality, Europe will soon lose its heritage- it's own unique diversity- by combination of less births of natives than invaders/migrants, and intermixing with migrants. I'm definitely not hot on that idea, the people I largely came from being represented in such a small amount after time, in the birth of them, into relative obscurity, because of 'altruism'.
You are destructive.
When China does it to Tibet, it is Genocide, and they are like Greeks to the typical image of "Chinese" that people get, to put a general category (no need to nit pick, I know...), as Greeks are to Danes, with a margin of inaccuracy accepted. The only thing missing is a clear indication of who is attempting to commit genocide. Let's say that's you.
A 'White' girl does not sprout up in sub-Saharan Africa, naturally, from Black parents. A Chinese couple will not give birth to a West European child. Please, don't marry a White girl, as if you would even recognize one.
Finally, as I've stated before, there is plenty enough variation in European populations, that there is no known imperative to mix with sub-Saharan Africans. It may in fact weaken them. And at any rate, it is destructive the the uniqueness of the European peoples.