In the days before fast long-distance travel, the more chauvenistic people supported race war, to make more space for one's own gene pool and cultural pool. The stronger dominated the weaker, killed, took slaves, used them in any way they saw fit. (But also, in any cultural contact, some of the genes and values of the weaker get integrated into the culture of the stronger.) This is "the law of the jungle" (some might say the law of natural evolution), usually obeyed by instinct rather than intent, by all viable primitive societies that have no all-inclusive community or government. It continues even into modern times as long as we don't have a world government. To the degree that we have integrated (by force or otherwise) cultures or communities, we must necessarily learn to live peacefully with our neighbors.
It seems the human race began in cental Africa, and evolved a certain level of culture there. Some adventurous people traveled to North Africa and developed a more advanced, but later, culture. This pattern continued into Europe, maybe Asia and would have in the Americas. Limited and local cross-fertilization improved all cultures. Without new factors it seems that, given time, the South Americans eventually would have developed the most advanced culture of all, because they (or most of them) traveled further, and necessarily evolved further. The principle of "the rich get richer" means that the more advanced are usually also the more rapidly evolving.
But since the world is finite and spherical, this could not continue. Europeans developed long distance sea travel, disrupting the pattern, creating more frequent interactions between distant strains of humanity. African cultures had never developed enough to hold their own. "American" cultures hadn't had the time they needed to develop. Though they may have had more potential, they had put their energy into expansion for a longer time, so the Europeans had more advanced cultures. Asian cultures, having settled down earlier, were a little more developed, and now appear to be coming out on top. They also had a little more warning of the change than the "Americans".
Was the white race stronger than the black race only in aggressive, oppressive powers? Was the black race more advanced in more spiritual pursuits? I'd have to see some good evidence of that. I think the two usually go together. Ultimately, in natural evolution, being able to survive and prosper among competitors and preditors is the most important evolutionary trait.
We like to think we're evolving away from the law of the jungle, but in some ways, we're going in the other direction. The debt we owe to evolution, along with a lot of others, is coming due. I see value both in diversity and in selective evolution. But human natural selection has been almost completely phased out as we've built hospitals and developed social programs around the world. Some of these programs cause backward evolution when they encourage more reproduction among the incapable than among the capable. We may eventually reach a time of planned evolution, when we can agree on what traits are beneficial and which are a burden to joint human goals. At the same time, we should support some random diversity.