You know why, politics. It’s insanely obvious too, it’s easy now to convince people because we are used to being around each other a white person is used to an Africans features, mannerisms etc and we now often share the same/similar culture, so when big brained “scientists” say “one race human race!” People are like ya sure seems reasonable I guess. But if you want the truth look to the first people that encountered other races, they immediately recognized them to be a different thing, different sub species at least, some weren’t even sure they were humans at first. Look at it this way, let’s say we go to space, and meet aliens, we are like oh shit it’s aliens! Obviously, they look totally different they talk with their ears, whatever. Now imagine 100 years later and “scientists” are like , actually we looked into it and it turns out these aliens are actually just normal humans after all! And people are like, oh snap your right, not sure why I never noticed it before but that one alien looks identical to my brother Dave lol, why did we think they were aliens? It was just humans from an earlier ship or some shit woops. Rediculous right? Because if we went to space and saw other humans our first thought would be, “oh shit did we find other humans out here? That’s amazing!” And we would investigate immediately obviously. Similarly, if early explorers met say Africans, and they were the same species/subspecies, it would be immediately obvious to them, they are around other humans all day after all. Or at least, their first instinct wouldn’t be, these are something else. Even if you got 1 or 2 early explorers that were retards/overly in group minded or something, it wouldn’t be all of them. We like to dismiss it as every person not in current year was just a dumb racist retard, but they were basically just as smart as us, with less advanced tech, and humans are very good at picking out other humans.