Edgar Rice Burroughs, for instance. Different tribes of blacks would have their physical differences enumerated with care. If you know your turn-of-the-century racial theories, it's not difficult to decipher this:
The Abyssinians themselves are a fine looking race of black men—tall, muscular, with fine teeth, and regular features, which incline distinctly toward Semitic mold—I refer to the full-blooded natives of Abyssinia. They are the patricians—the aristocracy. The army is officered almost exclusively by them. Among the soldiery a lower type of negro predominates, with thicker lips and broader, flatter noses.
even though he has them consider whites to be an inferior sort of being, many of them slaves, and living in the poor quarters when free.
Even writers not moved to use those distinctions as a kind of short-hand for character would nevertheless deploy them to describe. In one Time Patrol story, Poul Anderson's characters know that history has changed, because in all the millennia they cover, New York City never was occupied by a mix of brachycephalic whites and American Indians, using steam-powered cars. He also used it to indicate new and different humans; "Time Lag" has a planet inhabited by a race of blue-eyed blonds -- with slanted eyes.
To be sure, reading the straight stuff gets some details that never make it into the fiction, where you can have unquestionably superior and inferior races and set up history accordingly. It can be interesting to watch the attempts to depict one's race as superior in defiance of historical fact. Italy would point to the grandeur that was Rome, but there was no denying it had gone down in the world since then. Teutonicists had the opposite problem; much as they might claim that the patrician class in Rome was actually Germanic invaders -- as were the Greek aristocrats -- and those countries had declined when they stopped maintaining their racial purity, and well as Germany was doing in the modern world, there was no denying that the Germans in classical times had hardly been impressive. English Teutonicists, wishing to give their own country priority, would claim that the pure Nordic breed was all but wiped out in the Thirty Years' War, leaving its superiority to England alone. (American ones often claimed that there had been some remnants after the war, but they had all emigrated, to America.)
Robert E. Howard had his three races, of blonds, red-heads, and black-haired men, a distinction thought eminently important in the era.
And that, mind you, is in the 20th century. Pushing the matter back farther brings even stranger things to the racial questions. Yet the characters of a work of fiction seldom slice up the human race into divisions much different than modern day ones.