The World of Greyhawk (1983) is another example of concepts from late 19th and early 20th century race theory making their way into D&D. Even reading it as a youth I found its obsession with race to be weird.
“For two centuries the Oerid and Suel battled each other and the fragmenting humanoid hordes for possession of the central area of the Flanaess, incidentally engaging the Flannish and demi-humans. In a few places the two racial stocks intermixed – notably the Sheldomar Valley where, except for the Hold of the Sea Princes, the peoples of the Kingdom of Keoland, Gran March, the Ulek States and nearby petty lands are mixed Oerid-Suel stock.”
“People of the Duchy of Tenh are pure Flan, proud of their bronze color. Geoff and Sterich, despite mixture, show strong Flan racial influence. The Rovers of the Barrens are of the copper-toned sort of Flannae, although the western tribes show the golden skin color of the Baklunish due to interbreeding with the Wolf Nomad tribes. The people of the Hold of Stone Fist and the citizens of the Theocracy of the Pale are primarily hybrids, the former Flan/Suel, the latter Flan/Oeridian. The inhabitants of the Pale are particularly handsome.”
There’s literally over a page and a half more of this in exactly the same vein.
I’m pretty sure Gary was riffing off of Robert E Howard’s essay The Hyborian Age (1936), replicating its language and some of its ideas.
"Only in the province of Gunderland, where the people keep no slaves, is the pure Hyborian stock found unblemished. But the barbarians have kept their bloodstream pure; the Cimmerians are tall and powerful, with dark hair and blue or grey eyes."
“The Stygians are tall and well made, dusky, straight-featured - at least the ruling classes are of that type. The lower classes are a down-trodden mongrel horde, a mixture of negroid, Stygian, Shemitish, even Hyborian bloods.”
Compare with Lothrop Stoddard’s The Rising Tide of Color Against White Supremacy (1920)
“The heroes of the revolution—Bolívar, Miranda, San Martín, and the rest—were aristocrats of pure-white blood."
“Analyses of these hybrid stocks show remarkable similarities to the mongrel chaos of the declining Roman Empire.”
“To be sure, where members of the same race-stock intermarry (as English and Swedish Nordics, or French and British Mediterraneans), there seems to be genuine amalgamation. In most other cases, however, the result is not a blend but a mechanical mixture.”