Race in Tolkien is Reality Rather Than Socially Constructed

In Middle Earth, unlike reality, race is objectively real rather than socially constructed. There are species (elves, men, dwarves, etc.), but within those species there are races that conform to 19th-century race theory, in that their physical attributes (hair color, etc.) are associated with non-physical attributes that are both personal and cultural. There is also an explicit racial hierarchy which is, again, real in the world of the story. Middle Earth is literally a racist’s fantasy land.

It’s also structured by colonialist assumptions: Gondor is an imperial power. It gave the Dunlendings’ land to the Rohirrim, for example, and that is constructed as having been right and unproblematic. There is also the fairly obvious point that all the “good” species and races are constructed through references to European cultures (especially northwestern Europe), and the “bad” races are constructed through orientalist stereotypes. Mostly those constructions are based on medieval tropes—Saracen armies, etc.

There’s also a very strong influence of 19th-century Anglo-Saxonism, which was a profoundly racist ideology used to justify British imperialism and American expansionism.