This is from the first page of Tolkien’s The Fellowship of the Ring. It is the first time he uses the word “race” in the book (though he did use it in The Hobbit as well). Considering Tolkien’s place as the godfather of the fantasy genre, it’s unsurprising that his conception of the “races” of Middle Earth have become more-or-less standard across the fantasy genre.
But Tolkien’s conception of “race” is a huge problem. His ideas have been bred into the core of the fantasy genre—not just literature, but films and games too. Contemporary authors have had to work hard to free the genre from this original sin.
The core of the problem is that Tolkien conflates race, culture, and ability. Hobbits, he says, are a race, and based upon a combination their hereditary traits and cultural practices, are better at being stealthy than other races.
Tolkien does this throughout his novels, outlining the “racial” characteristics of men, of dwarves, of elves, of orcs, and those few of mixed ancestry (like Aragorn or the Uruk-Hai). As Helen Young, author of Race and Popular Fantasy Literature put it in a recent interview with the Pacific Standard: "In Middle Earth, unlike reality, race is objectively real rather than socially constructed.".