Science Fiction & Fantasy Stack Exchange is a question and answer site for science fiction and fantasy enthusiasts. It only takes a minute to sign up.
Sign up to join this community
One thing that separates Firefly from many other works of science fiction set in space is that there are no aliens. All sentient beings either are or used to be human.
However, I very much doubt Firefly was the first work to do this.
What was the first work set in space that featured multiple civilizations but no aliens?
A potential early candidate is the 1886 story Man Abroad. A Yarn of Some Other Century. (see here for availability of used copies) The entry for this book in Bleiler's Science Fiction: The Early Years indicates human colonization of much of the solar system, but no mention of sentient aliens (though there may be alien vegetation). Here's the start of the summary:
The time is not specified, but is far enough away for man to have colonized the whole solar system. The other planets and the asteroids are like Earth, with similar atmospheres and gravity, and presumably comparable vegetation. At some time the past a comet grazed earth, carrying away a group of scientists and depositing them on the moon, where they survived quite well. This led to a space land-rush, and in a very short time electric airships riding the interplanetary electric currents made their way through the solar system. At present the major planets are independent nations (there is an element of satire here on nineteenth-century foreign affairs), with Mercury, Venus, and Mars kingdoms, and Jupiter an empire. All are on touchy diplomatic relations with one anohter, and war is perpetually likely. Most of the asteroids are sitll unclaimed by the major nations. Some are unsettled; others are privately owned by wealthy persons. All these worlds seem to be economically viable, but Mercury is favored with enormous gold deposits. The economic system throughout the solar system (exception to be noted) is laissez faire capitalism, and greed dominates everything.
The summary goes on to discuss the plot, involving an outbreak of war and a journalist who discovers an asteroid that has been settled by followers of Henry George who have created a type of socialist economy there, which is superior to laissez faire capitalism and eventually spreads to other worlds. The summary concludes with
The author's chief interest is political, and the science-fictional aspects are usually a matter of a line or two of background. The story is filled with nineteenth-century topical references, most of which would mean little except to a historical specialist. An annotated edition would be desirable.
Since Rogue Jedi approved this answer after I added this book, I'm editing out the other stories I had here earlier, but you can check out the edit history on this answer if you want to see some other pre-Foundation examples that might fit from the 1920s through the early 1940s.
I don't know if he was the first, but Isaac Asimov's Foundation stories (the first one was written in 1941 and published in 1942) feature a galactic empire with many worlds, but without aliens.
Asimov explained the reason for that in an essay:
[John Campbell, editor of Astounding magazine] did not like to see Earthmen lose out to aliens, or to have Earthmen pictured as in any way inferior. Even if Earthmen were behind technologically, they should win anyway because they invariably were smarter, or braver, or had a superior sense of humor, or something.
I, however, [...] felt that Earthmen [...] might well prove inferior in many vital ways to other civilized races; that Earthmen might lose out to the aliens; that they might even deserve to lose out. [...]
I wrote a sequel to “Homo Sol,” which I called “The Imaginary,” in which I evaded the issue by having Earthmen not appear (and Campbell rejected it). [...] I continued to want to write “superscience stories” my way, however, and continued to probe for strategies that would allow me to do so without encountering Campbellian resistance.
I arrived at the answer when I first thought of my story “Foundation.” For it, I needed a Galactic Empire, as in “Homo Sol,” and I wanted a free hand to have it develop as I wished. The answer, when it came to me, was so simple, I can only wonder why it took me so long to reach it. Instead of having an Empire with no human beings as in “The Imaginary,” I would have an Empire with nothing but human beings. I would not even have robots in it.
Thus was born the “all-human Galaxy.”
—The All-Human Galaxy, 1983
Asimov seems to have preferred humans over aliens; his Galactic Empire series features humans (and occasionally robots), but no BEMs. While written well after Foundation, his The Stars, Like Dust occurs much earlier in-universe, preceding the establishment of the Trantorian Empire. It features a smaller empire, the Tyrannian Empire, a rebellion against it, and the search for a secret weapon that has been hidden (or perhaps simply abandoned) on Earth.
Unless I'm failing to recall correctly (and this answer from Quora seems to back it up), all civilization's in Dune (1965) were descendant from humans. Paul's quote about becoming a hitler also ties this in to being a far-future scifi based on present day earth. It is mentioned that the Imperium hasn't yet ruled out the possibility of aliens (as they keep atomics stockpiled in the event of finding a malevolent civilization), but thus far has not.
Murray Leinster also seems to have favoured all-human universes. Both Operation Outer Space and The Last Space Ship assume this iirc.
