Morrison, William – “The Inner Worlds” (1954)
Finally, something inventive and alien. Cold opens with characters conversing while travelling around in some sort of muddy channels and rivers, one of whom tells another that non-endo invaders, smaller than their worlds, have invaded from outer space. One character, Raldo, complains that he is shrinking from hunger, and then realizes that “His world had caught sight of the strange world and was running away.”
We then cut to the invaders, who are humans. The original characters, we come to find out, are microscopic symbiotes who live in the bloodstream of huge, bear-like creatures. The human colonists (“These world-size invaders came inside a superworld of their own” and who came not from outer space, but from outer outer space. Get it?) have to exterminate these radioactive bears in order to make the world habitable. War ensues with the humans releasing a biological weapon, which the endos promptly eat – this causes Raldo to grow so much that he splits into two Raldos, who spend the rest of the story bickering, each suggesting that the other should commit suicide. The world of the Raldos is captured during their counter-attack on the human settlement, and they become the representatives of their people in negotiating with the humans: “Why did you come to this part of space? It has belonged to us from the time our ancestors were mindless, free-floating protozoans. It is still ours.”
Symbiosis is suggested as the answer to everyone’s problem – humans get to see the end of loneliness and ill health, endos get to go to the stars. Everyone wins.
I think this is the first humans-as-alien-invaders story, although the colonialist setup of Matheson’s “Lover, When You’re Near Me” certainly hinted at that as the back story.