Human Galactics

The point of Poul Anderson's "Details" is that history is chaotic.

The point of his "Backwardness" is that a high average IQ was not necessary for human survival or technology.

The point of his "Soldier from the Stars" is that militarily superior humanoids would be able conquer Earth by destroying much of it but they would be better advised to sell their military services to the highest bidder among Terrestrial governments, thus conquering Earth economically.

In "Details," extra-solar "human beings" able to pass as Terrestrials observe and subtly intervene on Earth. In "Backwardness," human beings from Earth-like planets where evolution exactly parallels that on Earth land to negotiate with the UN. In "Soldier from the Stars," the aliens, as far as I can remember without having reread that story recently, orbit Earth and offer their services. But they are close enough to human beings to live here, buy property, invest etc.

In each of these short stories, Anderson, in order to make his particular point, makes, for story purposes,  the impossible assumption of human beings from the stars. But he speculates seriously about extraterrestrial and extra-solar life in other works.