Author Jack Vance was such a driven world-creator that I’m beginning to suspect it was less of a talent and more of a compulsion. For a timely example of Vance’s relentless societal construction, take the Planet of Adventure quartet of novels, the middle two books of which are celebrating their fiftieth anniversary this year. The books have already been summarized quite well on this site, but I’ll give you the quick version: Space explorer Adam Reith arrives on the planet Tschai, and discovers that four alien races already call it home. The reptilian Chasch arrived thousands of years ago, followed by their enemies, the pantherlike Dirdir and the hulking amphibious Wankh. There’s also a mysterious race called the Pnume who are indigenous to Tschai. And there are humans—lots of them.
The Dirdir, it turns out, gathered up some neolithic humans when they visited earth tens of thousands of years ago, and have been breeding their descendants into a servant race. The Chasch and the Wankh have joined in, as have the Pnume, creating another quartet of exotic races: the Chaschmen, the Dirdirmen, the Wankhmen, and the Pnumekin. Then there are the various humans who live in the towns and wildernesses of Tsachi who have no alien affiliation, and who have created their own cultures in the shadows of the aliens’ cities.
If you’re keeping score, that’s over half a dozen distinct cultures; when you start reading the books, you soon find even more, as Reith encounters wildly varying societies of humans struggling to survive on the strange planet, some with elaborate customs and cities, others still operating at a caveman level.