Evolutionary Stasis

So, you have a dystopian epic set millions or billions of years in the future. It's safe to assume that there are still humans, and possibly other organic life forms, still reproducing.

One would think that, even if natural selection has ceased to be a factor because of a static environment, mutation and genetic drift would still be factors. Even the proponents of Designer Babies rarely intend to micromanage everything. (Genetic drift will happen in the parts that aren't.) And even cloning gets mutations. And if any other species has survived, then they should be affected by evolution, too.

But writers tend to ignore any possible evolution unless it's directly related to the plot. It may be on purpose, to save the trouble of imagining new species; World Building is a major distraction from writing, after all. And it's commonly believed that humans as we know them are more relatable than barely recognizable humanoid beasts who don't even resemble any other known species. (The ones that do resemble known species generally have undergone an Anthropomorphic Shift, which generally did not happen naturally...) A nonhuman human might as well be an alien...

Or maybe the writers Did Not Do the Research. Even if the fact that there will be genetic changes is possible to research, the nature of the changes would be a good deal harder.

See also Medieval Stasis.

Anime and Manga

 * Now and Then Here and There is set 5 billion years in the future and humans haven't changed at all. Now, it's possible the human population was brought to the future by the 'bound' system, but that's never implied in the series.

Comic Books

 * Johnny Future, from Alan Moore's Tom Strong, lives in an age when the Sun has become a red giant, yet he looks perfectly human.

Literature
"To the south of them the Picts remain savages, apparently defying the laws of Nature by neither progressing nor retrogressing."
 * The Underland Chronicles averted in that the underlanders' eyes turned purple and their hair turned a very light blond. Although how living under ground could cause a change in melanin levels that quickly could be an example of Did Not Do the Research
 * Discussed and arguably justified in Isaac Asimov's The End of Eternity. Twissell, from beyond the 30,000th century, is virtually undistinguishable from a modern human (to make no mention of, who's from beyond the 100,000th century and still there's no way to tell). Twissell is convinced that this stagnation is due to some machination from beings in the future, but it's revealed that has deprived mankind of any evolutionary drive.
 * In Robert E. Howard's "The Hyborian Age", the Backstory of Conan, he inverts this, regarding cultural evolution as fixed, the failure of which, even in a short period of time, needs explaination.


 * But he seems to think that evolution is a one lane road that life can go both ways, but never adapting into new branches. In his world humans repeatedly regress back into apes, and then evolve to humanity again. Conan's ancestors were Atlanteans who became apes who became people, for example.
 * In The Hitchhiker's Guide to the Galaxy, it is mentioned that the Vogons stopped evolving shortly after they stopped being an aquatic species. The planet Vogsphere has created many other life forms far more appealing than the Vogons, which they inevitably destroy for their own amusement.

Live Action TV

 * In the BBC series Jekyll, the antagonists justify their attempts to kidnap Tom Jackman and experiment on his other personality on the basis that humanity is doomed to Evolutionary Stasis without Hyde's unique genetics.
 * Doctor Who:
 * In "New Earth" and "Gridlock", taking place 5 billion years in the future, pure humans are extinct, but the descendent species look identical.
 * In "Utopia", taking place trillions of years in the future, humans still look identical. At some point in between they spent time as clouds and data, but they apparently keep returning to human form.

Video Games

 * Played straight in Chrono Trigger. Humans haven't changed one iota in 65 million years aside from the development of magic, and there's a number of other species that haven't changed at all either except for color.
 * Well, there were a handful with tails in the prehistoric era, and blue hair seemed common among magic users in 12,000BC but is not present in the "modern" era (the magic users may in fact have defied the trope and "evolved" into the magic using monsters on the other continent).