Many story experts maintain that there are “eternal plot structures” that have always existed and always will. But there is evidence from history that those experts are wrong.
Closer at hand, there is other evidence that also contradicts the “eternal plot form” hypothesis, including the endless evolution of audience expectations—which can be seen even as groups of children “age out” of summer camp!
Enter the Summer Camp Ghost Story
Think about the campfire ghost story, as applied in summer camps. When a bunch of 12-year-olds, for example, are gathered around a campfire at night, a camp counselor might say, "Who wants to hear a ghost story?"
In near-perfect unison, the 12-year-olds around the fire say, "I do!" Their faces show anticipation but also bravado, as though they are all saying, "I like to be scared. But you can't really scare me!"
The Story Itself
Because it's a ghost story, of course, the events of the story benefit from taking place in a not-too-safe environment: on a camping trip, say, or in an expedition into an abandoned building.
Once the story begins, one of the story's characters typically suggests that where they are is more dangerous than most in the group take it to be. But those who suggest turning back are overruled. So the expedition proceeds.
Eventually, something spooky happens. How spooky? It depends on the age of the listeners and the goals of the storyteller.
In any case, the spookiness inevitably builds—until it erupts into something "terrible" (and the definition of "terrible" also depends on the ages and sensibilities of the listeners and the storyteller).
The ending may be a "jump" (where the teller suddenly screams, say, or leaps toward the listeners). Or it may be a caution, followed by an indication that the horror of the events still lingers on: "And they were never heard from again. But once in a while, on a rainy, moonless night, you might still hear the moans of the ...."
There can be many kinds of variations in ghost stories. The "ghost," for instance, may turn out to be something harmless, like the sound of a branch blowing in the wind. Or the events might be construed as unexplainable—except as an incursion of the supernatural.
The summer-camp ghost story, then, follows a set of general expectations. The details can vary—and, to avoid being too predictable, they may need to vary from other such stories. But the overall shape of this genre remains much the same.
Do ALL Genres Remain the Same?
The camp counselor has an advantage that writers of novels (for example) don't have: each summer, a new group of 12-year-olds appears. This new group has not heard enough ghost stories to grow tired of them, so the same stories can be told and retold.
Unlike ghost stories at campgrounds, though, the audiences for most other kinds of stories don't listen to a dozen stories of one kind—and then move on to other forms of entertainment.
Instead, readers of novels or watchers of TV shows demand sustained novelty. What was once a surprise (in last year's stories) now becomes predictable—and is, therefore, less interesting. So the readers or viewers won't be satisfied (in the long term) with a string of stories that are too similar to each other.
To "stay the same," most genres need to change!
To have the same impact on repeat listeners, subsequent stories need to defy (at least a little) the usual expectations. When that happens successfully, the new features of successful stories are also imitated and repeated—until, over time, they, too, become too familiar to be fully engaging.
In short, for a genre of stories to continue to have the same effects on the same people, the stories need to change. The new changes will, in time, become familiar—so they, in turn, will also need to change.
In this way, there is pressure on stories in any one genre to evolve. To get the same result, later stories need to use different strategies and techniques than earlier ones!
For this reason, what works for a while for a given set of listeners or readers, will likely need to change, in order to have the same effect!
That's one reason why:
The idea of an eternal plot form will always be problematic.
The story-creator "never sets foot in the same stream twice," because the expectations of readers and listeners change continuously over time.
The best writers and tellers willingly engage in this process of:
Meeting listener expectations
Setting new expectations, and
Repeating 1. and 2.—not just once, but forever.
Eternal? No way!
In other words, plot is not eternal. Rather, it is part of a dynamic cycle of "create/repeat/change." And that may be the one thing about stories that never changes!