https://arstechnica.com/science/2025/07/what-fanfic-can-teach-us-about-cultural-evolution/

This is NOT generalizable to mass culture. But it is suggestive.

It’s a good overview of fanfic for those who do not know it AND it is an example of data driven sociology-anthropology.

“really is a mystery how we evolve at all culturally; it’s not happening by gradual movement. We can see that there’s novelty. We can see that when people encounter novelty, they enjoy it. But we can’t quite make sense of how these two competing effects work out.”