Worlding Building with off-the-wall logic

No purpose whatsoever beyond that it's a pretty picture.

Look! Clouds in a keyhole building!

Okay, random picture aside. Let's talk "skants."

In Star Trek, The Next Generation, new uniforms were introduced. These included the traditional pant uniform and the dress-like uniform.

The dress-style uniform, which could be worn with or without pants, was available to both genders--according to Star Trek lore, this is a logical extension of total equality of the sexes, allowing all genders to choose whichever uniform pleased them most.

Skants: this Starfleet
uniform style is available
to both genders.
View more here.

Besides being a nice piece of geeky trivia, this is also an example of a exercise to develop a story world, especially when setting books in a later date of an old world. Following the logical trains of events in the first book can lead to some interesting cultural developments.

Did your hero save the world via bombing the evil aliens out of the sky? Maybe her descendants have a fear of the sky. They come up with an official position: the Sky Watcher. A dozen generations later, the Sky Watchers have become fully ceremonial positions, because nothing has come out of the sky. A few more generations, and the senate is debating cutting their funding. They end up underfunded and gain a reputation as lay-abouts, the few people who take the job being those few dreamers who spend too much time with old legends. Then, of course, here comes the evil aliens' descendants, and only your new hero, a young Sky Watcher with little funding and less training is qualified to make contact and stop another invasion... if only someone would listen to him.

What about cultural shifts? In the first series, the Bakers' Guild bribes the senators, and bakers receive first dibs on wheat, before individual families. That makes wheat prices artificially high, which is what drives your original hero to her destined journey to stop the alien invaders, because it'll pay enough to feed her family. Two decades after the world is saved, people revolt against the starvation, electing new senators and forming a new political party. This political party, which prioritizes feeding everyone, does so by taxing and by cutting funding to another area: disaster relief and Sky Watching.

Thus, by the time the aliens return, there are no longer sufficient mechanisms in place to handle the disasters. Natural disasters leave little rebuilding in their wake, and many cities have been lost to various storms, quakes, and landslides. So the hero has grown up in a post-disaster slum, and has a great ability to MacGuyver anything... but absolutely no idea of how to act properly around high-class individuals, such as the senators he's trying to convince to prepare for a new invasion and/or peace-making mission.

You can stretch your logic and your creative thinking all you want, as long as you can back it up. It's part of why I love world-building.

What's a cultural or plot point you've come across that builds off a series set further back in the timeline of the same world?