History. It’s happened before, and it’ll keep happening as long as there’s a present, and a future, and time to reference them… I’m trailing off here. History is an important part of world building when writing. Without it, why does everyone act the way they do? Why does one culture have dominance over another? Why do two people hate each other? And why can’t I find more than two people in this world that don’t like pasta? Okay, so maybe that last one wasn’t so relevant, but still(!), you people must exist.
Anyway, that aside, what happened in your world? Every writer usually has intricate detailed notes about one thing and then another, and how it all works together in some kind of tug-of-war web. (Actually, that could be pretty fun…) What were the earlier cultures? What religions spread, and how? What wars were there?
I feel like I’m not really doing the topic justice, but so many things influence history that it’s hard to detail it all. Technology, Beliefs, Government, International Relations, Social Trends/Movements, Location, Resources, etc… They are all things to consider, so don’t leave them out if you want your world to come to life.
Where would we be without Abraham Lincoln? Martin Luther King? What about Women’s Rights Movements? Let’s go further back. What if Greece never developed a Democracy? What if the Puritans stayed in England? What if the Native Americans drove us away? More currently, what if Mexico’s Drug Lords were, instead, Canadian? Imagine how that would change the world? Pick up a Steampunk novel set on Earth. Pick up a Wild Cards novel. They add one event, or alter the path of something, and change the world completely.
Keep it in mind when you write. There’s always a story as far back as there were people, and before that if you look hard enough.