These new trade routes are amazing. It'd be great if Tarn sat down with a historian and discussed how these things usually form and sustain themselves in real life.
It seems like there's a maximum distance between "hubs" beyond which there will be no trade... look at the isolated little group of cultures in the far right of medium region 1. I understand the typical hamlet/town trade, where raw materials come in to the city and then finished goods go back out, but when it comes to trade between city hubs I wonder what criteria the game uses to decide where to set one up and what those cities are going to be trading. For example, if that little country on the other side of the world has some rare kind of plant or metal, will cultures eventually set up a much longer trade route? Will cultures that trade directly to faraway lands, cutting out the middleman, get a better deal on the merchandise than cultures that rely on an extended trade network where distant goods must change hands many times?
Also, I wonder how trade routes are set up in world gen, how static they are over time. Are they recalculated every year, or every century? If a town expands its hamlets and gains access to a kind of resource, will it cease its trade with a distant town which previously was providing them that resource? Is there a concept of discovery, where a culture might have too little information about another culture and so would not be able to trade with them, or are all cultures assumed to be aware of the relative availability and value of goods all over the world?
This stuff is just really interesting to me.