@youmakemefart
Once again you seem to be pointing at stages of development that
are not the starting point of RAND. Trade is a tech that you don't start knowing, so once again trading will only get to a point where it is portrayed like your description when the tech is discovered, which isn't the beginning of the game.
You can't be so shortsighted, for anything's sake, as to can't imagine humanity before Trade. Which is true to the initial stages of your civilization in RAND.
If you think Trade implies in a migration policy that isn't the starting one created by afforess anymore, then you should defend that the tech Trade enables another migration policy to be used.
Now imagine the tribes of old, where there weren't coins or kings, Chiefdom was the norm, there was few/no Trade between tribes, migrations were to abandon sites and/or to find new ones:
-What was wealth and status to these people?
-Exploitation? In a tribe that hunts, fishes, cuts wood, mines some hills?
-Over hunting or overfarming? I can't see why people would move because of "overfood", only for lack of food.
-To settle another area? Or to join another village? Isn't that more like a random event tied to an early invasion?
-safety and favorable geography once again seem to be better as random events and settlers
-Once more, random events or settlers for climate
-religious or spiritual reasons can also be portrayed by random events and settlers
-adventure?
So if Trade originated around 150,000 BC, then I think we should rework the techtree because AND making it available only after 6000 BC is a shot in History.
Now just to make things clearer, as I think you didn't comprehend from the beginning. Discoveries from realities of long ago are really hard to accurately portray several things because the evidence that remains is small. But, we may presume humanity has stages of evolution similar in many places of different times. If we check the history of Native America, we may see several stages of development at the same time in different locations, being the least advanced that of the amazonian and the tribes along the coast of Brazil and Argentina. There you see Trade as something rare. This brings a lot of knowledge without needing to know from when the first humans started to engage in migration routes.
RAND puts us in this primal state in 6000 BC. In the real world that wasn't the case.
Also it's a civic, a policy, not exactly the behavior of the ones living wherever they live. It's just that the government (in the case of the starting point of RAND, a tribal Chiefdom) doesn't care if you migrate or not, and if people come to the tribe from migration or not. It's not something thinked or developed, it's just one big
I Don't Care to migrations. Of course in the evolution of society, these migrations appeared, but when was the local government first interested in controlling migration?
So the civic is more like Restricted Borders: Travel is dangerous and most people live and die without going too far. That's true for the stage of development RAND implies in 6000 BC at the starting point of the game.