sj_zero 3 days ago federation: confirmed
You do have to remember that the climate has changed a lot since civilization was born. The epic of Gilgamesh talks about the great cedar forests of Syria. Northern Europe was a giant chunk of ice. And once a place has ontological inertia, there's only been a few times in history where that changes, such as the bronze age collapse.
If things were reversed, and Siberia and Canadian shield for once ideal places for civilizations, I suspect that they would still be heavily populated today in spite of the weather.