[@6slyboy6]Handwaving is fine, especially for our purposes. 100 is about the size of a typical hunter-gatherer band, so that seems perfect. In more tropical places, sedentary civilization with low/no agriculture (hunter gatherer lifestyle) would be feasible because there are more food resources laying around. Also less incentive for large-scale agriculture. Somewhere like the grasslands or more temperate/colder forests not so much.

If there are any river basins with populations of animals that would be iseful to domesticate and warmer but not tropical climates, that's probably where agriculture happens first.

Not that that much consideration needs to be taken, working with non-humans can certainly be different. 

That one to the southeast* of the mountain range comes to mind, and the adarnians.