Cavemen should have “intrinsic cave awareness” - meaning that they “just know” the layout of the floor they’re on. This could be implemented a couple ways: auto-mapping the rooms on the level but not the corridors when you get within a certain distance; giving you a sort of persistent, limited clairvoyance which maps any walls within a certain radius of you (but not any floors, corridors, or other terrain) every turn, or being able to see walls in line of sight at any distance - but not the floor between you and the wall, if it’s dark.