While you are a nomadic tribe, you have two advantages:

1. You get massive influence by killing, regardless its animals or AI armies. 10 influence per AI tribe you kill. I managed to build 8 outpost, occupying completely the southern/eastern coast, plus nearly 1000 influence at roughly round 30. Considering how slow you generate influence after ancient era, staying at nomadic era will help your early expansion.

2. You get insanely large army. Having 2 tribes killing a mammoth instantly grant you 2 new tribes. Therefore you can "duplicate" your army simply by killing. Even more, I kill every AI army on sight and ransack their outposts on sight. That way 2 AI just get wipped away before ancient era (they never enter ancient era. Whenever a new army spawn, I kill it immediately; they will never get even a single star; as a result, it shows I have never met them). At the end of nomadic era, I have 78 units and population, which is impossible if you build all your armies in cities. These tribes will turn to scouts immediately and as long as I keep killing everything I see, it's impossible for AI to get any technologies and I do not need to build any military units afterwards.

3. Probably a bug, if you do not enter ancient era, they AI will not enter it either (though you know they are already in the ancient era as you can not attack their city, showing you must declare war. You can not declare war since you are still in nomadic era)

As a result, I entered ancient era at roughly round 20 with 8 outputs. I immediately unlocked several technologies as you accumulate science even if you are in nomadic era. I entered classical era at round 30 and medieval era at round 40.

I attached some photos of the time I decide to go to ancient era. You can see I control the continent during nomadic age