But you need a really good reason to explore in a survivalist campaign.
The life of a nomadic hunter-gatherer is one of exploration. Game migrates, and hunters migrate with it. Older hunters remember previous migrations; younger ones learn the way.
If you think of prehistoric humanoids as just a little smarter than animals, one doesn't think of animals as very motivated to explore.
Prehistoric Cro-Magnons were presumably as intelligent as modern men; they just weren't educated. Imagine how stupid you'd look in the primeval forest of Europe with no idea what to eat, how to track prey, what to call various plants, etc.
I'm talking about campaigns where "Me get food, me get shelter, me procreate" is as high as things go on Maslow's Hierarchy of Needs for now. You could get a tribe to explore by forcing a move due to the the food source drying up or a natural disaster/Ice Age, but it's all tied to basic survival.
It's terribly un-PC, but raiding other tribes for women might make for good adventures. It obviously continued well into Bronze Age Greece.