> We also keep talking about this in terms of rejection (being banned, escaping parents etc), but it might well be that they were simply pushed by a reckless sense of exploration, curiosity, and personal ambition. Their world was endlessly new: what is beyond that hill? What is beyond that river? I'll find out, and if it's good, I'll make it mine. After all I'm a teenager, I obviously cannot die.

Right on. There are a lot of instincts humans show in developed society that work great in a hunter-gatherer society, including this one. See also:

-Tribalism

-Territorialism

-Hoarding