(Good link, Jno!). Bubu, put it down to the arrogance of historians who consider that real civilisation has only come about since writing was invented, and anything before that must have been positively Neanderthal.
In a low-population hunter-gatherer society, people tend to get on with each other. Sure, there might be some clobbering if things are scarce, and another bunch try to move in. But if you're 'just passing through, folks' you'd be welcome to do so, and while you're here, what's the news from where you come from?
(Notice how all those pre-historic fortifications only came into being once agriculture had become established?)