Peace and love is all well and good until your crops have failed for the third year in a row. Your food stores are empty. You killed and ate all of the livestock last season because there was nothing left to feed them. There's nothing wild to hunt. Your village has resorted to eating anything it can scavenge, even if it's inedible or even poisonous. People are gnawing on their fingers.

And it's like this for your village and your neighboring village and their neighboring village and so on.

Tell me about it when your neighboring villages' adult men are charging down the hill at you, filthy, starving, crazed and screaming at the top of their lungs, axes in hand.