Most societies had ways of limiting the damage of warfare. They evolved over centuries or more and worked.
New Guinea had a lot of wars and a lot of ways of making truces. Their wars typically weren't as bloody simply because arrows aren't usually as lethal, esp. in wooded areas, as guns.
On the other hand, most such truces weren't long-term stable. They may go for a year. They may go for 50 years. But they usually break down over transgressions involving land, game, water, or women. Or simple honor. Humiliation could be borne as long as it can't be reclaimed, but once you're powerful enough to plausibly reclaim it you eventually have to do so. The definitive way of resolving a war was genocide. And New Guinea as traditionally had a really high genocide rate. Kill off all the males over a certain age and claim the women as your tribe's.
That's actually humanitarian in an odd sort of way, if "humanitarian" means 'minimize the loss of life'. If you kill 200 adult males in a genocide that can easily be fewer deaths than if every 20 years you kill 40 males and the war goes on for over 100 years.
= new reply since forum marked as read