The smallest definition of a tribe is usually 500 people. They can be 10 tines that size. Tribes did not exist until about 10,000 years ago. They were preceded by hunter-gatherer bands.
The inland Papuan group most associated with violence are the Enga, but they are not migratory hunter-gatheree bands. They are farmers who grow sweet potatoes and raise pigs.
What I argued is that whenever two competing groups came into contact, wanting the same land, the result was usually genocide (or one of the groups fled to another area, where they would have to fight those inhabitants), and as a result, when history records a new group "inhabiting" or "settling" a peace of land that is new to them, then that inhabitation is generally not peaceful, but genocidal in nature. Regardless of whether there is a written history to record the violence, we can have confidence that the violence did occur.
Now, given that modern humans have been around for 300,000 years at least (the date keeps being pushed back, since before the Moroccan discovery, it was thought to be 100,000 years), and have been swarming over the whole earth, that is a lot of violence and genocide, even though it was certainly possible to live a life of peace as well for a specific individual, since migrations weren't going on all the time in all places.
There is little evidence of behavioral modernity - cave paintings, Venus figurines, hearths, burials etc. prior to 50,000 years ago. There is some evidence so the time could always be pushed back.
Farmers compete for land. Migratory hunter-gatherers are just passing through, so there is less competition for land. Also, bands usually mate with nearby bands, who are often more distant relatives.
There has not been much evidence of hunter-gatherer bands clashing violently then or even in modern times, including observations over past centuries. There is a plethora of evidence of post-neolithic farming and then industrial societies being this way.