I’d like to put forth the thesis that tribalism was a primitive form of PDA/DRO.
Modern-day Somali tribes are essentially mutual-aid organizations based on kinship relations. Every member of a Somali tribe has at least one other member who serves to insure him in his disputes. He also has a fellow tribesman appointed as a judge (oday). Should he ever be in a dispute, this oday will sit on the court that judges it.
A Somali’s tribe has the right to disinherit him should he continue to commit offenses or fail to abide by a sufficiently severe judgement against him. However, it doesn’t appear that a Somali can voluntarily leave the tribe of his birth and join another one.
Based on the contemporary Somali model, I submit that ancient tribes were typically the same way. The details may have differed, but tribes seem to have served the purpose of a PDA and DRO put together. They protected members (and their property) from harm, both actively and through insurance, and also helped to settle their disputes.
Tribes typically occupied specific territories. One could say, then, that a given tribed owned the land that it occupied. In many cases, tribes would not allow their lands (or any parts thereof) to be sold to other tribes. To be honest, I’m not sure why this was done.
Sometimes, many neighboring tribes jointly developed standard procedures for settling disputes. Subsequent decisions from those procedures were passed on either orally or literally. This could be known as a legal system for the tribes involved.
However, oftentimes those legal systems were not tied to the members of the tribes directly. They were tied to the territory occupied by the tribes. So if a member of one of those tribes went outside the territory of the legal system, and subsequently became involved in a dispute, he could not appeal to that legal system to (help) judge the dispute.
It seems to me that this is the basis for the idea of a territorial monopoly in law. This monopoly was strengthened when one could not voluntarily leave the tribe of his birth. From what I can tell, the formation of States must have been strengthened by these two principles.
Thoughts?