How sovereignty developed?

Georges Dumezil thought that in proto-Indo-European ancient history sovereignty was comprised of the shared rulership of a Magician-King, in concert with a powerful Jurist-Priest, and all were protected by warriors---then IE society rested on the shoulders of provider farmers. This was the Trifunctional hypothesis.

I have not done the serious scholarship of Dumezil but I speculate that originally there was one warrior sovereign leader of a small group, a total leader, a warrior-priest-lawmaker. As he became older and presumably wiser he delegated warrior duties to his son, or someone like a son, but he kept the priest-law duties for himself. This was a preliminary dual leadership, but when the old man died the son became once again the sole warrior leader-priest etc., assuming he could retain the post.

Over time as groups became larger they simply became too large for one man to be sovereign of all things, and this is when a dual sovereignty began between priest and warrior. But it was an uneasy sovereignty. If you have ever seen the old classic John Ford Western, “The Man Who Shot Liberty Valance” you may remember the very uneasy relationship between the law of the gun in the old West (John Wayne) and the new coming laws of statehood (James Stewart). In Indo-European history it was mainly to calm the problems between the dual leadership of priest and warrior that the “King” was eventually appointed, who then had the final say in things, while still keeping the warrior, priest, and the other castes. Modern sovereignty and modern castes developed out of this.

This seems simpler and more likely than a period of shared sovereignty between a Magician-King in concert with a powerful Jurist-Priest. And it would probably apply to societies other than Indo-European as well... Of course scholarship would need to affirm this speculation.