The early polities of the Philippine archipelago were typically characterized by a three-tier social structure. Although different cultures had different terms to describe them, this three-tier structure invariably consisted of an apex nobility class, a class of "freemen", and a class of dependent debtor-bondsmen called "alipin" or "oripun." Among the members of the nobility class were leaders who held the political office of "Datu," which was responsible for leading autonomous social groups called "barangay" or "dulohan". Whenever these barangays banded together, either to form a larger settlement or a geographically looser alliance group, the more senior or respected among them would be recognized as a "paramount datu", variedly called a Lakan, Sultan, Rajah, or simply a more senior Datu. Eventually, by the 14th to 16th century, inter-kingdom warfare escalated and population densities across the archipelago was low.