Datu is a title which denotes the rulers (variously described in historical accounts as chiefs, sovereign princes, and monarchs) of numerous indigenous peoples throughout the Philippine archipelago. The title is still used today, especially in Mindanao, Sulu and Palawan, but it was used much more extensively in early Philippine history, particularly in the regions of Central and Southern Luzon, the Visayas and Mindanao. It is a cognate of the title ratu in several other Austronesian languages. Overview In early Philippine history, datus and a small group of their close relatives formed the "apex stratum" of the traditional three-tier social hierarchy of lowland Philippine societies. Only a member of this birthright aristocracy (called "maginoo", "nobleza", "maharlika", or "timagua" by various early chroniclers) could become a datu; members of this elite could hope to become a datu by demonstrating prowess in war or exceptional leadership. In large coastal polities such as those in Maynila, Tondo, Pangasinan, Cebu, Panay, Bohol, Butuan, Cotabato, Lanao, and Sulu, several datus brought their loyalty-groups, referred to as "barangays" or "dulohan", into compact settlements which allowed greater degrees of cooperation and economic specialization. In such cases, datus of these barangays would then select the most senior or most respected among them to serve as what scholars referred to as a "paramount leader" or "paramount datu". The titles used by such paramount datu changed from case to case, but some of the most prominent examples were: sultan in the most Islamized areas of Mindanao; lakan among the Tagalog people; thimuay among the Subanen people; rajah in polities which traded extensively with Indonesia and Malaysia; or simply datu in some areas of Mindanao and the Visayas. Proofs of Filipino royalty and nobility (dugóng bugháw) can be demonstrated only by clear blood descent from ancient native royal blood, and in some cases adoption into a royal family. Terminology Datu (Baybayin: ) is the title for chiefs, sovereign princes, and monarchs throughout the Philippine archipelago.<ref name=note1>For more information about the social system of the Indigenous Philippine society before the Spanish colonization see Barangay in Enciclopedia Universal Ilustrada Europea-Americana, Madrid: Espasa-Calpe, S. A., 1991, Vol. VII, p.624: Los nobles de un barangay eran los más ricos ó los más fuertes, formándose por este sistema los dattos ó maguinoos, principes á quienes heredaban los hijos mayores, las hijas á falta de éstos, ó los parientes más próximos si no tenían descendencia directa; pero siempre