Negrito, proto-Malay, and Malay peoples were the principal peoples of the Philippine archipelago. The Negritos are believed to have migrated by land bridges some 30,000 years ago, during the last glacial period. Later migrations were by water and took place over several thousand years in repeated movements before and after the start of the Christian era.
The social and political organization of the population in the widely scattered islands evolved into a generally common pattern. Only the permanent-field rice farmers of northern Luzon had any concept of territoriality. The basic unit of settlement was the barangay, originally a kinship group headed by a datu (chief). Within the barangay, the broad social divisions consisted of nobles, including the datu; freemen; and a group described before the Spanish period as dependents. Dependents included several categories with differing status: landless agricultural workers; those who had lost freeman status because of indebtedness or punishment for crime; and slaves, most of whom appear to have been war captives.
Islam was brought to the Philippines by traders and proselytizers from the Indonesian islands. By 1500 Islam was established in the Sulu Archipelago and spread from there to Mindanao; it had reached the Manila area by 1565. Muslim immigrants introduced a political concept of territorial states ruled by rajas or sultans who exercised suzerainty over the datu. Neither the political state concept of the Muslim rulers nor the limited territorial concept of the sedentary rice farmers of Luzon, however, spread beyond the areas where they originated. When the Spanish arrived in the sixteenth century, the majority of the estimated 500,000 people in the islands still lived in barangay settlements.