"Similarly, the Malay population of the coastal low- lands of Malaya, Sumatra, and Borneo gradually absorbed animist hill peoples during the five centuries before 1900, by a mixture of raiding, tribute, and purchase, especially of children... . Around 1500 Java was the largest single exporter of slaves, perhaps as a result of the divisive wars of Islamization. Through the still Hindu ports of Sunda Kelapa and Balambangan, Java supplied much of the urban working class of the Malay cities. Islamization created a major change in the nature of slave trading, since the shari'a law forbade the sale or enslavement of fellow Muslims. Once Islam completed its conquest of Java in the sixteenth century, that island ceased to export its people. The major Muslim cities were thenceforth supplied with slaves from beyond the frontier of Islam. Aceh obtained its servile labour from Nias, southern India, and Arakan; Banten and Makassar from the Moluccas and Lesser Sunda Islands; Patani from Cambodia, Champa, and Borneo. Certain small sultanates, notably Sulu, Buton, and Tidore, began to make a profitable business of raiding for slaves in eastern Indonesia or the Philippines and marketing the human victims to the wealthy cities-or to the expanding seventeenth-century pepper estates of southern Borneo."