At the local level, individual Malay sultanates all over the archipelago that usually based on rivers and often close to the coast, exercised sufficient attractiveness, or suasion, to foster a process of assimilation. They were operating on a range of frontiers - in Sumatra, Borneo and the Peninsula - where non-Muslim peoples, in many cases the tribal communities, were gradually being brought into Malay realm: learning to speak the Malay language, adopting Islam, changing their customs and style of dress and assuming roles of one type or another within the expanding sultanates. In an early example from eastern Sumatra, the 15th century Sultanate of Aru, believed to be the precursor of Malay Sultanate of Deli, is described in the Melaka-Johor chronicle as being of Batak origin. European observations on the same region from the 19th century suggests that people further upstream on the rivers of Deli, people who had long had a trading relationships with the coast, and were later called Karo Batak, were being incorporated in the Deli Sultanate. The Batak and Malay distinction was not racial but cultural, and by converting to Islam and taking on Malay dress and culture, the Batak could become Malay. Both European and Malay writings show them being tutored in the new culture, receiving Malay titles such as Orang Kaya Sri di Raja as part of the process of conversion. Similar developments were underway in Asahan, to the south, and on the Barus frontier in the northwest of Sumatra where entry to the new sphere entailed not only a change in manners an clothing styles, but also the adoption of the Islamic religion and the Malay language. On the peninsula, the effects of the continued contacts between the non-Malays with Malay-dominated centre is suggested in a 19th-century account of Pahang, which mentions that some of the natives who had strong trading ties with the Malays had begun to emulate their speech and dress. The population of Pattani also has been described as partly aboriginal in origin. In the case of Johor, the aboriginal people who were reported in the 19th century to be speaking Aslian languages, were called 'Malay' a century later. It has been suggested that these people would probably have joined the Jakun first before becoming Malay. The Jakun are described as being similar to Malays in their kinship arrangements, but resistant to aspects of social structure as well as the