area since late 13th century. Despite among the earliest Sumatran kingdom that was exposed to Islam, the people of Aru kingdom remained predominantly pagan, especially those who inhabit interior region. The successor state of Aru Kingdom was the Sultanate of Deli, which demonstrate a mixed influences of Karo, Malay, Tamil, and Aceh. Today, the religion of Karo people are mostly Christian, a religion brought to Sumatra in the 19th Century by missionaries. However, an increasing number living away from the Karo Highlands have converted to Islam, with the influence of Muslim Malay from neighboring Deli area in Medan, and Javanese immigrants, thus making the traditional habits of pig farming and cooking less common. Some Muslims and Christians however still retain their traditional animist beliefs in ghosts, spirits (perbegu), and traditional jungle medicine, despite that fact it contradicts their other beliefs. The Gereja Batak Karo Protestan or Karo Batak Protestant Church is the largest church among the largely Christian Karo people of North Sumatra, Indonesia. This tribal congregation was established formally in 1941 as a Reformed-Calvinist church. The church has 276,000 members (as of 2006) in 398 congregations with 196 pastors. Member of the World Communion of Reformed Churches. Karo people traditionally lived in shared longhouses also called "rumah Siwaluh Jabu", but very few now remain (one in Desa Lingga, Karo district), and new construction is exclusively of modern designs. It is believed that Karo people may have migrated from the other lands in order to take part in trade with the visiting Tamils. This intercourse had an influence on their religious beliefs, as well as ethnic makeup, the marga 'Sembiring', meaning 'black one', and many Sembiring sub-marga (Colia, Berahmana, Pandia, Meliala, Depari, Muham, Pelawi and Tekan) are clearly of South-Indian origin, suggesting that inter-marriage between Karo and Tamil people took place. Religion Traditional beliefs Christianity The Karo were harassing Dutch interests in East Sumatra, and Jacob Theodoor Cremer, a Dutch administrator, regarded evangelism as a means to suppress this activity. The Netherlands Missionary Society answered the call, commencing activities in the Karolands in 1890, where they engaged not only in evangelism, but also in ethnology and documenting the Karo culture. The missionaries attempted to construct a base in Kabanjahe in the Karo highlands, but were repelled by the suspicious locals. In retaliation the Dutch administration waged a war to conquer the Karolands, as part of their final consolidation of power