In 1890 the Dutch colonial government banned cannibalism in the regions under their control. Rumors of Batak cannibalism survived into the early 20th century but it seems probable that the custom was rare after 1816, due partially to the influence of Islam. Tarombo Family tree or lineage is a very important thing for the Batak, as those who do not know the lineage will be considered as a strayed (nalilu) Batak. Batak people are required to know their lineage or at least the ancestors of which the family name (Marga (Batak)) and the related clans (dongan tubu) came from. This is necessary in order to determine the relation of a kinship (partuturanna) within a clan or simply the surname (Marga (Batak)) itself. Geography The Batak lands consist of North Sumatra province, excluding Nias island, the historically Malay kingdoms of the east coast and the western coast of Minangkabau people. In addition, part of the Karo lands extend into modern-day East Aceh Regency in Aceh province, while parts of the Mandailing lands lie in Rokan Hulu Regency in Riau. Significant numbers of Batak have migrated in recent years to prosperous neighbouring Riau province. To the south of North Sumatra are the Muslim Minangkabau of West Sumatra, while to the north there are various Muslim Acehnese peoples. Traditional Batak religion The various Batak cultures differ in their pre-colonial religious ideas as they do in many other aspects of culture. Information about the old religious ideas of the Mandailing and Angkola in southern Batakland is incomplete, and very little is known about the religion of the Pakpak and Simalungun Batak. For the Toba and Karo on the other hand the evidence in the writings of missionaries and colonial administrators is relatively abundant. Information on the traditional forms of Batak religion is derived mainly from the writings of German and Dutch missionaries who became increasingly concerned with Batak beliefs towards the end of the 19th century. Various influences affected the Batak through their contact with Tamil and Javanese traders and settlers in southern Batakland, and the east and west coast near Barus and Tapanuli, in particular the large Padang Lawas temple complex in Tapanuli. These contacts took place many centuries ago and it is impossible to reconstruct just how far the religious ideas of these foreigners were adopted and reworked by the Batak. It is suggested that the Batak adopted aspects of these religions,