People living in an undomesticated nature are almost by definition 'wild', and uncivilized people. It will be important to differentiate between between those who have come to Siberut as voluntary migrants and those who have been officially transferred to the island as civil servants. It is inhabited by about 23,000 Mentawaians and a small number of migrants, predominantly of Minangkabau origin. Siberut has been an oceanic island for at least 500,000 years and its fauna and flora have evolved in isolation from the dynamic evolutionary events on the Sunda Self. Hills rise steeply, though the highest peak on the island is less than 400 meters.
Many rivers dissect through the thick forest.
The Mentawaians are traditionally organized in patrilineal groups of approximately 30 to 80 people living in small settlements, called uma , along the banks of the rivers. These groups of people were autonomous political units. There was a high frequency of marriages between uma members living in the valley of a particular river, but political units were never formed at that level. The size and density of the population must have been rather stable for a long period. Hunting, fishing and gathering provided most of the daily food.