Nobody really knows where the native peoples of Sarawak come from.
Originating in the north, they probably swept gradually down the Malay peninsula and across to the islands some 4,000 years ago, absorbing or displacing the races who lived there. These previous races now survive only in isolated areas, such as in the hilly interior of Malaya, the upland forests of the Philippines, and in parts of the Indonesian archipelago. Their economies and societies adapted to meet a variety of different conditions. Along the swampy coasts, societies like the Melanau developed a way of life based mainly on fishing and the collection of swamp sago. Away from the coasts, these peoples used land mainly for swidden agriculture, originally of root crops, supplemented by forest sago.