The Iban trace their origins to the Kapuas Lake region of Kalimantan. With a growing population creating pressures on limited amounts of productive land, the Iban fought members of other tribes aggressively, practicing headhunting and slavery. Enslavement of captives contributed to the necessity to move into new areas. By the middle of the nineteenth century, they were well established in the First and Second Divisions, and a few had pioneered the vast Rejang River valley. Reacting to the establishment of the Brooke Raj in Sarawak in 1841, thousands of Iban migrated to the middle and upper regions of the Rejang, and by the last quarter of the century had entered all remaining divisions. The most dramatic changes in the past three decades have been abandonment of longhouses and permanent settlement in Sarawak's towns and cities. Iban have lived near other ethnic groups with whom they have interacted. The most important of these societies have been the Malays, Chinese, Kayan and, during the Brooke Raj and the period of British colonialism, Europeans. The dynamic relations between Iban and these societies have produced profound changes in Iban society and culture.