Book excerpt: The Punan societies of Borneo, traditionally nomadic rainforest hunters and gatherers, have undergone a transformation over the past centuries. As downriver farming peoples expanded upstream and their cultures and technologies diffused, the Punan gradually abandoned their nomadic existence for a more sedentary life of trade-related activities and subsistence agriculture. But the culture that has emerged from these changes is still based on the enduring ideological premises of nomadism. This study, historical in perspective, examines the many factors-ecological, economic, commercial, political, social, cultural, and ideological-that have played a part in this continuing transformation. Foreword by Georges Condominas.