The Sepik River Basin within the island of New Guinea is a hotspot of linguistic diversity in terms of established genetic families, numbers of languages, and their structures. Geopolitical factors, including the size of communities, migrations, time depth of human habitation, geographic features of the terrain, means of subsistence, and patterns of ritual and day-to-day multilingualism each play a role in the maintenance of linguistic diversification and fragmentation, alongside constant punctuations. Within the Middle Sepik region, two groups of inhabitants - River Dwellers and Jungle Dwellers - stand apart in their language ecologies and subsistence, and are in a symbiotic relationship, complementing each other. Their shared patterns of ritual and material exchange go hand-in-hand with a tendency towards compulsory differentiation between closely related languages and speaker norms (or 'schismogenesis'). The European colonization and the advent of modernity, including new means of communication and multilingual exchanges, have affected linguistic and cultural diversity.