The Taiap village of Gapun is located on a hill that was historically an island a few thousand years ago when the current mouth of the Sepik River had been inundated by the sea (the Nile Delta had also undergone similar historical processes). Foley speculates that Taiap could have been part of a larger language family that was spoken on the island before the arrival of Lower Sepik speakers. As the coastline moved further northeast, Lower Sepik speakers migrated from the foothills into the new land areas created by the receding waters.
Although Donald Laycock (1973) placed Taiap in his Sepik Ramulanguage family, its structure and vocabulary would be unique for that family, and Ross (2005) found no evidence that it is related to any language of New Guinea. The current extent of Taiap is nearly coincident with what had been an offshore island 6,000 years ago, consistent with the idea that Taiap is a language isolate.
^ abcdeFoley, William A. (2018). "The Languages of the Sepik-Ramu Basin and Environs". In Palmer, Bill (ed.). The Languages and Linguistics of the New Guinea Area: A Comprehensive Guide. The World of Linguistics. 4. Berlin: De Gruyter Mouton. pp. 197–432. ISBN978-3-11-028642-7.
^Wichmann, Søren. 2013. A classification of Papuan languages. In: Hammarström, Harald and Wilco van den Heuvel (eds.), History, contact and classification of Papuan languages (Language and Linguistics in Melanesia, Special Issue 2012), 313-386. Port Moresby: Linguistic Society of Papua New Guinea.
Donald C. Laycock. 1973. Sepik languages - checklist and preliminary classification. Pacific Linguistics B-25. Canberra: Pacific Linguistics.
Donald C. Laycock and John Z'graggen. 1975. "The Sepik–Ramu phylum." In: Stephen A. Wurm, ed. Papuan languages and the New Guinea linguistic scene: New Guinea area languages and language study 1. Pacific Linguistics C-38. 731-763. Canberra: Pacific Linguistics.
Malcolm Ross. 2005. "Pronouns as a preliminary diagnostic for grouping Papuan languages." In Andrew Pawley, Robert Attenborough, Jack Golson and Robin Hide, eds. Papuan pasts: cultural, linguistic and biological histories of Papuan-speaking peoples. Pacific Linguistics 572. 17-65. Canberra: Pacific Linguistics.