The German linguist Wilhelm Schmidt first linked the West Bird's Head and North Halmahera languages in 1900. In 1957 H.K.J. Cowan linked them to the non-Austronesian languages of Timor as well. Stephen Wurm believed that although traces of West Papuan languages were to be found in the languages of Timor, as well as those of Aru and Great Andaman, this was due to a substratum and that these languages should be classified as Trans–New Guinea, Austronesian, and Andamanese, respectively. Indeed, most of the languages of East Nusa Tenggara and Maluku appear to have some non-Austronesian influence. In 2005, Malcolm Ross made a tentative proposal, based on the forms of their pronouns, that the West Papuan languages form one of three branches of an extended West Papuan family that also includes the Yawa languages, and a newly proposed East Bird's Head – Sentani family as a third branch. Søren Wichmann considers West Bird's Head, Abun, and Maybrat to form a unified family, but does not accept West Papuan as a coherent language family. Timothy Usher, also somewhat tentatively, accepts Yawa and East Bird's Head, but not Sentani, as part of West Papuan itself, so the family can remain under that name. Holton and Klamer do not unequivocally accept the unity of West Papuan, but note that certain proposals linking "West Papuan" groups together may eventually turn out to be fruitful. Ger Reesink suggests that the West Papuan family should be considered an areal network of unrelated linguistic families, noting the lack of adequate evidence for genetic relatedness.
Pronouns
The pronouns Ross reconstructs for proto-West Papuan are, These are shared by the "core" West Papuan families. Hattam reflects only "I" and "thou", and Amberbaken only "thou", "you", and "she". Ross's Extended West Papuan languages have forms in *d for "I" and *m for "we". These are found in all branches of the family except for the Amberbaken isolate. Ross's West Papuan proper is distinguished from Yawa and EBH-Sentani in having forms like na or ni for the second-person singular pronoun.
Comparative vocabulary
Basic vocabulary of two West Bird's Head languages and three language isolates, quoted by Holton & Klamer from Miedema & Reesink and ; these show diverse non-cognate forms among Papuan languages of the Bird's Head Peninsula: Lexical lookalikes between North Halmahera languages and West Bird's Head languages from Voorhoeve, as quoted by Holton & Klamer :
All Papuan languages of East Nusantara have five or more vowels. Abun and Mpur are fully tonal languages, with Mpur having 4 lexical tones, and Abun having 3 lexical tones. Meyah and Sougb are pitch-accent languages. All other languages of the Bird's Head Peninsula are non-tonal. Of all the Papuan languages spoken in the Bird's Head Peninsula, Abun has the largest consonant inventory with 20 consonants, while neighboring Maybrat has the smallest with 11 consonants. Large consonant inventories similar to that of Abun are also found in the North Halmahera languages, such as Tobelo, Tidore, and Sahu.