[1][2] Unlike almost other Western Oceanic languages of New Guinea, which are spoken exclusively in coastal areas, many Markham languages are spoken in the mountainous interior of Morobe Province, Papua New Guinea, where they are in heavy contact with Trans-New Guinea languages.
A phonological reconstruction of Proto-Markham is presented in Holzknecht (1989) and is summarized below.
[1] Labu (= Hapa) Proto-Markham was reconstructed by Susanne Holzknecht in 1989 in her paper The Markham Languages of Papua New Guinea.
It descends from Proto-Huon Gulf on the basis of shared phonological, morphosyntactic and lexicosemantic innovations, such as the merger of Proto-Huon Gulf *t, *r, and *R as Proto-Markham *r, the accretion of *ka- into focal pronoun bases (Proto-Oceanic *kamu "you" > Proto-Markham *ka-gam "id.
"), and the replacement of Proto-Oceanic *qacan "name" by Proto-Markham *biŋa "id.