This paper examines possessive marking in Pidgin Fijian as an example of morphological simplicity in a restricted pidgin. This is attributed to a process of simplification or lack of development in early second language acquisition. Here the only effect of the substrate languages appears to be in constituent ordering. The paper then goes on to look at morphological expansion in possessive marking in an expanded pidgin (or according to some, a creole): Melanesian Pidgin (MP). This is attributed to functional transfer from the substrate languages in extended second language use. While many core features of the Central Eastern Oceanic substrate are found in MP, the overt marking of alienable versus inalienable possession is not. One explanation is that this feature is "functionally expendable" or "inessential" in language (McWhorter 2002). However, the paper argues that the absence of formal marking of the alienable-inalienable distinction in MP can be best accounted for by availability constraints that prevented transfer of this feature at an earlier stage of development.