This paper examines morphologically conditioned vowel elision processes in Aymara, and proposes that they are due to a two-way division in Aymara suffixes between those which delete a mora from the preceding morpheme and those which do not. This “dominant/recessive” morpheme analysis builds on and simplifies previous accounts, which specified a preference for consonantal or vocalic environment on both sides of each suffix. I observe some phonological tendencies within suffix categories and propose a diachronic hypothesis as to how morphological vowel elision could have evolved from purely phonological vowel weakening processes that are still found in the language today.This paper examines morphologically conditioned vowel elision processes in Aymara, and proposes that they are due to a two-way division in Aymara suffixes between those which delete a mora from the preceding morpheme and those which do not. This “dominant/recessive” morpheme analysis builds on and simplifies previous accounts, which specified a preference for consonantal or vocalic environment on both sides of each suffix. I observe some phonological tendencies within suffix categories and propose a diachronic hypothesis as to how morphological vowel elision could have evolved from purely phonological vowel weakening processes that are still found in the language today.