An intentional-historical formalist definition of poetry such as the one offered in Ribeiro (2007) inevitably raises the question of how poetry first emerged, and why. On this view, repetitive linguistic patterning is seen as a historically central feature of poems, and one that has both an aesthetic and a cognitive dimension. Combining the Darwinian idea of a musical protolanguage with analyses of ‘babytalk’, I suggest that this central feature of poetic practices first emerged as a vestige of our musical proto-speech and of our earliest form of communication with our caregivers. Conversely, I suggest that the existence and universality of ‘babytalk’, together with the universality, and antiquity of poetic practices, argue in favor of the musilanguage hypothesis over its competitors, lexical and gestural protolanguage. One consequence of this proposal is a reversal of how we understand poetic repetition: rather than being justified in terms of the mnemonic needs of oral cultures, it is now understood as an aesthetically pleasing exploitation of features already found in speech.