Simultaneous acquisition of multiple languages to a native level of fluency is common in many areas of the world. This ability must be represented in any cognitive mechanisms used for language. Potential explanations of the evolution of language must also account for the bilingual case. Surprisingly, this fact has not been widely considered in the literature on language origins and evolution. We consider any array of potential accounts for this phenomenon, including arguments by selectionists

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... the basis for language variation. We find scant evidence for specific selection of the multilingual ability prior to language origins. Thus it seems more parsimonious that bilingualism "came for free" along with whatever mechanisms did evolve. Sequential learning mechanisms may be able to accomplish multilingual acquisition without specific adaptations. In support of this perspective, we present a simple recurrent network model that is capable of learning two idealized grammars simultaneously. These results are compared with recent studies of bilingual processing using eyetracking and fMRI showing vast overlap in the areas in the brain used in processing two different languages.