Protomusic and protolanguage as alternatives to protosign

Explaining the transition from a signed to a spoken protolanguage is a major problem for all gestural theories. I suggest that Arbib's unproved "beyond the mirror" hypothesis still leaves this core problem unsolved, and that Darwin's model of musical protolanguage provides a more compelling solution. Second, although I support Arbib's analytic theory, of language origin, his claim that this transition is purely cultural seems unlikely, given its early, robust development in children.