The emergence of phonological forms
As it becomes increasingly clear that language emerged suddenly in our species over the space of less than 100,000 years, the pressure to understand how the externalization system could have been ‘language-ready’ prior to the emergence of syntax grows as well. Phonology, like other components of language, must then be understood to rely maximally on abilities that already found applications in other cognitive domains at the time externalized language emerged. In this chapter, I provide evidence from sign language and from animal cognition that the perception of a discrete phonological signal relies heavily on abilities humans share with our mammalian cousins. I build the case for this view with evidence from both humans and animals, discuss computational models of categorization that can build categories through feedback between perception and production, and provide a natural case study in phonological evolution provided by a young sign language. These arguments support the view that the building blocks of the phonological system – features and categories – were present prior to the emergence of externalized language as we know it.