Language: From how-possibly to how-probably?

Language confronts the human evolution community with an inescapable challenge. The challenge is inescapable because language is both a unique feature of human social life- no other animal has anything like it-and a fundamental feature of human life and cognition. Only the expressive power of human language makes possible our forms of social life. For that form of life is dependent on a large reservoir of collectively built, publically available information; it is dependent on complex, error-intolerant coordination, often over considerable time depth and spatial extent; it is infused with norms and narratives about who we are, and who we are not; it depends not just on social learning but active teaching. Precursors of these aspects of social life, very likely, antedated the emergence of language as we now know it. But coordination over time and space with differentiation of roles; the narratives of social identity; the kinship systems that structure social interaction in many communities; all this and more depends on language. Likewise, our ability to use this system, and live in the social world that it makes possible, has shaped our mind (see, for example, Dennett 1991; Tomasello 2014). So an evolutionary theory of human nature-of how we became such an unusual great ape-must include an account of language and its emergence.