Brain and language, warrants and claims: Toward a coevolution of language theories

This study examines theories of language and brain development as articulated by Terence Deacon in his book The Symbolic Species: The Coevolution of Language and the Brain. Historically, evolutionary explanations of language have been simplistic and have ignored how learning and creativity function in the development of language. Behavioral flexibility is the foundation upon which Deacon builds his argument for the evolution of language and the human brain, and also provides the means for this study to link Deacon's work to language learning theories in rhetoric and composition. Deacon's theories of language evolution, linked with language and learning theory suggests that language flexibility (learning and creativity) plays an integral part in both language and cognitive development. This bridge between Deacon's work and rhetoric and composition studies is built through a rhetorical analysis of Deacon's argument using Stephen Toulmin's model of argument to analyze the three primary warrants that support Deacon's central claim. The study then links the implications of this rhetorical analysis to questions about how the nature of language is viewed in rhetoric and composition studies---how it works, and why and how it evolved---to a wider context, that of language and learning in the disciplines.