The interaction between cognition and the environment may have shaped how human language developed over time. I consider the possibility that extended cognition contributed to the evolution of human language. While ‘internal cognition’ refers to intelligent processes occurring solely in the mind, ‘extended cognition’ refers to the coupling of internal cognition with external objects in the environment. I present a timeline describing major linguistic developments which extended cognition may have impacted: (1) internal cognition and early forms of communication, (2) evolution of protolanguage, (3) co-evolution of full human language and extended cognition, and (4) development of written language. I argue that language and extended cognition are both forms of external scaffolding, which are systems that reduce the burden placed on an organism when interacting with the environment. Moreover, I argue that certain language usages ought to be thought of as extended cognitive processes. I discuss and ultimately reject the notion that the presence of extended cognition contributed to the development of protolanguage. I argue that extended cognition arose after the development of protolanguage and co-evolved with full language. Finally, I argue that writing systems are a clear example of how certain uses of language can be considered extended cognitive processes.