The present article responds to commentaries from experts in anthropology, apraxia, archeology, linguistics, neuroanatomy, neuroimaging, neurophysiology, neuropsychology, primatology, sign language emergence and sign language neurolinguistics on the book How the brain got language: The mirror system hypothesis (Arbib 2012). The role of complex imitation is discussed, and the distinction between protolanguage and language is emphasized. Issues debated include the role of protosign in scaffolding protospeech, the interplay between biological evolution of the brain and cultural evolution of the social interactions within groups, the relations brain mechanisms for action and language, and the question of when language first emerged.

Arbib offers a coherent proposal of how the brain has evolved to become language-capable. Integral to the argument are mirror neurons, cells discovered in macaque brains with interesting firing patterns, and studies on gestural communication of great apes. Here, I first discuss some complexities of the recent mirror neuron literature, which suggest that ‘mirroring’ may be an ontogenetically acquired, not an evolved, feature of neurons. Second, it is now clear that chimpanzee vocal behaviour is strongly mediated by social variables, and that individuals can use vocalisations to persuade and inform others, facts that have implications for gestural theories of language evolution. I conclude with discussing research most needed for making progress in understanding how human language has evolved.

The short answer to the question of How the Brain Got Language is “through biological and cultural evolution.” The challenge is to be more specific. I use the term “the language-ready brain” to suggest that the brain of early Homo sapiens was adequate to support language but that it required tens of millennia for humans to be able to exploit these innate neural capabilities to develop, cumulatively, languages and the societies that made languages possible and necessary. The ability to surf the World Wide Web is a recent example of society's expanding ability to develop technologies and social structures which allow humans to exploit their neural capabilities in ways that were not part of the adaptive pressures for biological evolution.

The two-fold challenge of the book, then, is to understand (i) what are the mechanisms of the language-ready brain and what adaptive pressures evolved them biologically; and (ii) how did those mechanisms support the emergence of language as well as modern-day patterns of language change, acquisition and use, and the social interactions which support them?