Overview

Having considered the vocal tract, we now turn to another organ with a level of apparent specialisation for language, namely the human brain. There are two essential types of difference between the human brain and brains in other species: first, it is just vastly bigger than we would expect given human body size; and second, its internal structure and connectivity (as far as we can currently tell) are distinctive. In this chapter we shall provide a brief overview of the shape and function of the brain, and consider the evidence we have for linguistic specialisations and for brain evolution. As with the vocal tract, much of this evidence is indirect and interpretations vary; furthermore, much of the relevant neurolinguistic data is very new, so for the most part we shall be reviewing ongoing debates rather than coming to definite conclusions. In addition, we proposed right back in Chapter 1 that the human capacity for language cannot be understood as a single object of enquiry; rather, we have to engage with it on three levels at once if we hope to cast any light on how it emerged and how it works. Those three levels are the controlling genes; the physical or neurological structures they build in particular environments; and finally the phenotypic, surface systems or behaviours which these structures permit. It follows that evolved aspects of the human brain must have genetic underpinnings, and we turn to these in the next chapter.