Yesterday I posted [here] a description of Maggie Tallerman's retort [abstract here] to the thought-firsters' idea that language evolved as a means of improved thought by allowing concepts to combine; we only later developed a way to externalize the thought as speech or signing. In that post I presented Tallerman's argument that words and concepts are not interchangeable and that words alone have properties that allow meaningful combinations. They get those properties via common usage.
Today I want to look at her treatment of syntax. Basically, she makes the same point: the rules of syntax are formed via general usage, or to use the jargon: syntax comes through externalization.