One of the central topics in Tomasello's The Cultural Origins of Human Cognition is language -- how it evolved, how it develops ontogenetically, and how it enhances our cognitive abilities. But Tomasello discusses language at a fairly high level (e.g., syntax, semantics, and pragmatics). For spoken language to have evolved (biologically or culturally), several changes in the morphology of our vocal tracts had to take place. In addition, speech must be designed to take advantage of certain properties of our auditory systems, some of which may have evolved since the evolutionary lines of humans and other primates diverged. So, in order to really understand the language faculty, and how it evolved, you have to understand speech production and speech perception. With that in mind, here are two good papers on the internet.
The first is a book chapter titled "What Are the Uniquely Human Components of the Language Faculty?" by Marc Hauser and Tecumseh Fitch. Yes, that Hauser and Fitch. But this chapter isn't about the recursion hypothesis. It's a nice historical review of the speech production and perception literature. Unfortunately, since it's a book chapter, the scanned version doesn't include the references, but if they cite something that you think you'd like to read, and you can't find the full reference, let me know, and I will find it for you.
The second source, which is cited by Hauser and Fitch, is a Behavioral and Brain Sciences paper by Peter MacNeilage titled "The Frame/Content Theory of Evolution of Speech Production." It's mostly about speech production, as the title suggests, and contains a lot of great info on the physical aspects of speech, along with a theory about how these and neural organization influenced the evolution of language.