The Evolution Of Symbolic Language by Terrence Deacon and Ursula Goodenough. Deacon's The Symbolic Species: The Co-Evolution of Language and the Brain is a book I liked a great deal, though in hindsight I don't think I had the background to appreciate it in any depth (nor do I now).
Symbolic Species sounds like an interesting book worth checking out. However if you felt you didn't have the necessary background to really appreciate it, I'd be concerned about my own ability to do so. Exactly what background knowledge do you think would be useful in reading it?
Also, in my googling I found that John Hawks did a blog post about Deacon's ideas a few years ago; I found it useful as a quick summary. Deacon's upcoming book Mind from Matter also sounds interesting based on the title, but I couldn't find any real information about it online, at least in a quick search.
Deacon is what we should be talking about when we talk about evolutionary psychology.
Re Terry Deacon (et al), see:
Thanks to Charles Wolverton for the "On the Human" reference, which seems to be the longer original from which the NPR article was adapted, with a bit more detail. Another article I found interesting was an interview with Deacon that touches on a number of different topics around the evolution of language, including the differences between speech and writing in terms of their support in the brain.
Also, re my comment above on the paucity of information on Deacon's upcoming book Mind from Matter: That's apparently a new title. Deacon was previously planning to call the book Homunculus, which reminded me of Wallace Shawn's scene in Woody Allen's Manhattan. Thank goodness he changed his mind.
You should also check out the comments section of the "On the Human" reference provided by Charles Wolverton. It contains some fascinating insights from some of the leading thinkers in language evolution and associated disciplines, including: Mark Turner, Derek Bickerton, Salikoko Mufwene, Sue Savage-Rumbaugh and many others.
Having only had a cursory glance at the comments (some of which almost match the length of the initial article) I think Deacon's response aptly sums up the difficulties surrounding language evolution: "To approach this complex mystery with the respect it deserves, however, we must be prepared to give up on simple one trick accounts, innate mentalese, miraculous mutations, increase in general intelligence, and so forth, and embrace its complexity as a semiotic-biological-epigenetic-social phenomenon whose structural features reflect the convergent co-evolutionary interactions of all these levels of causal process."
That interview was especially useful for my purposes. Thanks a bunch.