TheSymbolicSpecies by Terrence W. Deacon
ISBN 0393038386 The co-evolution of language and the brain. A very intriguing book it presents some fairly radical ideas about how languages came to be and why HumanBeings are so unique in that they are the only species so far to develop SymbolicSystems? in the wild.
It's a fairly dense book that covers a lot of ground, analyses of academic linguistics, evolutionary biology, neuroanatomy, pedagogical theory and anthropological paleontology are used as building blocks of his argument.
The concept of languages as organisms in their own right is probably the most difficult to grasp and the easiest to misunderstand of the arguments presented in the book. It's one of those ones where you really have to get into it before you experience that AhHa moment, and only then can you really start to ask how it might be wrong or misleading.