Marc D. Hauser 
Evolution of Communication [PDF ebook] 

Bound to become a classic and to stimulate debate and research, The Evolution of Communication looks at species in their natural environments as a way to begin to understand what the real units of analysis of communicating systems are, using arguments about design and function to illuminate both the origin and subsequent evolution of each system. It lights the way for a research program that seriously addresses the problem of how communication systems, including language, have been designed over the course of evolution.