My friend and erstwhile colleague Josh Birchall posted a link on Facebook to an interesting TED talk by Mark Pagel entitled How Language Transformed Humanity, on the development of language as a communicative tool and how it presented a huge evolutionary advantage over non-linguistic species. It isn't difficult to see how language, an infinitely productive system capable of expressing ideas that are not tied to a specific time and location, confers a greater benefit than other forms of communication. Language can be used to transfer abstract ideas and share a much wider range of information and technology compared to, say, the system of pheromones that ants use to communicate. It is for that reason that many archaeologists typically assume that the rise of abstract expression (viz., art) and the exponential proliferation of tool development coincides with the rise of language.
At any rate, it's an interesting talk, even if it's not perfect, and I think well worth watching.