How do monkeys hear each other? Are there voices in their heads?

Pascal Belin of the University of Glasgow discusses the implications of 'A Voice Area in the Monkey Brain':

<em>The use of vocalizations, such as grunts, songs or barks, is extremely common throughout the animal kingdom. Nevertheless, humans are the only species in which these vocalizations have attained the sophistication and communicative effectiveness of speech. How did our ancestors become the only speaking animals, some tens of thousand years ago? Did this change happen abruptly, involving the sudden appearance of a new cerebral region or pattern of cerebral connections? Or did it happen through a more gradual evolutionary process, in which brain structures already present to some extent in other animals were put to a different and more complex use in the human brain?</em>

Full paper at <a href="http://science-community.sciam.com/blog-entry/Mind-Matters/Monkeys-Hear-Voices/5700000564" target="_blank">Scientific American </a>