One very obvious difference between the vocalizations of all our ape cousins and humans is the presence of air sacs in all the apes. Air sacs are essentially large bags that attach to the throat and lie atop the upper chest. Apes use them to make great big sounds, noises that make them sound larger than they are, rather like putting a truck horn on a Volkswagen to command respect. Humans do not have air sacs. Dutch linguist Bart de Boer has looked into the question of whether the absence of air sacs in humans has something to do with the rise of language. If it does, we can date language to at least 800 thousand years ago he told the Evolang conference in Barcelona this evening (Friday, March 14, 2008).