"You have gestures"

Christine Kenneally on a study by Tomasello that aimed to determine differences between how humans and other primates use gestures and language:

The answer, he believes, is that humans are particularly cooperative in the way they communicate....In many theories of evolution, human altruism is treated as an anomaly. But Tomasello thinks of it as an evolutionary strategy that has served us incredibly well.
...
Tomasello and his colleagues' gesture work demonstrates both a continuum that connects human and ape communication and signficant differences between them. In our evolutionary history some individuals must have been born with a greater inclination and ability to collaborate than our common ancestor with chimpanzees. These individuals were more successful and bred more offspring with those characteristics, Tomasello said. What we have evolved into now is a species for whom an experience means little if it's not shared. Chimpanzees took a different path. In their communication, there is never just plain showing, where the goal is simply to share attention. While they do share and collaborate and understand different kinds of intentions, they dont have communicative intentions.
...
Tomasello's conclusions resonate deeply with observations made by Sue Savage-Rumbaugh...[who] worked with two apes called Sherman and Austin. The apes successfully acquired many signs and used them effectively. There didn't seem to be anything odd about their language use until one day they were asked to talk to each other. What resulted was a sign-shouting match; neither ape was willing to listen. Language, worte Savage-Rumbaugh, 'coordinates behaviors between individuals by a complex process of exchanging behaviors that are punctuated by speech.'

At its most fundamental, language is an act of shared attention, and without the fundamentally human willingness to listen to what another person is saying, language would not work. Symbols like words, said Tomasello, are devices that coordinate attention, just as pointing does. They presuppose a general give-and-take that chimpanzees don't seem to have. For this reason, Tomasello explained, "asking why only humans use language is like asking why only humans build skyscrapers, when the fact is that only humans, among primates, build freestanding shelters at all...At our current level of understanding, asking why apes do not have language may not be our most productive question. A much more productive question, and one that can currently lead us to much more interesting lines of empirical research, is asking why apes do not even point."

[from The First Word - The Search for the Origins of Language by Christine Kenneally - the passage above is probably my favorite fascinating tidbit in a book that's full of fascinating tidbits.]