Apes could talk, so why don't they?

... if there is an elaborate code of chimpanzee communication, their human cousins have not yet cracked it. Chimps make a food call that seems to have a lot of variation, perhaps depending on the perceived quality of the food. How many different meanings can the call assume? “You would need the animals themselves to decide how many meaningful calls they can discriminate,” Dr. Zuberbühler said. Such a project, he estimates, could take a lifetime of research.Monkeys and apes possess many of the faculties that underlie language. They hear and interpret sequences of sounds much like people do. They have good control over their vocal tract and could produce much the same range of sounds as humans. But they cannot bring it all together.

This is particularly surprising because language is so useful to a social species. Once the infrastructure of language is in place, as is almost the case with monkeys and apes, the faculty might be expected to develop very quickly by evolutionary standards. Yet monkeys have been around for 30 million years without saying a single sentence. Chimps, too, have nothing resembling language, though they shared a common ancestor with humans just five million years ago. What is it that has kept all other primates locked in the prison of their own thoughts?

Drs. Seyfarth and Cheney believe that one reason may be that they lack a “theory of mind”; the recognition that others have thoughts. Since a baboon does not know or worry about what another baboon knows, it has no urge to share its knowledge. Dr. Zuberbühler stresses an intention to communicate as the missing factor. Children from the youngest ages have a great desire to share information with others, even though they gain no immediate benefit in doing so. Not so with other primates. ... - NYTimes