What can other great apes really do?

[Hatshepsut]

I recall Clever Hans, an equine mathematician...

I wouldn't underestimate horses, either. They're very sensitive to tiny signals and have long memories. They can recognize human beings and other horses as individuals and develop bonding relationships with them. It takes a lot of intelligence just to do that.

Really we're putting apes in what is for them a highly artificial situation when we try to get them to use language. They're on our turf now and can't be expected to show a knack for it, and they don't. Many apes flunked out of language school altogether. A 3-year old human can beat the best ape scholar's lifetime achievements when it comes to language. Human cerebral cortices are three times as large as those of apes, with at least 50K years of evolutionary history in modern language-using environments.

But apes have shown themselves smart enough to "figure out" the rudiments of human language and apply this knowledge to novel problems. Some of the experiments you were asking about have in fact been done: Apes "talking" to other apes without a human moderator's assistance, for example. Operant conditioning, as used with Clever Hans, is of course found in rock pigeons, horses, and humans, the difference being the complexity of the stimulus and its target response. Young children won't learn language unless they are exposed to setting which rewards it.

I don't think apes use language in the wild. They don't normally share food, either, though there's an important exception where chimps will share the meat from a monkey one of them has hunted. Iroscato's photo shows that apes, along with elephants, have a peculiar awareness of death. They wouldn't gather around the fence like that if the people were just taking one of them out of the enclosure for a ride.

Christine Kenneally explores some of this in The First Word: The Search for the Origins of Language (Penguin, 2007).