What makes us human, I think, is an ability to ask questions, a consequence of our sophisticated spoken language.
We have language and they do not. Chimps communicate by embracing, patting, looking - all these things. And they have lots of sounds. But they cannot sit and discuss. They cannot teach about things that are not present, as far as we know.
I think we're still in a muddle with our language, because once you get words and a spoken language it gets harder to communicate.
