In my opinion, I think that we will still hold to idea that spoken language is only specific to humans. Although there are many animals can communicate with people by sign language like gorilla's case or parrot which can say some words because people repeat some words or some deeds through time the animals respond for what people want from them. According to the differences between Koko (gorilla) and human child there are four aspects : hierarchical structure, infinite creativity, expressing displaced concepts and being rule-governed. In really, the human child maybe uses sign language or repeats some words in beginning of her/his life, and the human child acquires a language very quickly in a short period because the human child's brain develops
