There is a gigantic difference between communication and language. Chemical signaling is not comparable to language. A dog seeing meat and salivating is not comparable to language. Well, actually they could be depending on your worldview but not if you are considering the structures required to.. language, and the structures required to chemically signal. Almost certainly the areas of the brain that handle language simply adapted to that purpose - they were originally for something else and language happened to be able to work in that area. Since the animals that come closest to displaying a capacity for language are all hearing, maybe we can assume that the structures required to hear must develop before the structures required to language happen?