I realize that it has been claimed on this list that these features are unique to human language. Since cetaceans use echolocation to explore their surroundings, as well as passive hearing, it seems to me that their dominant sense perceptions are probably aural. This may not appear to be relevant to possible differences in the structure of communication, because human language manifests primarily as sound.
Slugs are stupid.
Dolphins are not stupid. That makes me curious. So I don't think it's anti-scientific to wonder about these issues, not at all. The assertion may turn out to be wrong, like many assertions based on informal observation, but it is by no means a priori. Contrast this with the position taken by Savage-Rumbaugh and Lewin in the book on Kanzi whose NY Times review provoked Schaufele's message.