In reply to:

But on the other hand, once you admit that sign language is the same, is the mating dance of the blue-footed booby a form of language?

Language has certain features that the mating dance of the flat-footed booby probably does not have. For example, language can be used to talk about something that is not present. Do flat-footed boobies do their mating dance if no potential mate is present?

Bingley


Bingley