It's not about the brain, it's about the body. Right brain innate connection to ones own body and to the world. We know that there are nouns because the body senses objects. We know there are verbs because the body can make movements. We know there are adjectives because the objects differs. It's a very left brain dominated view that would even contemplate that a language system would evolve free of interaction with the world, only through dna construct some language organ.

And language is probably a product of singing. Checkout "The Master and His Emissary: The Divided Brain and the Making of the Western World". Singing is used to share feelings in larger groups then ordinary grooming permit. Language is a systematization of singing. That is why music evokes feeling response more readily then words in ordinary speech, speech evolved later.