WARNING: unfounded speculation about unverifiable things follows.
It occured to me today on the metro that it is rather wierd that human beings have a built-in language-learning window in which they are receptive to language acquisition, as opposed to just being born with a language, which would make life much easier. It is as if what was selected for was not language itself, but the ability to learn a language (if that makes sense).
Then it occured to me that it is not actually necessary to belong to a species that is so "linguistically primed" in order to acquire language, although it certainly helps (cf. Koko the gorilla).
Which makes me speculate, unverifiably, that perhaps language, or protolanguage, was actually an invention of just such nonlinguistic beings. Perhaps long ago some smart prehuman hominid realized that, "hey, if I and the others in my troops were to associate certain sounds with certain things and behaviors and events, that could come in handy while on the hunt and running from toothy things and so forth." This would then be passed down through the culture, or protoculture, of the prehuman hominids, just as Koko teaches her children signing (I think), despite them having no inherent linguistic aptitude.
Then it at least intuitively would make sense that what would be selected for would not be language (an artificial system) per se, but the ability to acquire it easily.
Does this make any sense?