In my defense, I was thinking in terms of hard evidence of language use. Since auditory preservation of speech has only been possible withing the last century or two, what means written language. Last I read the
Oldest Writing sample that has been discovered is a paltry 5,500 years old.
There is speech that is not language. Several animals have a fairly large range of vocalization, and many more have a wider range than they use. Language users are not the only ones to have these sorts of structures. I believe I read an article about wolves and some sort of large ungulates(maybe deer or elk?) that also had analogous vocal structures one thought unique to language users.
Even then, it is not all that far of a cry... It's still within an order of magnitude of my assertion. And another order of magnitude beyond that we would have been guided solely by the voice of our blood.
As far as establishing a history... Right now, that would consist of far too much wild speculation... Canonically, Klingons, Terrans, Cardassians, Vulcans/Romulans and others are all from the same stock species the "Preservers" spread through-out the Galaxy. Perhaps that stock species had a language, perhaps it only had language potential.