Of course my information goes back 5 or 6 years, and these timelines get changed all the time. But here is mu current understanding and I welcom corrections.
Biologically modern humans go back 100-150K. For the first 50-100K, however, that development left little evidence in the archaeological recored (tools, etc.) Human culture remained pretty much in the continuum of the preceding million years or so. Then about 40K ago radical changes in the record appear - including, above all, the first evidence of consciously symbolic activity. (Sculpture, bodily decoration, cave painttings, etc.). Something had happened, and whatever that was, it was a CULTURAL, not a BIOLOGICAL, change. The hypothesis of Tattersall and others are that this event was the invention and rapid spreading of language.
But there is _no_ record, and in the nature of things cannot be any record, of the CAUSES of that origin. That it was a slow piece by piece development (as in the dogmatic Darwinism of mid-20th century) is really hard to believe. Neuroscience, linguistics, genetics, etc. may or may no sometday identify the neurological foundations of language ability. Whether that knowledge, if ever acquired, would be relevant to the "origins" or "evolution" of language I do not know.
Carrol