Until someone with abstract reasoning skills and the ability to manipulate symbols ends up gathering wealth, settling disputes, averting war, all in such a way that his/her progeny and the progeny of their near relatives survive long enough to reproduce and more of the babies survive because they have a stockpile of grain and a stable system for distributing it and resolving disputes and safety from greedy neighbors due to their bartering skills, and safety from predators due to their own cunning and ability to abstract and predict the raiding patterns of both wild predators and crazy neighbors, thus preparing for or averting deadly raids, and more of them survive and have kids who survive to have kids and the village gets bigger and more of the genes get passed to the next generation and more of the newborns survive to reproductive age and then...
If I'm not mistaken, I think the human female has a much better developed mental capacity for conversation. Case in point, guys generally don't like to sit around complain. I prefer to solve problems, not complain about them. I've known gals who appeared to me to be seemingly content to complain to each other, rather than solve a problem. I know I'm not alone in this observation.
Now this is preferences, there are always exceptions, but generally speaking I would say this is true in my experience.
There must be some direct psychological connection between vocal communication and that door into rational thought. Words have meanings, have always had meanings, even before writing. A screech conveys a far different message than a coo does.
Another anomaly with human evolution is the larynx, which made speech as we know it even possible. I never heard a good scientific explanation for that one, either. I seem to recall the consensus some years back was that Neandertal had a larynx that was midway between human and "ape," that limited their vocal range, I seem to recall that idea was challenged but I never heard the outcome and haven't pursued it.
Humans undoubted spoke before writing, but I don't see how the vocabulary could be extensive. When did "we" begin telling stories or transmitting family histories? And I mentioned some time in the past the role of deceptive speech, lying, deliberately and with intent...when did humans gain this "art?"