I find it difficult to believe that we can simply assume physical humans didn't develop language until ~60,000 years ago or whatever, even though we existed in a biologically identical/near-identical fashion for, say, at least 140,000 years at that point.
I mean, what can possibly fuel such a hypothesis? Really?
There is really no evidence, whatsoever, of what life was like for such humans for the first roughly three quarters of our biological existence. Oh, and we may have been around for longer, there's just no direct evidence of it, right?
It seems HIGHLY speculative, to say the least.
We know that we coexisted with other intelligent primates up until, what, ten or fifteen thousand years ago? Possibly even less? We know that those other subspecies had language, and art, right? But our own species were, what exactly, grunting at one another until... Something magical happened?
It seems more likely to me (yes, pure speculation) that we began to form language well BEFORE becoming the biological species we exist as today.