The author of How Language Began is Daniel L. Everett, the hero of what turned out to be the final book from the late Tom Wolfe, The Kingdom of Speech, which I read back in 2016. Everett's primary claim to fame is his demurral from the Noam Chomsky school of human language: that we have a "language organ" in our brains that provides us with the power to generate syntactical sentences.
Wait a minute, says Everett. His research into the language of the Pirahã, a primitive Amazonian tribe, didn't fit into the Chomskian paradigm at all. Language, according to Everett, isn't "built in", it's not in any sense a hardwired "instinct". (Thereby contradicting a Pun Salad fave, Steven Pinker.) Instead, it's an invention of the human mind, like (as I've said before) a pencil or Buick.
Everett contends that "we" have been conversing in at least rudimentary ways (but distinct from animal communication) since the days of Homo erectus. This involves, obviously, a lot of discussion/argument about what language, at root, actually is. But Everett's arguments are at least plausible to my untrained brain.
I didn't find the book uniformly interesting. Everett seems to belabor the obvious at certain points. His prose is occasionally clunky. (And the book doesn't seem well-edited. One symptom: a footnote on page 277 has a misplaced asterisk in the text, very confusing.)
And remember, this is a controversial topic, and we're only seeing Everett's side of the controversy here. Which is fine, but it just means that the interested lay reader (me) probably should remain skeptical of both sides until there's a scientific consensus.
But there's a lot of stuff I didn't know, or didn't adequately appreciate previously. One example: we know that we need big-enough brains to use language. But Everett notes that many other parts of the human organism are involved, all of which needed to be evolved "enough" to handle the desired communicative tasks. For example, we have a remarkably flexible sound-generation system in our mouths, throats, and lungs, something only a few other species boast. Not only can it make the necessary range of phonemes, but also construct widely various pitches and volumes. And it pairs up well with our sound-reception organs, which can detect the subtlest differences in incoming acoustic vibrations.
All thanks (allegedly) to the "dumb luck" of evolution. A lot of things had to go right in order for language to work; enough to make me seriously consider creationism again.