From my point of view, you're the one putting forward an unclear statement. I understand what the author is saying clearly ("only humans developed language"), regardless of whether I agree or not. I can't guess what you're referring to, though. Are you referring to non-human animals, to the different species of human in prehistory, or both? What kind of communication are you considering to be language? I may even agree with you, but your tone seems unnecessarily hostile.
I think a "hostile tone" is appropriate to muster in response to Nautil-dot-us, a science-y woo populist publication.
As far as the claims, humans keep redefining what "language" means to only include their own species. See also: intelligence. And "appearing only once" is similarly redefined as needed.
If they make their own tautologies because they're defining terms, they might be spinning beautiful poetry, but not meaningful truth.
I doubt the poetry, too, but that's a longer conversation.
I’m referring to the fact that non-human animals are widely known to have language, and that the only way the quote could make sense is some specialized meaning of language that wasn’t specified.
"non-human animals are widely known to have language". I remember reading years ago about Koko the gorilla being taught sign language, but that Koko was incapable of seeing the sign for 'fire' without having a fear response. McCarthy didn't spell it out in the article more than to say:
"The simple understanding that one thing can be another thing is at the root of all things of our doing. From using colored pebbles for the trading of goats to art and language and on to using symbolic marks to represent pieces of the world too small to see."
I infer from this that a more sophisticated (or, in your words, specialized) definition of language that is of interest to McCarthy includes abstraction. I can talk about fire without arousing fear in a fellow human because they understand I'm not announcing the immediate presence of fire, I'm talking about it abstractly. As far as I know, no non-human animals are known to have the ability.
Soup Emporium on YouTube has a fairly detailed and compelling (at least to me as a lay person) video about Koko and whether she could truly speak. He argues that, while she could perform signs correctly, there's little evidence that she understood them in the context of actual language, and rather saw them as tools associated with certain outcomes. For example, signing "food" when you're hungry is a form of communication, but so is a cat meowing loudly near its food bowl. It is a large leap to then claim that this communication approximates language simply because it uses the same tools.
Huh? This is either plainly false or using some unconventional jargon that's useless for an outside reader.