The article's definition of consciousness is precise, but it's not what people are referring to in most cases where the word "consciousness" is used. Of course, a word can have multiple definitions. But colloquially, when people say consciousness, we usually mean the thing that goes away when we sleep or are anesthetized. I don't think there's a much better way to define that. The contrast between the wakeful and non-wakeful state as oneself experiences from the inside is precisely what defines consciousness in the colloquial sense. It seems to be a self-defining concept because I can't even define what "experiences" means without thinking about the wakeful/non-wakeful contrast phenomena that is consciousness, and "experiences" was supposed to be a part of the definition of "consciousness" one sentence ago.

Isn't this a testable hypothesis? If consciousness spread virally and isn't a natural outgrowth of the physical structure of the brain, then presumably isolated indigenous tribes would still have pre-consciousness mental processes, and that should be detectable somehow.

The being said, I'm reading "Proto" By Laura Spinney, and the thing that strikes me is how recently the world's major languages developed. Everyone assumes we had language fifty thousand years ago, but the actual language families we know about all seem to trace to no more than about 10,000 BCE, and maybe a lot younger than that. The odds of Proto-Indo-European being traceable to a single tribe in the Black Sea region circa 4500 BCE seem really low to me, but that's what seems to have happened.

I think this was also one of the inspirations for Neal Stephenson's "Snow Crash", which also deals with (among other things) the nature of consciousness and religion in the human mind.

And yet anendophasia is a thing. Some people think without an inner monologue, without words[^0]. And they seem to do so quite well and quite successfully.

[0]: https://johnrmiles.com/life-without-an-inner-monologue/

I find the description of consciousness in this article very narrow (Only arising post language). Post language consciousness is a particular type of consciousness, and the same can be said of post DMT consciousness (Which is sometimes without language).