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.
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.