To me there looks to be a very, very thin evidential basis for the "bi-cameral" revolution. Wafer thin. I don't accept Mr Jaynes as an authority on consciousness, despite his book. A global cultural explosion in material development doesn't equal the emergence of "that which is introspectable."
Imho, it's just Darwinian/New Age bunkum - part of the same categoric positive feedback loop that pervades practically all the sciences, but applied anthropologically (which imho again, is similar to 'derivatives' in economics - totally batshit freaking crazy, because for all the apparent 'credentials' it has frighteningly little relevance to anything resembling actual observations due to its fixation with minutae - Mr Jaynes' theory doesn't even have credentials).
It's also very polluting semantically - adding to the utter confusion re: consciousness.
My point is, that the phrase "that which is introspectable" begs the question, 'why do we know practically nothing about 'that which is introspectable', despite Mr Jaynes' book?
And how high is his theory on the scale of introspectability, from, say ...
1. Why do I suffer? or How can I be happy?
Does Mr Jaynes describe pranayama or yoga at all?
99.999+% of everything can't be that simple, can it?