I’d speculatively propose the reverse: that a change occurred that led to our suppressing these “voices” to our subconscious, where they are still present but s

I’d speculatively propose the reverse: that a change occurred that led to our suppressing these “voices” to our subconscious, where they are still present but suppressed below the threshold of conscious awareness. Interestingly, in parts of the world, these voices persist (eg Ethiopia where a high percentage of people report regularly hearing voices in their heads). Also interestingly, this book you mention was one of David Bowie’s favourites - yes, he of the multiple pop personas.