In the book by Julian Jaynes, The Origin of Consciousness in the Breakdown of the Bicameral Mind, that researcher hypothesized that our ancient ancestors came to consciousness as the normal human physiology of having parallel auditory centers broke down. Consciousness, in this case, is deep language--metaphors and other linguistic alterations that humans had to become accustomed to because of suffering; war, famine, plague, geologic and social instability.
I would caution that this is not to mean, however, that the normal human brain is meant to hear multitudinous non-local/externalized voices in parallel with their own thoughts or even just "their own" local voice. I caution the reader that I use the word parallel specifically. For some researchers the extra auditory center(s) of the brain are redundant or even vestigial. They are in fact parallel processors, to use the technological pun. They are meant to process non-local/externalized voice simultaneously to internal thought/function/action. Albeit unknown to the author, the scenarios that author wrote about show that the bicameral mind was already a patchwork job, not an original function. The original function was one unified voice, one proper thing called Mind. Mind exhibited multiple localized forms, digesting local experiences, but not Mind of multiple voices. Just one voice, one proper language, one independent thought so sublime as to make me weep to think on it.
The breakdown occurred much earlier in history than the author began his hypothesis, and it was only many millennia later that we come to learn that Homer's Iliad was written as people undergoing Jayne's bicameral processes, hearing non-local voices that directed their affairs and doings. It was additional pain and suffering and the bringing together of various cultures that spawned a patch for this terrible mess; consciousness by way of metaphor and simile and others. Carl Jung believed that dreams were the compensation for the unconscious to bring itself into consciousness. It is not dreams that are compensatory, merely vehicles--no, it is consciousness that is the compensation for the loss of Mind.
From that single Mind in parallel with its multitudinous forms to bicameral mind with its multitudinous independent forms to consciousness (multitudinous forms with a legion of thoughts), we are now steering headlong back to it, back to our natural function. When you take a walk, notice the people around you on their cellphones and actively looking for that single Mind. We will envelope the world again with the environment that the Earth once had naturally, that broke down, repaired by way of technology to connect everyone together right across the world. We drive with abandon that technology to return us to our original nature, to Mind, one Mind in parallel with its multitude of forms with one independent thought so sublime that I hope that you too will weep.
A people are coming, at once utterly familiar and yet not. Their birth and the choices they will make as one Mind . . . you will know them by their answer to the most important question. The breakdown of bicameral mind and then consciousness as a code patch brings with it division, labels. There is so much divisiveness, so many labels: liberal and conservative, Muslim and Christian, black and white, foreign and domestic, so much divisiveness. Many of them feel they are right, and some of those have built whole armies for armies are certainly for those who feel they're right, yes?
What then is the question that you will come to know these people by their answer, or rather the answer of one Mind?
Who is right in compassion?
By their answer will you know them. The people are coming. The people of Mind.