Julian Jaynes (1920 - 1997), American psychologist, in his book 'The Origin of Consciousness in the Breakdown of the Bicameral Mind' argued that people up to 3000 years ago did not have the ability to introspect, or achieve subjective consciousness. According to Jaynes, ancient humans operated by means of pre-programmed instructions or schemas. Jaynes called these people bicameral humans. The left hemisphere in these people executed the voice command issued by the right hemisphere, usually hallucinated voices of chieftains or else. These voices provided the answers when a person was under severe stress, a situation which he could not resolve his problems. Of course, these bicameral-mind people were not necessarily barbarians. Some had a fully developed language, a key component for achieving consciousness. Consciousness, in Jaynes' definition, is a box of conceptual tools that is not 'included with the hardware'. It had to be invented. According to Jaynes, this consciousness is a 'process, not an immediate sensation'.
Roughly put, it seems Jaynes had consciously developed people in mind when he implied that bicameral-mind era had ended . He should have been around to see what sub-humans are doing in Middle and Near East. According to Jaynes, bicameral-minded people obeyed the command of a warlord, hallucinated, unquestionably. Now imagine when you have a sub-human packed with highly advanced explosive to be detonated soon, but all of sudden the bomber decides to give up blowing himself up. Now, modern medicine comes to the monitor's aid and feeds the bomber with enough methamphetamine drug to disable any changing of heart on the bomber's part.
However, the idea of hallucination is not implausible. Incidentally, there is a bird called African grey parrot. It is kept by humans as a companion pet. This bird can mimic human speech or any other sound or voice. Its brain is a very sensitive voice recorder. Some claim that the bird can memorize long passages. Besides, we all have the ability to memorize songs sang by a vocal singer. Some healthy people tell us that they hear a voice in their head, including tinnitus. Some people suffer from schizophrenia, experiencing hallucinations, called by Jaynes Vestiges of the bicameral mind.
Perhaps we need to add a layman's opinion to this hypothesis: Presently, the command voice has undergone modifications. Every morning in Middle East, even in Europe, one can hear a call for prayer. Men scurry to buildings for prayer. Don't suggest that an alarm clock can do the job. Anyway, it seems the former hallucinated command is now acting in a different way. Remember it is the command that must be obeyed regardless of your belief.