In 1976, psychologist and Princeton lecturer Julian Jaynes published The Origins of Consciousness in the Breakdown of the Bicameral Mind, a radical detailing of mankind's ascension to a state of true consciousness. According to Jaynes, humans only developed the ability to think for themselves, consider their actions, and stand aware of their own awareness about 3,000 years ago. Before then, they took orders from voices inside their heads, which they believed to be deities. The left hemisphere of the brain would shout "jump" and the right hemisphere would say "how high?"
Jaynes's major evidence for this separation is the stark contrast between Homer's Iliad, written by "non-conscious minds" and lacking in introspection of any kind, and the Odyssey, where characters reflect on their surroundings and act on their own volition. Jaynes believes that between the tellings of these two stories, Earth's sure-footed denizens realized the "words from the Gods" echoing through their minds were the product of their own instincts. As you may expect, reviews for The Origins of Consciousness in the Breakdown of the Bicameral Mind were glowing and vicious -- "the bicameral mind" theory had holes, but Jaynes's narrative thrust left a community thirsty for answers drunk on possibility. A little like Westworld, really.