Poetry begins as the divine speech of the bicameral mind. Then, as the bicameral mind breaks down, there remain prophets… others become specialized into poets, relating from the gods statements about the past.
Jaynes argues that rhapsodic poetic utterance originated as literal bicameral voice-hallucination, and its subsequent transformation into conscious craft traces the progressive silencing of that divine dictation.
, The Origin of Consciousness in the Breakdown of the Bicameral Mind, 1976thesis