Julian Jaynes (Princeton psychologist/lecturer/scientist, died 1997) concluded from an extensive study of ancient texts (including the works of Homer, the Epic of Gilgamesh, and the Bible) that ancient man was not conscious the way modern man is.
Jaynes, in The Origin of Consciousness and the Breakdown of the Bicameral Mind posits that man wasn't conscious at all until about 3,000 years ago and that the development of human consciousness can be traced quite clearly in ancient literature/texts/codices. [Also see the Julian Jaynes Society site for more discussion of this matter].
Here's a review of Jaynes work (there are many others at the Jaynes Society site)...
"Neuroimaging techniques of today have illuminated and confirmed the importance of Jaynes' hypothesis." − Robert Olin, M.D., Ph.D., Professor Emeritus in Preventive Medicine [Karolinska Institute, Sweden], in Lancet.
“When Julian Jaynes . . . speculates that until late in the twentieth millennium B.C. men had no consciousness but were automatically obeying the voices of the gods, we are astounded but compelled to follow this remarkable thesis.” — John Updike — Review
20th millennium? 20,000 BC?