I don't know that I can ably add to other aspects of the discussions of Jaynes' work on the bicameral mind, but I may have a few thoughts to offer here, or at least, some online resources for consideration.
An anthropologist has an online manuscript, that appears to be a work in progress, posted here: http://cc.usu.edu/~fath6/contents-bible.htm
His research is valid, although I don't agree with all of his conclusions. He seems to jump from a secular humanist POV to a Western religious POV ...and back again quite regularly.
The first few chapters are relevant, and explore the origins of religion in the Middle East in an accurate and succinct fashion. It is not an extensive treatise on the topic, but it does touch on many of the major 'players' and of their origins, 'godheadly' speaking...
Another topic that may also be of relevance, although I have not explored it with any in depth research, has to do with certain aspects of The Plasma Universe Theory and The Electric Universe Theory, wherein The Big Bang Theory is rather vigorously refuted. Some components of the Exploded Planet Hypothesis fit within those frameworks as well. (That's a lot of theories, isn't it...)
Anyway, not knowing any better, I can't help but think of the brain's electrical activity in view of those theories. Catastrophism in ancient times, and even pre-historical times, is well attested to world-wide by archaeology, papyri, clay tablets, murals, motifs, and other texts and contexts. If an electrical/plasma solar-wide catastrophe occurred about the time of the beginning's of Jayne's proposed end of the Bi-Cameral Mind, and the earth was in the line of fire, so to speak, there might be a bit of an explanation for the 'gods' to stop 'speaking' to every individual, or for individuals to be able to work together in a pre-Tower of Babel, one-language fashion. Other cultures describe a similar occurrence as that of Babel as occurring in a similar time frame. With one huge cosmic electrical discharge, part of our minds may have been electrically shorted, and the "charge" reversed, or the mechanism damaged in some fashion.
Just ...an undeveloped thought.http://www.varchive.org/itb/http://www.catastrophism.com/cdrom/pubs ... ls/pensee/http://www.grazian-archive.com/quantavo ... t_here.htmhttp://www.metaresearch.org/http://www.plasmacosmology.net/spec.htmlhttp://public.lanl.gov/alp/plasma/universe.htmlhttp://thunderboltsfilm.com/PAGES/links.htmlhttp://www.electric-universe.info/
"When a well-packaged web of lies has been sold gradually to the masses over generations, the truth will seem utterly preposterous and its speaker a raving lunatic."
- Dresden James