The bicameral state of mind ?

In another post “bicameral mind” was referred to and since I only have a vague notion, thought I’d refresh my memory and enhance my limited understanding. I found this, which seems like as good source as there is on the subject.
http://www.julianjaynes.org/julian-jaynes-theory-overview.php

Jaynes's theory can be broken down into four independent hypotheses: *Consciousness — as he carefully defines it — is a learned process based on metaphorical language. *That preceding the development of consciousness there was a different mentality based on verbal hallucinations called the bicameral ('two-chambered') mind. *Dating the development of consciousness to around the end of the second millennium B.C. in Greece and Mesopotamia. The transition occurred at different times in other parts of the world. The neurological model for the bicameral mind. * * * Why Julian Jaynes's Theory is Important There are a number of reasons why Julian Jaynes's theory is very important to understand. These include: It provides a more accurate view of human history. Jaynes's definition and understanding of consciousness brings more clarity to the issue than other theorists. It explains a wide range of otherwise inexplicable phenomena (divination, idols, monumental mortuary architecture, hallucinations, imaginary companions, etc.) It explains the origin of religion. It provides a historical context for hearing voices, which is often comforting to those who have the experience. It provides a neurological model for hearing voices, which has now been verified in dozens of brain imaging studies, that could help lead to future treatments for those with persistent, obtrusive voices. * * * Understanding Jaynes's Theory There is no short cut to understanding Jaynes's theory. ...
No doubt. But you know the whole thing devolved into an interesting curiosity, rather than any path to understanding worth investing copious hours into - with this:
Jaynes asserts that consciousness did not arise far back in human evolution but is a learned process based on metaphorical language. ...
So human's are somehow qualitatively unique from the continuum of evolution??? Where is there any serious empirical evidence to support such a fundamental notion?