It's somewhat pathetic, but I realized only recently (few months ago) how many of my favorite movies are based on PKD's books. And I still didn't read any of them. As for Valis, I'm only familiar with Radio Free Albemuth. Not exactly a jewel of cinematography, but at least I know now what is Valis all about. So yeah, "the empire" is alive and kicking. How it ties to (development of) human psychology and manifested behaviors could be certainly a good topic in itself. Although, while "researching" this piece I came across a paper claiming that during the (min.) last 10k years our psyche/intelligence/etc. was essentially the same.

Anyway, as you have noticed, what I laid out is, indeed, a very condensed version of what (more or less) happened. Honestly, to fit roughly five millennia spanning through three continents (and few academic disciplines even though the bulk is good ol' archaeology) and still make a point within one blog entry proved rather challenging--heck, each paragraph could yield several books, but that's well beyond my attention span :D

Thanks for the tip on The Immortality Key. I briefly skimmed through the free previews--it very much reminds of some books about Cannabis (and entheogens in general) I read in the 90's. Sadly the previews had nothing on Gobekli Tepe. Now, that is a very interesting topic, especially considering that DNA of the folks who build it also allegedly points to the builders of Stonehenge (and if I'm correct, partly also the builders of rondels, "temporary megaliths" found in Central Europe).

Btw. you may check Graham Pemberton as he has some very intriguing ideas about psychedelic origins of Christianity, too.