If you are intersted in that sort of thing, paul devereux's wonderful 'a prehistory of psychedelia' contains some very interesting speculations on the conections between neolithic pottery, psychoactive drug use, rock art and megalithic culture - particularly in the case of breton passage graves.
Also of interest, is the american psychologist Julian Jaynes' theory regarding auditory hallucination, the 'bicameral' mind and its transformation during neolithic times. The speculation that movement from a 'smoking culture' to a 'drinking culture' mirrored or was responsible for some of the major shifts in ritual building and demolition is fascinating.
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