Interesting ideas on the spirals, though I favor the social and astronomical hypotheses over the more emotive ESP ones. I thought the spiral might be a symbol of growth, because it gets bigger if you draw it starting from the center -- growth of people and communities. No reason why that idea cannot be correlated with the effect of the sun. You could reverse-think it into death too, I guess.
Anyway, there is a kind of power in the spiral, and not of the ESP-sensed kind either. The spiralling vortexes of the eddies in a river (where Richard's idea of 3D from 2D might find some support, as you can see down into these mini whirlpools an inch or so), where many of these communities were situated, is an under-rated source of the philosophy. I've kayaked on my native Merrimack River and sailed my outrigger on the coast where topography sometimes combines with hydrology to suddenly spin the small craft around in a powerful eddy. I imagine the people seeing these things and experiencing them in their rafts, dugouts, and coracles (which would spin really well in an eddy) and working the shape into a philosophy.
Of course, this is all gobbledegook, as good or as bad as anyone else's, since we can't ever know. -- Wade