Spike and Tim,
I think it may be useful to differentiate between two concepts here. One being the ecstatic, spiritual experience (or perception), and the other being the meme or meme complex of God(s) and/or religion. The two are often linked, indeed I believe often people who have had a spiritual feeling seek religious memes, rightly or wrongly, to explain their experience and fit it into their overall model of the world. However, they are not the same, in my opinion. I would say that the memetic concepts of Religion and God are likely learned/environmentally derived. I am not certain of the etiology of the spiritual experience, however it would not be surprising for me if it were at least in part genetic. One way to look to see if there seems to be a genetic basis for spirituality would be to start with pedigree studies. For example, in my family, my mother and myself seem to have strong spiritual experiences, whereas my father, brother, and my sister do not. My mother and sister, however, have the most strongly entrenched memes about God, with my father having almost none, and my brother and myself somewhere in between. My fiance does not have any spiritual experiences, though she has tried many times to. Her mother, on the other hand, has had strong spiritual feelings. Her father and sister seem more like my fiance in this regard. I think that having feelings of spirituality is a strong predisposer to developing "Religious" memes, but that it is not absolute in either direction. I too would be interested in seeing if this is genetically based.