How old is paganism?
Paganism is as old as the Civilization of Humankind. Pagan beliefs started when people started thinking about the natural phenomenon, Moon, phases, Season changes, Rain and Thundering, Tree growth, Harvesting and the Breeding of Prey animal, Maintaining Livestock etc.
Paganism is the original spiritualism, dating back past the civilization of humankind and originating at the point where we (as a species) became self aware. The first creature to raise its head and look at the stars with fear and wonder harboured the seeds of paganism in its breast.