Ying and Yang? Duality of humans, ergo man/woman? Or, has there been an advanced civilization in the distant past that somehow was completely wiped off the face of the Earth, yet some hints of their existence still are around to be found by people who believe in their being here. The pillars underneath the Egyptian Pyramids come to mind, yet somehow that isn't advanced enough for me to believe they could move megaliths. Would outer space aliens have come here and left humanoids? Why then haven't the humanoids have left graffiti showing the aliens space craft? Only Ying and Yang spirals. Hmmmm