The first lines of the Website you linked to reads:
"Let our Christian readers bear in mind that the worship of the virgin and her child was common in the East, ages before the generally received account of Christ's appearance in the flesh…"
This research tells me that many ancient religions model themselves on the archetypal Jesus, out of whose mouth our creation came into being...
"In the beginning was the Word, and the Word was with God, and the Word was God. He was with God in the beginning. Through him all things were made; without him nothing was made that has been made. In him was life, and that life was the light of men. The light shines in the darkness, but the darkness has not understood it." - John 1
9 "As the heavens are higher than the earth,
so are my ways higher than your ways
and my thoughts than your thoughts.
10 As the rain and the snow
come down from heaven,
and do not return to it
without watering the earth
and making it bud and flourish,
so that it yields seed for the sower and bread for the eater,
11 so is my word that goes out from my mouth:
It will not return to me empty,
but will accomplish what I desire
and achieve the purpose for which I sent it.
Spiritual traditions develop when spiritually aware people grasp some aspect they see in the spirit and translate it into symbols, words and systems, etc. Some of these may be accurate, some may not, some may even be dangerous for the unprepared.
Christians believe Jesus was indeed the word of God, the logos incarnate and everything issued out of him from the begining of time, then why should it be a surprise that echos of him and his incarnation into flesh appear all over the place, before his very birth? Only a limited temporal outlook, or a reductionist scientific/aetheistic viewpoint, should discount the possibility that in the most important aspects, these similarities that exist elsewhere are reflections of Jesus and not vice-versa, whenever they happened.