The Mithra Cult was a contender for state religion in the Roman Empire. On Dec 24th they would walk through the streets, singing "behold the virgin has given birth to a savior".
This over 100 years BC.
Read JG Frazer "The Golden Bough" on this. For some time it was in the balance whethter the Mithra Cult or Cult of the Christ would win. (See Acts to see how Romans were debating on it)
As a result of the Christians clever politicking and poisonings, the scales tipped in their favor.
Other wise we would be singing of the "Bull of God that taketh away the sin if the world."
What would we be singing if the Jews had been swineherds?
Has anybody ever visited the tiny Mithra Church near Hadrians wall in England?
HB