I have read somewhere that the birth of Jesus is much easier to understand outside of the religious context.
For Jesus to have been considered human he would have needed complete human DNA. While Mary would have supplied the X chromosome, another human had to supply the essential Y chromosome
"The story of Virgin Birth was created to cover up the secret union of Mary and Joseph, which led to the conception of Jesus during her stay in the Monastery. This may have saved her life, since it was prohibited to marry while in the monastery, but led to the ignorant concept of "Jesus Son of God" by the people."
Instead of outright establishing the paternity of Jesus, the writers of the story took the mythological route prevalent at the time -like Son of Zeus and Virgin Birth.