A virgin birth is not a "sign"? Gee, how many virgins are there who ended up becoming supernaturally pregnant, with their hymens broken from the inside-out when the baby was born? To top it off, this "expert" can actually sit there and suggest "there never was a 'virgin' birth prophecy?
DRUM ROLL, please!
Isaiah 7:14 Therefore the Lord himself will give you a sign: The virgin will conceive and give birth to a son, and will call him Immanuel.
Immanuel means “God with us.”
Isaiah 9:6 For unto us a child is born, unto us a son is given, and the government will be upon His shoulders. And He will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.