So the Biblical scholars mis-translated the Hebrew word for "young woman" into the Greek word for "virgin," which was a pretty easy mistake to make, since there is only a subtle difference in the spelling. But back then it was the "virgin" that caught people's attention. It's not every day a virgin conceives and bears a son. So you keep that for a couple of hundred years, and the next thing you know, you have the Holy Catholic church.

http://www.imdb.com/title/tt0208092/