For the record, I am NOT Catholic, and as such, have no history or background for this post.
I was listening to a news program Monday (radio) and they were discussing the issue, because there is also a criminal case currently going on in the Bay Area where a priest (former) is on trial for allegedly raping several young women (14 years old) years ago.
At any rate, a caller (Catholic) stated that the celibacy rule is NOT original to the Church's formation. She stated that originally [I don't recall the date, but it was EARLY in the Church] clergy WERE allowed to marry, but that the Church [date forgotten by me] in Rome decided that because of ownership issues, Clergy were to be prohibited from marrying. Apparently (according to the caller), the Church felt it would be difficult to separate and define who owned what if there was marriage, whereas it would otherwise all go to the Church upon the Priest's death.
I'm sure that I've gotten everything all mixed up here, because frankly, I was only listening with three-fourths of an ear, but the net is that the requirement of celibacy may not be an original requirement for the Clergy, as say, belief in Christ would be. Maybe someone knows more/valid information about this part of the story?