God doesn't require it.
Those who insist that God requires it make God look very confused:
He calls married men to be priests in the Eastern Rite, but only single men in the Latin Rite.
Oh, and He calls some Protestant married men to the priesthood in the Latin Rite after they convert, but He doesn't call any Catholic married men to the priesthood in the Latin Rite.
Mandatory celibacy is a Church discipline and can be changed at any time.
Thanks. I'm a historian, so naturally look at things from that perspective. I'm also trying to delve more deeply in to my Catholic faith, so any and all info is helpful.
I hate to sound like Dan Brown, but there does seem to be an awful lot of anti-female bias historically in the Church (as elsewhere). How much of the Church's teachings (as the oldest Christian church) come from historical biases and cultural norms of previous eras versus actual scripture? That's rhetorical, not looking to put you on the spot!