Apostolic Origins of Priestly Celibacy?

The Roman Catholic church requires celibacy of all its priests. They maintain that the celibacy requirement is essentially of apostolic origin and that it was therefore binding on priests from early church history. If this claim of an apostolic origin for the Roman Catholic celibacy requirement can be refuted, celibacy is rendered without adequate foundation. The question of whether or not the Roman Catholic church will change the requirement of celibacy is secondary to the issue of whether or not there exists an adequate theological and historical basis for such a requirement.