While it is accurate to say that there have always been people who were celibate, both within and without the Church, it was most decidedly NOT a Christian mandate in the New Testament for "priests" -- in fact, the First Century Church regarded themselves as "a nation of priests" and in the universal priesthood of the Believer. This concept of a clergy-laity distinction as viewed by the Roman Catholic Church evolved over centuries, until the time of Constantine (Fourth Century) it came to rule the Roman Catholic church and later the Western world. It was most certainly neither the prevailing view nor practice of the first two centuries after Christ.
Mandatory celibacy of Catholic priests is NOT 2,000 years old, as I have heard some talk show hosts say. (Since the Catholic Church is less than 1700 years old, it couldn't be!)
Those who maintain that "celibacy of Catholic priests is a 2,000 year rule," are displaying their ignorance. This doctrine, as a mandatory rule for RC priests, is precisely 882 years old.
This doctrine can be changed by another Council. (But it can't be changed by local or national political pressure.)
I quote from the Catholic encyclopedia:
First Lateran Council (1123)
The Council of 1123 is reckoned in the series of ecumenical councils. It had been convoked in December, 1122, immediately after the Concordat of Worms, which agreement between pope and emperor had caused general satisfaction in the Church. It put a stop to the arbitrary conferring of ecclesiastical benefices by laymen, reestablished freedom of episcopal and abbatial elections, separated spiritual from temporal affairs, and ratified the principle that spiritual authority can emanate only from the Church; lastly it tacitly abolished the exorbitant claim of the emperors to interfere in papal elections. So deep was the emotion caused by this concordat, the first ever signed, that in many documents of the time, the year 1122 is mentioned as the beginning of a new era. For its more solemn confirmation and in conformity with the earnest desire of the Archbishop of Mainz, Callistus II convoked a council to which all the archbishops and bishops of the West were invited. Three hundred bishops and more than six hundred abbots assembled at Rome in March, 1123; Callistus II presided in person. Both originals ( instrumenta) of the Concordat of Worms were read and ratified, and twenty-two disciplinary canons were promulgated, most of them reinforcements of previous conciliary decrees.
Canons 3 and 11 forbid priests, deacons, subdeacons, and monks to marry or to have concubines; it is also forbidden them to keep in their houses any women other than those sanctioned by the ancient canons. Marriages of clerics are null pleno jure, and those who have contracted them are subject to penance.
Canon 6: Nullity of the ordinations performed by the heresiarch Burdinus (Antipope Gregory VIII ) after his condemnation.
Canon 11: Safeguard for the families and possessions of crusaders.
Canon 14: Excommunication of laymen appropriating offerings made to the Church, and those who fortify churches as strongholds.
Canon 16: Against those who molest pilgrims on their way to Rome.
Canon 17: Abbots and religious are prohibited from admitting sinners to penance, visiting the sick, administering extreme unction, singing solemn and public Masses; they are obliged to obtain the holy chrism and holy oils from their respective bishops.