This Doctrine is very Old goes back to the beginning of Christianity. It's was never put down as official dogma because it was rarely ever disputted. When the Pope had established this Dogma it was either to silence some heresies or it was that the Pope decided there was enough research done and decided to declare it.
The feast of the Immaculate Conception, celebrated on December 8, was established as a universal feast in 1476 by Pope Sixtus IV.
The Immaculate Conception was solemnly defined as a dogma by Pope Pius IX in his constitution Ineffabilis Deus, on December 8, 1854.
So almost 400 years after the declaration of the Feast did the dogma finaly get defined.
But it goes back further then that....
Eadmer, or Edmer (10601124), was an English historian, theologian, and ecclesiastic. Eadmer's theological works include the "De conceptione Sanctae Mariae", a tract of much importance for the development of the doctrine of the Immaculate Conception
It goes all the way back to the Early Church Fathers after him. As far back as 150 A.D.
Justin Martyr [100-165 A.D.] Dialogue with Trypho Chapters 48
[Jesus] became man by the Virgin so that the course which was taken by disobedience in the beginning through the agency of the serpent might be also the very course by which it would be put down. Eve, a virgin and undefiled, conceivedthe word of the serpent and bore disobedience and death.But the Virgin Mary received faith and joy when the angel Gabriel announced to her the glad tidings that the Spirit of the Lord would come upon her and the power of the Most High would overshadow her, for which reason the Holy Onebeing born of her is the Son of God. And she replied 'Be it done unto me according to your word' [Luke 1:38](Dialogue with Trypho the Jew 100 [A.D. 155])
Yes this letter was written back in 155 A.D. Here Justin Martyr compairs Mary to Eve. Mary by many of the Early Church fathers viewed her as the new Eve. They Compare Mary to Eve before Eve was lead into sin.
Irenaeus of Lyons [120-180 AD] Adversus Haereses Book III
"Consequently, then, Mary the Virgin is found to be obedient,saying, 'Behold, O Lord, your handmaid; be it done to me according to your word.' Eve, however, was disobedient, and, when yet a virgin, she did not obey. Just as she, who wasthen still a virgin although she had Adam for a husband-for in paradise they were both naked but were not ashamed; for,having been created only a short time, they had no understanding of the procreation of children, and it was necessary that they first come to maturity before beginning to multiply; having become disobedient, was made the cause of death for herself and for the whole human race; so also Mary, betrothed to a man but never the less still a virgin, being obedient, was made the cause of salvation for herself and for the whole human race. . . . Thus, the knot of Eve's disobedience was loosed by the
obedience of Mary. What the virgin Eve had bound in unbelief, the Virgin Mary loosed through faith" (Against Heresies 3:22:24 [A.D. 189])
In 189 A.D. we have Irenaeus of Lyons going into further detail on Mary and her obedience to the Lord again compairing her with Eve.
St. Ambrose did some studies on De institutione virginis et sanctae Mariae virginitate perpetua ad Eusebium (On the Birth of the Virgin and the Perpetual Virginity of Mary)
When it comes down to Dogma and Doctrine The church compares every new idea or reworked ideas to scripture and tradition and then after enough research is done on a topic it is deemed as a heresy or dogma. The church has almost 2000 years of history of great theologians that dedicated their entire lives to studing every aspect of the Christian Faith. There is no need to rediscover the wheel only to futher define the truth as it is revealed to us through out the ages.
