Yeah...because everything Roman Catholicism believes was so clear in the 1st century. My comments in []
This doctrine underwent a period of discussion until the late fourth century when general consensus emerged.
[So the doctrine was not received by the entire early church.]
The earliest witness to the perpetual virginity of Mary seems to appear in the apocryphal Protogospel of James (circa 150). [A book that was NOT received by the early NT church as being part of the canon. If this book is true, then Rome should have added it to its canon at Trent in the 1500s....that it did not is telling]
Tertullian (d, circa 220) denied the virginity of Mary after Jesus' birth. Origen (d 254), by contrast, taught Mary's perpetual virginity. In the East, St. Athanasius strongly defended Mary's virginity after the birth of Jesus. Shortly after, St.Basil the Great (d, circa 380) accepted Mary's perpetual virginity and claimed that it reflected the general sense of believers, though he did not consider it to be a dogma.
[Contrary to what Roman Catholics often suggest, there were many people in the early centuries of Christianity who rejected the doctrine of the perpetual virginity of Mary. Though the doctrine was popular among the later church fathers, there was opposition to it even in those later centuries. The church father Basil commented that the view that Mary had other children after Jesus "was widely held and, though not accepted by himself, was not incompatible with orthodoxy" (J.N.D. Kelly, Early Christian Doctrines [San Francisco, California: HarperCollins Publishers, 1978], p. 495).]
Around the same time in the West, Jovinian and Helvidius denied the perpetual virginity while Ambrose (d. 397), Jerome (d. 420) and Augustine (d. 430) staunchly defended it. After this time, monasticism spread widely and the value of consecrated virginity became better known and widely accepted. General agreement and clear teaching on the perpetual virginity of Mary seem to have followed. [Like so many things with Rome....give it enough time and it will happen]
The official acts of the Fifth Ecumenical Council held at Constantinople in 553 refer to Mary as aeiparthenos (i.e. ever-virgin). For example, an anathema against the 'three chapters' condemns those who deny:
that nativity of these latter days when the Word of God came down from the heavens and was made flesh of holy and glorious Mary, mother of God and ever-virgin, and was born from her ... These statements were not made in reference to a direct discussion of Mary's virginity. Hence, some argue that this statement was not a dogmatic definition, even though it was issued within a definitory document. For Catholics, such definitions may be made by the Episcopal college, in communion with its President, the Bishop of Rome, or by the Pope in virtue of his Presidency over the entire Episcopal college. Such definitions must be derived, at least implicitly, from the revelation closed at the death of the Apostles.
Though not an Ecumenical Council, the Lateran Council of 649 convened by Pope Martin I also issued an important statement affirming Mary's lifelong virginity:
If anyone does not, according to the Holy Fathers, confess truly and properly that holy Mary, ever virgin and immaculate, is Mother of God, since in this latter age she conceived in true reality without human seed from the Holy Spirit, God the Word Himself, who before the ages was born of God the Father, and gave birth to Him without corruption, her virginity remaining equally inviolate after the birth, let him be condemned.
[Now we are 500+ years removed from the Apostles.]
After Constantinople II the title was universally accepted by the Church. Though already present in certain liturgical contexts, references to Mary's perpetual virginity were then propagated universally in the liturgical life of the Church. Hence, questioning the dogma's status as a 'definition' does not appear to be constructive. Note that some teachings which belong to the deposit of faith may not have been confirmed by a formal dogmatic definition (e.g. immortality of the soul?). This is often the case with teachings which have never been seriously contested.https://udayton.edu/imri/mary/p/perpetual-virginity-dogmatic-status-and-meaning.php
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St Thomas Aquinas, Summa Theologica, III.28.3 (13th century):
“Without any hesitation we must abhor the error of Helvidius, who dared to assert that Christ’s Mother, after His Birth, was carnally known by Joseph, and bore other children.
For, in the first place, this is derogatory to Christ’s perfection: for as He is in His Godhead the Only-Begotten of the Father, being thus His Son in every respect perfect, so it was becoming that He should be the Only-begotten son of His Mother, as being her perfect offspring.
“Secondly, this error is an insult to the Holy Ghost, whose “shrine” was the virginal womb, wherein He had formed the flesh of Christ: wherefore it was unbecoming that it should be desecrated by intercourse with man.
“Thirdly, this is derogatory to the dignity and holiness of God’s Mother: for thus she would seem to be most ungrateful, were she not content with such a Son; and were she, of her own accord, by carnal intercourse to forfeit that virginity which had been miraculously preserved in her.
“Fourthly, it would be tantamount to an imputation of extreme presumption in Joseph, to assume that he attempted to violate her whom by the angel’s revelation he knew to have conceived by the Holy Ghost.
“We must therefore simply assert that the Mother of God, as she was a virgin in conceiving Him and a virgin in giving Him birth, did she remain a virgin ever afterwards.”