What are the earlier references to Mary?

The earliest reference is the miraculous painting of St.Luke on the Advocata Nostra year 50AD.

Advocata Nostra, the oldest icon of Mary in Rome, can be traced back to Jerusalem, where it was painted by St Luke after the Resurrection. Tradition has it that after he sketched the outline, the image of Our Lady appeared on it. No human hand was involved.

The other one is the Our Lady of the Pillar, the First Marian approved apparition in year 40AD.

The First Marian Apparition in Church History: Our Lady of the Pillar https://www.catholiccompany.com/getfed/first-marian-apparition-our-lady-pillar-5905

Mary was portrayed as the "another Advocate" here of the Apostles like Jesus role as the "First Advocate".

The biblical reference of Mary as the "another Advocate" was first experienced by Apostle Peter when he betrayed Jesus Christ his repentant heart lead him to seek the help of the Theotokos. Peter was able to rise-up and learn how to comfort a fallen Apostle and in turn Peter becomes the advocate to the Apostles as Jesus assigned this role to him in Luke22:32.

While in contrast, Judas did not seek the help of the Theotokos the "another Advocate" that led him to be overtaken by satan malice and had taken his own life by suicide.

"In His eagerness to show you,mercy, God has given His Son as your Advocate. And then to make your confidence even stronger, He has given you "another Advocate', who obtains through her prayers whatever she asks.Go to Mary, and you will see salvation. -St.Alphonsus Ligouri

What are the earlier references to Mary?

Belief in the incarnation of God the Son through Mary is the basis for calling her the Mother of God, which was declared a dogma at the Council of Ephesus in 431.

Development of Marian doctrine

The theological development of devotion to Mary begins with Justin Martyr (100–165) who articulated Mary’s role in salvation history as the Second Eve. This was followed up by Irenæus, whom Herbert Thurston calls "the first theologian of the Virgin Mother".

The Church's magisterium has identified four teachings about Mary as dogmas of faith. These include belief in her virginal conception of Jesus, taught by the First Council of Nicaea in 325. The Council of Ephesus in 431 applied to her the description "Mother of God", (Theotokos). The perpetual virginity of Mary was taught by the ecumenical Second Council of Constantinople in 553, which described her as "ever virgin", and was expressed also, by the Lateran synod of October 649. The doctrine of the Immaculate Conception states that from the first moment of her existence Mary was without original sin. This doctrine was proclaimed a dogma ex cathedra by Pope Pius IX in 1854. The dogma of the Assumption of Mary, defined by Pope Pius XII in 1950, states that, at the end of her earthly life, she was assumed into heavenly glory body and soul. - Veneration of Mary in the Catholic Church

The Sub tuum praesidium is the oldest preserved extant hymn to the Blessed Virgin Mary.

Sub tuum praesidium

"Beneath Thy Protection" (Greek: Ὑπὸ τὴν σὴν εὐσπλαγχνίαν; Latin: Sub tuum praesidium) is a Christian hymn. It is the oldest preserved extant hymn to the Blessed Virgin Mary as Theotokos. The hymn is well known in many Roman Catholic, Eastern Orthodox and Oriental Orthodox countries, and is often a favourite song used along with Salve Regina.

The earliest text of this hymn was found in a Come the Coptic Orthodox Christmas liturgy. The papyrus records the hymn in Greek, dated to the 3rd century by papyrologist E. Lobel and by scholar C.H. Roberts to the 4th century. According to scholar Serafim Seppälä "there are no determinate theological or philological reasons to reject the 3rd century dating."

There is a pious tradition that holds that, in the early days of Christianity, the Apostles of Jesus spread the Gospel throughout the known world, with St. James the Greater evangelizing in modern-day Spain. He confronted great difficulties in his missionary efforts and faced severe discouragement. In AD 40, while he was praying by the banks of the Ebro at Zaragoza, Mary bilocated from Jerusalem, where she was living at the time, and appeared to James, accompanied by thousands of angels, to console and encourage him.

Some of the earliest archaeological evidence of Marian devotion in Zaragoza is found in Christian tombs dating from Roman days, which appear to bear images representing the Assumption of the Blessed Virgin. In the 4th century, the presence of votive images placed on columns or pillars is attested. The oldest written testimony of devotion to the Blessed Virgin in Zaragoza is usually identified as that of Pedro Librana in 1155. There is evidence that the site attracted pilgrims from across the Iberian Peninsula during the 13th century, e.g. reflected in the work Milagros de Nuestra Señora by Gonzalo de Berceo, dated to the 1250s or early 1260s. The appellation Santa María del Pilar is attested for 1299. The claim that the first church had been the oldest in Hispania, built in AD 40 by James the Greater, is first recorded in 1318.

According to tradition Mary appeared to St. James on January 2, 40 AD. Spain celebrates this event on October 12 each year.

Tradition also says that St. Luke painted icons of Mary.

Though not included in the canonic pictorial of Mary's life, the scene became increasingly popular as Saint Luke gained his own devotional following as the patron saint of artists in general, and more specifically as patron saint of the Guild of Saint Luke, the most common name of local painters' guilds. The legend of Saint Luke as the author of the first Christian icons had been developed in Byzantium during the Iconoclastic Controversy, as attested by 8th century sources. By the 11th century, a number of images started being attributed to his authorship and venerated as authentic portraits of Christ and the Virgin Mary. In the Late Middle Ages and the Renaissance, Luke's ascendancy paralleled a rise in status of painters themselves, whereas before the Renaissance, sculptors' guilds and their associated craftsmen — which also included masons and architects, as all worked with stone — tended to be regarded more highly than painters. - Saint Luke painting the Virgin

More about the icons attributed to St. Luke can be seen in the following article:

Various traditions claim the Gospel writer drew one or more portraits of the Virgin Mary from life.

Mary, as the mother of Jesus, is documented in Roman catacombs: paintings from the first half of the 2nd century show her holding the Christ Child. Excavations in the crypt of St Peter's Basilica uncovered a very early fresco of Mary together with Saint Peter. The Roman Priscilla catacombs depict the oldest Marian paintings from the middle of the 2nd century: Mary is shown with Jesus on her lap, a standing man with tunic left hand a book right hand a star over his head symbol of messiahs. Priscilla also has a depiction of the annunciation. Early veneration

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Earliest fresco of the Virgin Mary, Catacomb of Priscilla, 2nd century.