The Sibyls were prophetic women who were resident at shrines or temples throughout the Classical World. The five depicted here are each said to have prophesied the birth of Christ. The Cumaean Sibyl, for example, is quoted by Virgil as declaring that “a new progeny of Heaven” would bring about a return of the “Golden Age”. This was interpreted as referring to Jesus.
In Christian doctrine, Christ came not just to the Jews but also to the Gentiles. It was understood that, prior to the Birth of Christ, God prepared the world for his coming. To this purpose, God used Jews and Gentiles alike. Jesus would not have been born in Bethlehem (where it had been prophesied that his birth would take place),except for the fact that the pagan Roman Emperor Augustus decreed that there should be a census. Likewise, when Jesus was born, the announcement of his birth was made to rich and to poor, to mighty and to humble, to Jew and to Gentile. The Three Wise Men (the “Magi” of the Bible) who sought out the infant King with precious gifts were pagan foreigners.
In the Church of Rome, where there was an increasing interest in the remains of the city’s pagan past, where scholars turned from reading Medieval Church Latin to Classical Latin and the philosophies of the Classical world were studied along with the writings of St Augustine, the presence, in the Sistine Chapel of five pagan prophets is not surprising.
It is not known why Michelangelo selected the five particular Sibyls that were depicted, given that, as with the Minor Prophets, there were ten or twelve possibilities. It is suggested by John O’Malley that the choice was made for a wide geographic coverage, with the Sibyls coming from Africa, Asia, Greece and Ionia.
Vasari says of the Erythraean Sibyl “Many aspects of this figure are of exceptional loveliness: the expression of her face, her headdress and the arrangement of her draperies: and her arms, which are bared, are as beautiful as the rest.”-Wikipedia