Thank you as always for a very stimulating article Christopher.
My own present understanding is that the moral manipulations/distortions that the Catholic church implemented as the centuries progressed, moving further in time and reality from the original teachings brought by Christ, were amplified by the so-called "discovery" of perspective, and the excited exploration and mastering of this artistic device that then unfolded and began to dominate artistic work in western Europe.
Icons and earlier works depicted the scenes of Christ's life events, the saints and disciples etc., in a non-realistic style, using devices like "anti-perspective" and differences in scale, very deliberately, for the simple reason that they were not illustrating the physical realm we live in.
The symbolism of human figures, buildings, caves, mountains, mythical and real animals, and the hand of God were used to convey descriptions, instructions and the meanings inherent of the inner life; the psychological struggles and conditions of following a spiritual discipline, which all religious art does (or in their origins do). But this insight and understanding was gradually eroded away in the Catholic tradition (not in the Eastern Orthodox Church) as the predominance of reason and logic took over from the heart, and actual spiritual work. (I mention the heart not as a symbol of emotionality, but of conscious love.)
Icon painters (who were monks) knew and understood perspective very well, but it was not the best device for the task at hand: the illustrating of the inner life. And as they were not just painters but students of a spiritual path, the meaning behind what they were painting was an integral part of their theological/philosophical enquiry, and so was not something that needed to be explored. The icon painters' focus was and still should be, their inner practice of devotion while practising the act of painting.
But paintings began to be made by artisans who were not deeply involved with a spiritual teaching, they were just skilled painters/workmen, though they may have been devout church goers, and as the increasing interest with perspective, which became an obsession, took over, the discipline of exploration began transitioning from the painter's inner world, to the outer world, and to the transient appearance of things. All sorts of nuances came into play for an artist, like having to earn a living, rather than living and working in a monastery. Which as you can imagine, leads to many artistic and often moral and idealistic compromises. (I speak of this as a practising artist of 40 years.)
From the perspective of the spiritual in art, the Renaissance was a terrible mistake with dire long-term consequences on the psyche of artists, and therefore upon the European population as a whole, due to the far-reaching, often subtle, influence of the visual arts. Exploration of the external world and the mental games of rationalism blossomed, which began being manifested into everyday life as: the growing need to conquer other parts of the world, subjugate other peoples, and later on the absurd notion of even conquering Nature (whatever that means), which has led us to a rather desperate state of play in modern times.
So... Mary's breasts, symbolic of so much, on so many levels, from the mundane to the profound, fell victim to this whole process. Even the positioning of the breast near the collarbone almost certainly, originally had some symbolic meaning, because in icons nothing is left to accident. As with the naked (but modesty-covered with his long beard) John the Baptist, the erotic was not given a chance to influence the thoughts of the devout, but as external realism began to take over and the whole nature of art was adapted to a more commercial world, the papacy had to adapt and purge certain imagery that would not suit the new artistic style. A style which saw the gradual extinguishing of an aspiration to the sacred, and an increasing celebration of the commercial and profoundly meaningless that we witness today.
