IN REAL LIFE today, our sexual behaviour or activity is usually agreed to be a private matter; this is supported by the modern law, which prohibits public sexual acts. Public, here, usually means not literally ‘public’, but publicly visible, without any attempt at containment, since in many countries from time immemorial, one of the pleasures of sexuality is its impromptu occurrence amidst nature in secluded outdoor areas, in jungles, forests etc, or even in one’s house where an open window may permit observance from outside, yet the act is not being done in ‘public’ per se.
A profound change towards human sexuality began since BC, with the realistic depiction of nudity, heterosexual, oral, and homosexual sex acts painted on walls and pottery among the Greeks and Romans, while artists in India produced, along with small erotic paintings, the best erotic sculptures (not carvings!) of all cultures in antiquity which were as public as public can be on the sides of temples, doorways, etc.
The Chinese and Japanese mastered meticulously vivid erotic graphic art on the pages of popular books, predicting the comic book. These are the cultural forerunners of sexuality in the arts, and it is significant that these antique cultures of Mediterranean Europe and Asia were the first to define and associate the quality of being civilized with an appreciation of sexual expression in the arts, especially visual and literary art.
However, when we say these ‘cultures’, that does not mean the Greeks and Romans and Indians and Chinese and Japanese on the whole, but those individuals and social groups who placed great value on such art, and experienced a more contemplative and deeply satisfying relationship with their real life sexuality via an appreciation of such art.
The concept of ‘culture’ has been an evolving idea since the beginning of human society,  in which individual freedom  never stops or stagnates, and takes precedence over any historical inheritance or reflexive reactions to it.
The brilliant Afro-American novelist and essayist, Ralph Ellison once said in an interview titled ‘WHO SPEAKS FOR THE NEGRO?’ “One of the advantages of being a negro (post-emancipation) is that we have always had the freedom to choose or to select and affirm those traits, those values, those cultural forms which we have taken from any and everybody…we probably have more freedom than anyone, we only need to be more conscious of it.”
What Ellison implied was that many customs, influences, and skills imposed on negroes since slavery were converted by them into positive multi-faceted assets, interests, opportunities, and cultural adaptations later in the post-emancipation New World of the Americas.
But why should human culture develop in a direction where a large part of its artistic skills become dedicated to duplicating human behaviour on the whole? Indeed, it is the creation and appreciation of art which differentiates the human species from beasts.
Animals have no inclination to see themselves or be instructed from self-images, since they are guided by their instincts alone. Human civilization, on the other hand, preserved itself and advanced by developing various forms of artistic human duplication to celebrate customs, to instruct, or to guide. Even though early humans knew how to enjoy their sexual organs and reproduce their species, skilled duplication of sexual activities via artistic processes — first visual art then literature — multiplied the potential pleasure and stimulation of such acts by depicting and describing romantic and erotic moments, also methods or styles of sexual pleasure that were still unknown to many others anywhere.
In those cultures where the concept of art did not concentrate on depicting human bodies involved in sexual activities, or the expression of romance, visual art in particular, even when combined with dance and theatre, was more concerned with presenting the sexes, whether kings, queens, leaders, gods, or animals, as effigies, some majestic , but many in common everyday roles.
Tropical African sculpture, for example, was filled with stylized and adorned faces as exaggerated forms because its interest was  in cosmic ancestral spirits coupled with superstitious concepts, visualizing cults of fertility and fecundity, but not the depiction of the erotic moment or the sex act, since humans were not regarded as distinct from the mysteries of nature.
Nevertheless, the African, in general, came to be seen as instinctively sensual precisely because of this closeness to nature, which found more artistic sexual expression, however generalized, in modes of dance above all. Today, that has drastically expanded, and we have many ‘Afro’ magazines of an erotic nature with photographic depictions of the erotic beauty of black women and men.
The pre-Columbian cultures of the Americas shared a similar avoidance of the duplicated sexual act in sculpture and painting, but we should not think this is simply because these cultures had not developed the necessary three-dimensional skill of complex realistic imitation. These cultures simply did not have a dominant vision of art as realistic depiction. For instance, pre-Columbian North American Indian art is completely abstract and colour-field oriented, except for stylized masks, animal forms, and geometric dolls. Yet the Mayans and other native Indians of the Americas invented chocolate, which is a delicious human aphrodisiac linked to sexual pleasure. And the Egyptians, who, like the Mayans, sanctified the male sperm, drew numerous male profiles in stone with erect penises, upon which prudish Anglo-Victorian archaeologists and Christian missionaries used their hammers and chisels to disfigure or remove. Egyptian women in ancient Egypt were also the first to develop small, inserted objects — called IUDs today — as birth control devices,  and clearly also to seek only sexual pleasure.
The creation of sexual imagery in various forms of antique visual art served the purpose of developing human pleasure on an inner imaginative level, which began to refine the idea and experience of pleasure as separate from real bodily actions involving two or more people.
Since artistic imagery for all spectators is not corporal or real (even theatre  remains outside audiences, and the sexuality of the ‘Living Theatre’ of the 1960s was meant to be psychological and therapeutic by its spectator involvement), pleasure becomes a mental value which restrains yet satisfies the viewer, if not by self-pleasure, then by fulfilling the need for sensual arousal which is largely a self-satisfying tributary of the ego, or vanity attached to the release of bodily pleasure with a chosen individual via orgasm.
Sexuality in the Arts is a major contributor to a relaxed, educated social understanding of the normality of having sexual desires, and satisfying them without resorting to uncivilized predatory violence, such as rape, or the corrupt abuse of innocent minors.
A tradition, or adoption of sexual expression in the arts has therefore contributed to the achievement of such civilized values in many societies and nations today.