‘At last!’ was my first reaction to this book: at last a scholarly treatment of a subject I’ve been noticing, pondering and mentally anthologising for much of my life. It’s partly a gay thing, no doubt, to clock the backside of a marble Jason or painted gondolier, surfaces and volumes that polite analysis seems not to register, and to speculate about those artists seemingly fixated by them. In his diary in 1907 E M Forster jotted down a list of names suggesting a sort of gay lineage – Pater, Whitman, Housman – and added ‘Luca Signorelli?’ I assume he had seen his frescoes in Orvieto Cathedral, in which the naked male backside is a pivotal feature, and jumped to his own conclusions.

In Seen from Behind, Patricia Lee Rubin pays much attention to Signorelli and is no doubt properly circumspect about outing him: sexual mentalities in 1500 are not to be crudely submitted to 21st-century models. But then, if Signorelli wasn’t in some sense gay, what did his focus on the male backside mean, to him and to his contemporaries? Of course, Renaissance art revived the idealised bodies, male and female, of the classical world. The naked male figure soaked up meanings, conveying ideas of both physical power and divinely inspired grace. At the same time, art granted a licence to look at, and appreciate, things concealed by social convention. The heroic male nude could not, I think, be used today to signify civic pride and glory, as it was when Michelangelo’s David was placed at the entrance to the Palazzo della Signoria in Florence, or when the Foro Italico was laid out in Rome four centuries later. Fascism has polluted it, feminism questions it, irony and pornography undermine it. Recapturing its earlier meanings is a complex task.

Take The Massacre of the Innocents by Cornelis van Haarlem, which dominates one of the magnificently refurbished galleries of the Rijksmuseum. Painted in 1590, it is a scene of tumultuous violence, anchored formally by the massive nude figures of four soldiers in the foreground, one striding towards us from the right with a dead baby under his arm, one flat on his back on the left, overcome by a group of mothers, who gouge out his eyes. Counterpoised in the centre are two soldiers seen from behind, one standing, the other, biggest of all, down on one knee as he cuts a child’s throat, his colossal backside not only in the viewer’s face but also inches from the face of the child’s desperate mother. The heroic scale of the picture, some eight feet by twelve, adds to the interpretative puzzle for a modern eye: why make a vast male arse the focal point of a major religious painting? It’s impossible, too, not to wonder if the Dutch, whose art embraces the everyday, the suggestive and the downright lewd, kept a straight face about it, then and afterwards.

Rubin doesn’t mention Cornelis – she focuses mainly on painters and sculptors of the Italian Renaissance and their work, from a stooping labourer in a Giotto fresco turning his backside towards Christ to Michelangelo’s insistence on seeing the male nude, in two or in three dimensions, from every conceivable angle. One of her themes is that though the male bottom may be sexy, its baring had long been a sign of derision (as in mooning), with certain vernacular meanings – in one Signorelli mural, the Devil, whom the artist shows tempting a pilgrim, has his leggings down to show his tight white underpants, ‘embodying the expression andare a fare in culo – go to Hell’. Rubin notes too that in the 15th century military costumes became far more tightly fitting, inviting eroticised display; St Bernardino of Siena explicitly attacked such dress as ‘invitations to sodomy’.

She also notes early on the favouring of a back view, be it clothed, nude or semi-nude, for executioners and other agents of violence, such as the flogger of Christ in Mantegna’s unsparingly harsh depiction of the Flagellation. In this unfinished engraving, Mantegna’s sculptural manner allows some uncertainty as to what is flesh and what underwear as the torturer’s hose drops round his lower legs and his shirt rides up. When the face, with all its expressive power, is averted and arms are raised, the physical pivot of the backside assumes a heightened expressive value. This is a lowlife or hired thug, his conscience as disposable as his breeches, his injury to Christ compounded by the insult of his baring his buttocks to us. But he is also a beautiful and virile figure. Two conceptions of the male backside, the derisory and the idealised, seem to coexist in Mantegna’s depiction of him.

Rubin examines the eroticisation of Donatello’s David, created, she insists, with no intention of arousing illicit desire, but ‘queered’ by Horst Janson in the 1950s – the formidable John Pope-Hennessy thought Janson’s teasing-out of homoerotic meanings had left a ‘trail of slime on a great work of art’. But homoerotic exploration clearly had its part in the sophisticated court culture of 15th-century Florence. The latent queerness of Donatello’s work was surpassed in the final years of the century by the unignorable sensuality of Michelangelo’s marble Bacchus, one of the first monumental nudes of the Renaissance, showing a youth on the brink of manhood, upright but teetering with drink, and designed to be seen in the round, the back view (with a hidden satyr’s head aligned with Bacchus’s left buttock) as important as the front.

Seen from Behind doesn’t seek to be so panoptic. It is a series of reflections on the ‘dramatic range’ of the male bottom – as Rubin wittily notes, in the Sistine Chapel, God himself shows his rump as he whisks away ‘to create the earth, while virtually mooning the fresco’s beholders’. Now and then we leap forward, to find a memory of Donatello’s David in a naked swimmer of Thomas Eakins or of Michelangelo’s cartoon for The Battle of Cascina in Cézanne’s bathers – Michelangelo’s ‘muscle-bound behinds’ were to be an inexhaustible school for other artists. Rubin offers many valuable insights on what Lucian Freud called the ‘emotional vocabulary’ of the naked body and the resonance and recurrence of postures: hands on hips, legs astride or prone with the buttocks raised. But there is more to be said, and Rubin herself would probably agree that she has opened up a wonderful subject without completely getting to the bottom of it.