There had been naked depictions of Assyrians before the Greeks - you can see them elsewhere in the British Museum. But these were humiliated, naked victims of war, flayed and beheaded by the victors.
Unlike the Assyrians, Persians and Egyptians before them, the Greeks made heroes of the nude form. Greeks didn't actually fight naked in battle, nor did they stroll down Athens High Street in the nude. But the idealised human form, the uniform of righteousness and heroism, was the naked one.
It was in the naked form that man was thought to be in perfect balance. The mid-5th-century Discobolus - "the disc thrower", a Roman copy of which is in the British Museum's show - was said to require more mathematical knowledge of balance and stress than any previous statue.
Discobolus. Photo / Creative Commons
The body was celebrated in all its forms. Ancient vases show the black bodies of the Ethiopians (Greek for "burnt faces", the term for anyone from below the Sahara). Those Ethiopians fought for the Trojans under their king, Memnon, held up as the Ethiopian Hector.
It wasn't just men who were depicted in the buff, but gods, too. The Greeks would have been amazed by the Charlie Hebdo tragedy, and the row over depicting religious figures, fully clothed or otherwise.
Zeus, Apollo and Poseidon were regularly carved as nudes. The Greeks were more circumspect about naked women: Aphrodite was the only woman to be sculpted naked. In the exhibition, there's a nude Aphrodite - known as the Lely Venus, once owned by the 17th-century painter, Sir Peter Lely, now in the Royal Collection. This Aphrodite is a terrible flirt: completely naked, she crouches over, half-hiding her breasts and crotch from one side, leaving a pretty racy view from the other.
Lely Venus. Photo / Creative Commons
Fifth-century Athens produced a strange, unprecedented combination of artistic freedom and rigid artistic rules. Strict ratios governed the relationship between the height of columns, their width and the gap between them. On statues, the length of the torso was in precise proportion to the length of the line running at right angles to it, from nipple to nipple.
Still, the extraordinary thing was that you were allowed to see the nipples at all. The art historian Kenneth Clark said the nude "is an art form invented by the Greeks... just as opera is an art form invented in 17th-century Italy."
The Romans followed their lead - that's why so many original Greek bronzes, later melted down, are only known today thanks to Roman copies.
That Greek ideal of the naked body was celebrated during the Renaissance, too. Michelangelo based his naked Adam, on the Sistine Chapel ceiling, on the Belvedere Torso, a twisting, contorted fragment of an ancient statue of a naked male. The torso so influenced Michelangelo that it was nicknamed "The School of Michelangelo".
Belvedere Torso. Photo / Creative Commons
Before the Elgin Marbles came to Britain in the early 19th century, the Belvedere Torso was considered the ideal sculpture of the human form. That it had such influence was particularly striking, given the absence of a head. How brilliant, critics have said - of the torso and of Michelangelo's work - to portray emotion through stomach muscles alone.
How much were stone nudes supposed to titillate? When the writer Lawrence Durrell was at St Lawrence's School, Canterbury, in the 1920s, his Greek teacher brandished a photograph of a naked Venus de Milo, thumped his fist on his desk and barked, "What do you think they were trying to do? Make us tingle with lust? Certainly not! They were asking themselves what beauty is, and whether it lies in proportion."
Venus de Milo. Photo / Creative Commons
It's hard not to see an intensely sexual element in some more sensuous sculptures, like the Nereids from the 390BC monument in Xanthos, in modern Antalya, Turkey. These sea nymphs, now in the British Museum, appear to be sprinting into a headlong gale, their thin gowns plastered against their chests by the wind and rain - the first wet T-shirt competition.
In earlier Greek sculptures, the sexual element is even more graphic. The earliest known representation of a mythical figure is a 3in tall, mid-eighth century BC statue of a naked Ajax.
Ajax, the strongest Greek, is deeply depressed at losing Achilles's armour to Odysseus, after the wily Odysseus is characteristically more eloquent in staking his claim to it. And so he falls on his sword - a rather delicate operation since he is in a state of, erm, extreme excitement.
For decades, supposedly obscene treasures such as little Ajax were stuffed away in the British Museum's "Secretum" - the name for the ultra-secret Cupboard 55. It was only in the 1960s that the Secretum was opened up; only half a century ago that we caught up with the Greeks' astonishingly avant-garde approach to naked beauty.
• 'Defining Beauty: The Body in Ancient Greek Art' opens at the British Museum on March 26; britishmuseum.org
