Modern British Sculpture, Royal Academy

Austere, elegant, impressive. Edwin Lutyens’s Whitehall Cenotaph is a thing of beauty, a monument that embodies permanence in the face of all that is impermanent, and solidity in the face of all that is ephemeral. It’s an inspired decision to bring it indoors, for inside a hushed gallery, away from the rush of traffic and stripped of its flags and sculpted wreathes, Lutyens’s memorial can at last be properly admired as a work of art.

Of course, it’s only a replica, three-quarters the size of the original. But it seems less of a reproduction, more of a ghostly doppelgänger, its sheeny plaster surface making it resemble one of Rachel Whiteread’s inside-out casts. But it's certainly more stirring and dramatic than anything made in recent years by Whiteread, who happens to be just one of the artists controversially omitted from this survey.

What makes Lutyens’s monument even more evocative are the mournful chorus of shadowy figures that surround it. Hanging high-up in the rotunda gallery, are eight grainy, full-scale black-and-white photographs of plaster figures carved by Jacob Epstein. Depicting the cycle of life, these figures were originally commissioned for the British Medical Association’s building in The Strand, but were taken down in 1937, less than 30 years after being erected. This was probably due to severe erosion and not, as may once have been thought, because of the confrontational nature of the nudity of the figures, which is certainly no more “shocking” than what you’ll find in Classical Greek statuary, and much less so than in Epstein’s monstrous Adam, 1938, with its huge swinging cock and pendulous balls. This much later figure can be seen striding forth in evident existential despair in a gallery by itself three rooms down.

Both Lutyens’s monument and Epstein’s frieze-like figures are a fitting way to open an exhibition which has seen sculptural form of the 20th century punctured, ruptured and imploded. They offer a point in which sculpture starts to veer in directions that could never have been foreseen by either artist, both of whom look back at different points in history, as well as forward by breaking with well-worn conventions. The audacious, often puzzling turns this exhibition takes are no less startling than that first room.

In The Establishment (each room is given a title clearly meant to challenge as well as inform) we’re presented with the work of four past presidents of the Royal Academy. This includes arch Victorian sculptor Albert Gilbert, a figure usually neglected by such surveys, intent as they are upon forwarding a thesis which demonstrates a linear, uninterrupted march towards Modernism. The elaborate conical form of Gilbert’s 1887 Jubilee Memorial to Queen Victoria echoes that of Phillip King’s purple-coloured plastic Genghis Khan, 1963 (pictured right), a work that manages to look equally bizarre, pompous and somewhat ridiculous several decades on.

And then we emerge into the darkened space of the third room, by far the most seductive and brilliant in the exhibition. Here ancient ethnographic works from the British Museum are juxtaposed with Modernist sculptures by artists both familiar and largely forgotten, each of whom were inspired by "the primative". A frieze depicting battle victims of World War One by Charles Sargeant Jagger hangs between two Assyrian battle friezes; a painted seductress in a towering headdress by Eric Gill is neighboured by a voluptuous, and far more seductive, second-century Indian nature-goddess; and the surviving forepart of a magnificent running leopard from Halicarnassus (c 350 BC) is displayed next to a squatting Sun Goddess by Epstein. Many of these are ancient works that could pass for modern and some are modern that could easily pass for ancient. It’s an impressive room, but, for me, most memorable of all is the anxious and tender Vancouver Island Mother and Child (pictured above left), dated mid to late 18th century. One feels that this precious and beguiling figurine could have been made during almost any point covered by this exhibition's vast historical reach.

Elsewhere, Anthony Caro’s seminal 1962 Early One Morning (pictured right), which is one of the earliest British sculptures to break with so-called British “parochialism” and look to America, predictably makes an appearance, as do pieces by Damien Hirst (a huge vitrine featuring a stinking picnic containing raw rotting meat, a cow's head and a swarm of crawling flies), Sarah Lucas, Jeff Koons, Carl Andre (the infamous bricks), Rebecca Warren (main picture) and Tony Cragg (though not Richard Deacon, who is nearly always mentioned in the same breath as the latter, as if the two artists were conjoined twins).

But so much that we might expect from this exhibition doesn’t appear, and so much that we don't does. Indeed, this is quite an easy exhibition to tear apart if you overthink it, for there seems rather little to hold it together apart from the enormous fun to be had in making connections. It's beautifully and cleverly put together - the discursions and juxtapositions all work extremely well - it’s just that its overall rationale is neither very clear nor particularly convincing. Why, for instance, include one of Gustave Metzger’s silly agitprop newspaper assemblages and not one of his seminal auto-destructive paintings? And much has been made of the exclusion of Anish Kapoor and Antony Gormley. I don't miss them, though there appears to be neither rhyme nor reason for overlooking them. Nor for ignoring Eduardo Paolozzi, or the stream of post-war Geometry of Fear sculptors such as Reg Butler.

Post-Modern in conceit, this exhibition seems to be making a fetish out of not bowing to the definitive overview. Though that conceit threatens to become wearisome (why a whole room devoted to ceramics? It is by far the dullest in the exhibition), this is still a survey which, amazingly in fact, pulls off something special and quite rare. For all its perceived flaws it manages to convey enormous energy and brio. And to get it, you really have to go and see it for yourself, not wait for a convincing argument.

• Modern British Sculpture at the Royal Academy until 7 April
• Buy Modern British sculpture catalogue on Amazon