Jake and Dinos Chapman: The brothers grim

To be truly contemporary you must have a good grasp of history, since it is perhaps only by looking back that you have a sense of where you are. It is in this that the Chapman brothers excel. Their work never leaves the past. Instead, it revels in it - in reheating old masterpieces by dead artists, in rolling in the ink and paint and dust of the past - and in being able to smile while doing so.

The smiles on the works submitted by Jake and Dinos Chapman to the Royal Academy's Summer Exhibition this year are freakish, yes, but then we have learnt to expect that following the brutal recasting of Goya's Disasters of War (1993), the salacious pseudo-porn films - Bring Me the Head of ... (1995) - the mutant mannequins with their rash of penises, vaginas and sphincters - Tragic Anatomies (1996) - and the rest. This time, though, the genteel sensibilities of visitors to the Summer Exhibition need not be disturbed, although the sharper among them will sense that something subversive is afoot.

The Sleep of Reason consists of a canvas resting on an artist's easel. The face painted on the canvas resembles a demon meerkat auditioning for a job as a clown, but clowns, as all viewers of horror films know, are never funny or kind. The other piece accepted for the exhibition, entitled The Marriage of Reason and Squalor II, looks like a pile of wet clay - its wetness imploring us to touch it, to bring our own intentions to something that, for all the artists' supposed tomfoolery, looks unfinished, unresolved. An elephant's head and a pig's head have been crudely modelled out of the clay. It is unclear whether the artists intend these to serve as self-portraits. That both sculptures are in fact made entirely out of bronze - the canvas, the easel, the modelling stand, the clay; only the paint is paint, but then paint is also camouflage - is, as Jake Chapman tells me, "absolutely duplicitous".

Both pieces directly reference painting and sculpture, two activities traditionally upheld by the Royal Academy: a bronze sculpture of the Academy's first president, Sir Joshua Reynolds, holding his artist's palette, stands in the entrance courtyard, after all. "The RA's view about a work of art is quite fundamentalist," says Jake. "Art" - he voices the capital letter - "should be about materials. Both our pieces are works of art that are pretending to be something else. In this, they undermine the fundamental laws of modernity with its insistence that a work should display its materiality in order to be truthful."

Both pieces are subtle acts of disguise. It's mystifying that only one of the works - the lookalike pile of clay - should have won the brothers the prestigious Charles Wollaston Award (it nets them £25,000, £5,000 more than the Turner Prize, for which they are nominated this year), when both pieces seem to work so much more powerfully together.

Jake, 36, and Dinos, 41, take great pains to deflect questions as to who does what in their artistic endeavours, so perhaps in the instance of this award binary recognition is irrelevant. The younger brother is always careful to use the plural "we" when replying to questions: "We are trying to avoid that notion of individualism," he says and will not be drawn on their family background. As to the recent attack on him by the Windsor Castle "comedy terrorist" Aaron Barschak - the artist was doused with red paint and thumped - Jake is dismissive: "It was so cheap. If he was able to blow the royals up, why didn't he?"

This apparent naivety about the inevitable ricochet of fame is not entirely believable since the Chapmans have become the must-have darlings of the avant-garde. With Charles Saatchi paying £1m for their latest installation - The Chapman Family Collection - a cruelly brilliant rendition of McDonald's advertising - and smooth British ambassadors eager to hang their piratic skull-and-crossbones prints on smart embassy walls, they now stride the panelled corridors of the establishment.

All this is a far remove from the days when they were just a couple of artists in an experimental bunch at the "Sensation" exhibition at the Royal Academy in 1997. They want their early life to remain a closed book, refusing to divulge details of their upbringing. When the most basic, banal biographical information first emerged in 1999 - grew up in Cheltenham and Hastings; father then an art teacher, now a vet; mother Greek-Cypriot; went to state schools - they were very annoyed. Later, they both studied at the Royal College of Art, graduating in 1991.

It was touch and go whether they would make it big, even after the shock success of "Sensation". Then the Royal Academy followed this with "Apocalypse" in 2000, at which the brothers' massive sculpture Hell was displayed.

"I remember going to see it in their studio," says artist Anthony Green, a Royal Academician and a judge of this year's Charles Wollaston Award, "and thinking we had to have it in the Academy immediately. I think it is still one of the most important figurative contemporary sculptures in the world."

The work's controversial depiction of a nightmarish world on the brink of collapse, with its 5,000 Nazi-costumed figurines in various stages of brutal murder and cannibalism, was too strong for some. But, as Norman Rosenthal, exhibitions secretary, points out: "You had to admire how exceptionally well-made it was. This is the central paradox of their work - it focuses on very brutal things but is so beautifully made. Their work is anti-art while playing on its own aesthetics. It's evidence of a very learned, very intelligent strategy."

This delight in scoring high intellectual marks shows in the books the Chapmans produce, although it is Jake who writes them. Dinos, he says, "is too busy looking after his family to write". Jake's first tome, Unholy Libel, was an intriguing mish-mash of ideas; his next, Meatphysics, its seemingly mis-spelt title suggesting a bloody apologia for their body of work, is out this September. He quotes the German philosopher Martin Heidegger's maxim that "language speaks man" as a way of explaining his view that the notion of authorship, especially artistic authorship, is grossly overrated. Possibilities, he says, are merely made possible by people, rather than essentially emanating from them. He praises science for its (supposedly) rationalist objectivity, its detachment from man.

On the face of it, their perspective isn't that optimistic, although Jake disassociates any sense of despairing personal biography from their work. "All art seems to be infected with notions of psychoanalysis and illness. The relationship between artist and viewer is projected as that between a patient and his therapist, that somehow what the artist produces is just his latent ego making itself manifest."

The brothers say that they revel in their own pessimism and their work's misanthropy. But what interests them most is distorting the idea of perfection. "There's this general assumption made about art today that there's been this shift from technical skill to a philosophical skill, that the idea is more important than the production of the work," says Jake. "We think we're more conceptual in that we also drag the notion of skill right into the centre of the debate." And this, from the artists who, the tabloids were saying, had just won a prize for something that looked like a pile of clay.