An exhibition from another planet

It's one small step for art but a giant leap for the art world.

This is an exhibition which embraces the popular idea that contemporary art is alien and incomprehensible, then uses that idea to imagine an exhibition curated by a visiting Martian, before finally producing a contentious and ironic new understanding of contemporary art, light years away from the philosophies and theories which predominate.

Among the items in this radical and dense show is Damien Hirst's spot painting for the Beagle space probe. Beside it, a short gallery text explains that Martian interest in our art began when the Beagle crashed on their planet and they found the mysterious work in the wreckage.

Following that, the curator's story continues, a Martian was dispatched to Earth to study contemporary art. The exhibition and catalogue are the result of this trip.

This is the motivation for what is, on one level, a wide survey of contemporary sculpture.

It includes the greatest hits (a Jenny Holzer LED display, Piero Manzoni's tins of his own faeces), work by fine artists who aren't seen often enough in this country (there's one of Haim Steinbach's trademark minimalist shelves, this time with a plastic model of Star Wars' C-3PO and square digital clocks placed on top), plus a careful selection of pieces from young emerging artists, many British - from Francis Upritchard's voodoo sticks to Spartacus Chetwynd's lizard costume.

But the power and wit of the exhibition lies in its organisation, not its selection. This is a serious exercise in "reverse anthropology" - the application of Western ways of looking at other cultures.

The Martians behave just like 19th-century anthropologists (a time warp, perhaps?), dividing the works of art up according to the old classifications of tribal artefacts - "kinship and descent", "magic and belief", " ritual and communication".

Early in the show, one is greeted by Sherrie Levine's gold-plated version of Duchamp's urinal categorised as Ancestor Worship.

Further on, you will find Richard Prince's cowboys under Magic & Belief/Icons. The catalogue essay by author Tom McCarthy, in the guise of a Martian agent, adds another social dimension to the anthropology.

He marvels at the ritualised corruption and elitism of the art world and enjoys his newly acquired ability to see anything and everything as art.

And yet, this is more than an organisation of artworks in the style of an old-fashioned colonial museum.