The zoomorphs are what the hapless English academic Jeremy Pordage first notices when he arrives in California in Aldous Huxley's novel After Many a Summer Dies the Swan. As he is chauffeured toward Huxley's parody of Hearst Castle, Pordage sees whole buildings shaped like dogs and sphinxes, and is duly appalled at the ghastliness of it all.
Now the zoomorphs are back, and the height of architectural good taste. Some of the world's leading architects, such as Frank Gehry and Santiago Calatrava, routinely incorporate enormous forms of fish and birds into their buildings. The most technocratic of British architects - for example, Wilkinson Eyre, winners of the Stirling Prize (architecture's equivalent of the Turner Prize) for the past two years, and Marks Barfield, the creators of the London Eye - are letting loose animal edifices in our cities. Even Norman Foster's 40-storey office tower for Swiss Re in the City of London, the building dubbed the "erotic gherkin", turns out to be more animal than vegetable. Foster is not sure about a zoomorphic "movement", but he admits: "Structural form in some cases may be more fluid - or 'organic' - than in others."
Some architecture critics dismiss the new zoomorphic trend as a joke in poor taste. True, it's kitsch at times, but don't write it off completely. There is a long tradition of representing natural form in human culture, even if in architecture these flowerings have tended to be rather ephemeral. At the beginning of the 21st century, there is reason to think that it might endure. Buildings such as the armoured blob that is Future Systems's design for the new Selfridges, which opened in Birmingham on 4 September, or the Butterfly House that Laurie Chetwood has just built for his family near Godalming, Surrey, are where architecture is heading. "The organic has always been appropriate," says Jan Kaplicky of Future Systems. "It's just not always been used."
Animal forms have always added some of the deepest layers of meaning in architecture. The "Zoomorphic" exhibition at the Victoria and Albert Museum includes architectural models of two Aborigine visitor centres in Australia, one in Victoria, the other at Uluru (formerly known as Ayers Rock). The architect of both buildings, Gregory Burgess, developed the designs in workshops with the local communities, incorporating into the architecture cockatoo and snake motifs based on their totemic symbols. These are just the sorts of places where you might think animal symbolism is appropriate - representing the building's "primitive" culture, or "spiritual" purpose.
The surprise is to find that we're still doing it. We have airport buildings - the best known of which is Eero Saarinen's TWA Terminal in New York, but also now Calatrava's train station at Satolas, Lyons - made like huge concrete birds' wings. Meanwhile, challenging new architecture planned for the British seaside is based on marine life. Sn0hetta's Turner Centre in Margate will look like a shark's fin rising up out of the sea. Ushida Findlay's Stade Maritime visitor centre in Hastings, East Sussex, flops about like a freshly landed catch. These buildings will be built.
One that won't is a proposal to redevelop the breakwaters at Morecambe. Its architects, Birds Portchmouth Russum, paid homage to the local delicacy with a string of extravagant constructions like shrimp: a theatre, a lifeboat station and so on, the tallest of them roughly 40 storeys high. "They would be seen from the Lake District," says Mike Russum. "The breakwaters are at the scale of Morecambe Bay, not Morecambe, and the rhetoric was one of regeneration." Their inspiration was Blackpool, not far away. The buildings would have contained their share of architectural jokes, with references to constructivism, Isambard Kingdom Brunel and much else besides. But mainly, they would have had immediate appeal because they were recognisable above all as animals.
Many factors are converging to make zoomorphic architecture right for the times. One is simply that it is permissible. The old rules of architectural ideology have been abolished. You no longer have to be a modernist or a postmodernist, building flat roofs or pediments accordingly. You can build what you like as long as you can make it stay up.
The need for buildings to stay up has been one of the main things constraining their shape: gravity likes a vertical wall. But sophisticated design programs now allow architects to imagine buildings of almost any shape on their computer screens. Frank Gehry uses software adapted from military applications to create his fish-buildings. And there are creative structural engineers prepared to work with these architects and indulge their fancies. Other practicalities have also limited the shape of buildings. A facade that is entirely glazed, for example, must be of such a shape that you can gain access to the glass for cleaning. But the recent development of self-cleaning glass - coated with a non-stick film - makes this a problem of the past. There are other, similar developments in the pipeline that will help make wild shapes increasingly cost-efficient.
Alongside these innovations, there is a cultural shift encouraging architects to evoke natural organisms. Astute businesses no longer talk about re-engineering (a brutal, nuts-and-bolts approach to change) but about adaptation and evolution. Art and fashion have fallen out of love with the machine and have returned to the body. In short, biology - its language and its imagery - has spread into the cultural discourse. The phenomenon is especially obvious in advertising, where one car brand is advertised with the stripes of a DNA test, while another morphs into fish swimming along the road and into a petrol station. The media expert Professor Steve Jones, head of the department of communications at the University of Illinois, was even persuaded to describe one car as "genetically engineered".
All of these factors are significant, but it is the convergence from such different directions - ideological, technological, cultural - which makes it likely that, this time around, zoomorphism will be more than a passing fad. Zoomorphs are no longer the kitsch creations of eccentrics with dubious taste, constructed in places untroubled by planning regulations, as they may have been in Depression-era California.
Art nouveau was the first full-blooded architectural movement to take on the natural world - a movement that might not have arisen at all without the growth of zoos and botanical gardens during the 19th century, bringing exotic flora and fauna to the western gaze for the first time. Today, we learn about the natural world thanks to David Attenborough, and the catalogue of zoomorphic forms runs through all the phyla of the animal kingdom.
For practical reasons, the art nouveau impulse to celebrate nature could not be followed through. Relatively few buildings were built in the style. For most, it proved too expensive to cut each piece of glass or bend each piece of wrought iron by hand to create the desired effect. Now, architects are once again sufficiently unhampered by stylistic dogma to experiment. And their computers have the power to connect the drawing board directly with the factory floor, so that the fancy-shaped parts they need in order to assemble buildings with complex forms can be made automatically and cost-effectively.
In art nouveau design, animal and plant motifs were essentially elements of a decorative style. Today's zoomorphic forms, however, are sometimes justified on functional rather than stylistic grounds. Why should a purely functional building look like anything? "It's not inspiration," insists Chris Wilkinson of Wilkinson Eyre, architects of the popular "blinking eye", the Gateshead Millennium Bridge. "We see parallels." This subtle difference is crucial. These architects are not looking to nature for ideas; they are having ideas, and then finding (sometimes unexpectedly) that nature has had the idea earlier.
Take Norman Foster's Swiss Re tower, which in fact bears such a close analogy to a sea sponge that the gherkin label should be dropped for good. The class of sea sponges known as glass sponges has silica exoskeletons that resemble Foster's building in overall form. But the analogy runs deeper than mere appearance. It is structural, too: the three-way lattice of steel beams that forms the structural frame of the Swiss Re tower is clearly echoed in the delicate structure of the sponge's exoskeleton. Even the building's ventilation system replicates the way that these sponges circulate water to extract nutrients. Curiously, Foster did not need to know any of this for his building to come out the way it did.
Hugh Aldersley-Williams is the curator of "Zoomorphic: new animal architecture" at the Victoria and Albert Museum, London SW7 from 18 September 2003 to 4 January 2004. For more information call: 020 7942 2209/2211 or visit www.vam.ac.uk. His book to accompany the exhibition is published by Laurence King (£19.95)